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Efeito do Sombreamento sobre o Teor de Clorofila e Crescimento Inicial do Jequitibá-rosa
Abstract
Com o objetivo de avaliar os efeitos de períodos de sombreamento sobre o crescimento inicial e concentrações de clorofila em mudas de jequitibá- rosa (Cariniana legalis), foi instalado um experimento no viveiro de pesquisa da Embrapa Florestas, em Colombo, PR. O delineamento experimental foi o de blocos ao acaso, com cinco tratamentos e quatro repetições. Os tratamentos estabelecidos foram: 100 % (pleno sol); 70 %; 64 %, 44 % e 34 % de radiação solar incidente. A altura e diâmetro do coleto foram monitorados em intervalos de 30 dias, dos 60 aos 180 dias após a emergência (DAE). O peso da matéria seca total, aérea e radicial, área foliar, clorofila a e b e clorofila total, foram medidos aos 180 DAE. O percentual de 63,07 % de RFA (radiação fotossinteticamente ativa) proporcionou o maior crescimento em altura das mudas. As maiores médias de diâmetro do coleto ocorreram com as mudas submetidas a pleno sol. O oposto foi observado com a área foliar, onde observaram-se as maiores médias quando as mudas foram submetidas ao maior percentual de sombreamento (34 % de luminosidade). O acúmulo de matéria seca total foi estimado para 54,40 % de RFA. Os teores de clorofila a e b foram maiores nas folhas das mudas sombreadas. Concluiu-se que mudas do jequitibá-rosa, em sua fase inicial, apresentam bom crescimento quando cultivadas na faixa de 54 % a 64 % de luminosidade.
... Recent studies have pointed out that as Cariniana legalis is classified as a late successional species and is shade tolerant, it is physiologically adapted to shade conditions and therefore, shading is a necessary step to produce its seedlings (REGO andPOSSAMAI, 2011, PORTELA et al., 2017). The best conditions for the growth and development of C. legalis seedlings includes shading at a range of 50% to 30% (REGO and POSSAMAI, 2011). ...
... Recent studies have pointed out that as Cariniana legalis is classified as a late successional species and is shade tolerant, it is physiologically adapted to shade conditions and therefore, shading is a necessary step to produce its seedlings (REGO andPOSSAMAI, 2011, PORTELA et al., 2017). The best conditions for the growth and development of C. legalis seedlings includes shading at a range of 50% to 30% (REGO and POSSAMAI, 2011). In this context this work aimed to define the shading period necessary to produce C. estrellensis seedlings with a high-quality standard. ...
... Firstly, positive phototropism, which is the growth towards a source of electromagnet energy, solar radiation, or others, triggered by a low light intensity environment, promotes a higher plant height, meaning the plant survives for longer in the environment (NERY et al., 2016;TAIZ et al., 2017). Secondly, a milder leaf temperature could lead to the efficient temperature control of the leaf, resulting in a better hydric status and an optimized temperature for photosynthetic activity (REIS et al., 1994;REGO and POSSAMAI, 2011). According to Rego and Possamai (2006), the reduced growth in a full sun environment reflects the intense radiation, leading to stomata closure, decreasing the internal CO2 concentration, and damaging the photosynthetic apparatus. ...
... Under natural conditions, these species would benefit from small clearings in the canopy. In addition, if the growth in height of C. fairchildiana was lower in the sunlight treatment, that is, a more illuminated environment compared to the T75 treatment, it may also be related to the control of the transpiratory process and thermal equilibrium strategies favored in a milder environment (Rego & Possamai, 2006). C. guianensis and I. edulis showed a lower growth in height in the sun-light treatment. ...
... This may be related to an intolerance by these species to an excess of luminosity at the juvenile phase, reducing the photosynthetic use of light and increasing light dissipation. Rego & Possamai (2006) stated that, for some species, the reduction of height growth under natural light is associated with an increased light availability, increases in leaf temperature, intensification of respiratory rate and induction of stomata closure, leading to a reduction of carbon sequestration. This behavior, a lower growth in height when exposed to sunlight, was also reported for several tree species during the juvenile phase (Scalon et al., 2006;Silva et al., 2007;Dutra et al., 2012;Ferreira et al., 2012). ...
... It is important to note that the CCI variable was collected using a portable chlorophyll meter (non-destructive optical method) which expresses chlorophyll index and not an absolute value per unit area or mass, although this type of result is proportional to the concentrations of chlorophyll in leaves (Barbieri Junior et al., 2012). In this sense, Rego & Possamai (2006) observed decreases in the chlorophyll content of Cariniana legalis when exposed to sunlight, as well as Engel & Poggini (1991), studying chlorophyll contents in four tree species submitted to different light treatments. This was observed for C. guianensis in this study, however for CCI values, which agrees with Gonçalves et al. (2012), who verified a decrease in CCI values for Swietenia macrophylla exposed to sunlight. ...
... Este aumento também pode estar associado às maiores taxas de degradação da clorofila a quando comparada às taxas de degradação da clorofila b (Engel & Poggiani, 1991). O aumento dos teores de clorofila nas folhas aumenta a capacidade fotossintética, tal como a luz na faixa do verde, presente em grande quantidade no interior do dossel das florestas (Rego & Possamai, 2006). ...
... Mudas de macacaporanga cultivadas sob 50% e 70% de sombreamento apresentaram maiores quantidades de massa seca foliar (Tabela 4), semelhante ao observado para Virola surinamensis (Lima et al., 2007) e Caesalpinia ferrea (Lenhard et al., 2013). Por outro lado, algumas espécies, como o jequitibá-rosa (Cariniana legalis) e cumaru-de-cheiro (Amburana cearensis), acumulam maior quantidade de biomassa foliar quando cultivadas sob luz plena (Ramos et al., 2004;Rego & Possamai, 2006). ...
Com o objetivo de avaliar as respostas ecofisiológicas de mudas de macacaporanga (Aniba parviflora) em diferentes níveis de sombreamento foi conduzido um experimento no viveiro de mudas da Universidade Federal do Oeste do Pará, em Santarém-PA. Os níveis de sombreamento foram 30%, 50% e 70% de sombreamento e a pleno sol com 0% de sombreamento. O delineamento foi inteiramente casualizado, com quatro repetições, das quais cada uma foi composta por cinco plantas. Foram avaliados altura, diâmetro, número de folhas, área foliar, área foliar específica, massa seca da raiz, caule, folhas e total, taxa assimilatória líquida, condutância estomática, transpiração, eficiência do uso da água e teores de clorofila. Os maiores valores para altura, área foliar e área foliar específica foram obtidos sob 70% de sombreamento, no entanto, para diâmetro e número de folhas os maiores valores foram sob 50% de sombreamento. O sombreamento de 70% proporcionou os maiores valores na taxa assimilatória líquida, condutância estomática, transpiração, eficiência do uso da água, clorofilas a, b e total. O sombreamento de 50% ocasionou os maiores valores na massa seca de raiz, caule, folhas e total. O nível de sombreamento de 50% proporcionou o melhor crescimento e desenvolvimento das mudas.
... Este comportamento pode ser consequência do sombreamento proporcionado pelo ganho em altura das plântulas nesta fase de desenvolvimento. O sombreamento de plantas provoca este comportamento fisiológico (Rego & Possamai, 2006). ...
... Este comportamento pode ser consequência do sombreamento proporcionado pelo ganho em altura das plântulas nesta fase de desenvolvimento. O sombreamento de plantas provoca este comportamento fisiológico (Rego & Possamai, 2006). ...
A produção agroecológica vem aumentando muito nos últimos anos, constatando a necessidade de medidas mais seguras e eficazes no controle de pragas agrícolas por meio do uso de produtos naturais como os óleos essenciais. O presente estudo teve como objetivo avaliar a composição química do óleo essencial das flores de Bauhinia forficata, sua atividade antifúngica, bem como seu efeito na germinação de sementes de Curcubita maxima. O óleo essencial foi extraído por hidrodestilação e analisados por cromatografía gasosa acoplado à espectrômetria de massas (GC-EM). Posteriormente foram avaliados em diferentes concentrações quanto à atividade antifúngica sobre Sclerotinia sclerotiorum, Rhizopus microsporus e Colletotrichum gloeosporioides. No ensaio de desenvolvimento germinativo, as sementes de C. maxima foram imersas em diferentes doses de óleo essencial e comparados sua germinação e desenvolvimentos com fungicida comercial Vitavax thiram®. Os compostos majoritários identificados foram guaia-1(10),11-dieno (66,17%), α-pineno (14,06%) e β-pineno (4,14%). O óleo essencial das flores de B. forficata nas maiores concentrações inibiu o crescimento micelial dos fungos R. Microsporus, C. gloeosporioides e S. Sclerotiorum em 37,71%; 73,7% e 25,74%, respectivamente. O óleo essencial das flores de B. forficata na dose de 30 µL favoreceu a germinação e o desenvolvimento das plântulas sem diferença significativa em relação ao fungicida comercial Vitavax thiram®, o que implica em maior e mais saudável produção. Esses resultados indicam que o óleo essencial de B. forficata apresenta aspectos positivos para produções agroecológicas o que remete a grandes perspectivas evolutivas para o meio sustentável.
... amazonicum e utilizar como substrato uma mistura de solo e adubo (esterco bovino) também não obteve diferenças estatísticas. Contudo, a influência do substrato em diferentes proporções pode alterar quantitativamente o teor de pigmentos fotossintéticos (Afonso et al., 2017), visto que o teor de clorofila nas folhas é de suma importância para aferir o potencial fotossintético das plantas, pelo seu vínculo direto com a absorção e transferência de energia luminosa que interferem no crescimento (Rego & Possamai, 2006 ...
O Cerrado é um bioma do tipo biócoro, que ocupa cerca de 25% do território brasileiro, localizado principalmente na região central. O Schizolobium parahyba var. amazonicum (Huber ex Ducke) Barneby é uma espécie da família Fabaceae, de ocorrência em mata primária e secundária de terra firme da região amazônica. Esse trabalho tem como objetivo avaliar o desenvolvimento da espécie Schizolobium parahyba var. amazonicum diante de diferentes proporções de substrato alternativo. Foram utilizados 4 tratamentos, distribuídos da seguinte maneira, T1- Substrato Preparado (SP) 100% (Terra preta, esterco bovino e palha de arroz), testemunha, T2- 80% SP + 20% Pó de Rocha (PR), T3- 65% SP + 35% PR, T4-50% SP + 50% PR. O delineamento utilizado foi em blocos casualizados, com 5 repetições e os parâmetros utilizados foram: altura, diâmetro, teor de clorofila, massa seca da raiz (MSR), massa seca da parte aérea (MSPA), massa seca total (MST), razão massa seca da raiz e massa seca da parte aérea (MSR/MSPA), e índice de qualidade de Dickson. A análise de variância e as médias foram comparadas pelo teste de Tukey a 5% de probabilidade através do programa Sisvar. Em todas as variáveis analisadas não houve diferença significativa para todos os tratamentos testados. O uso do pó de rocha como fertilizante não apresentou efeitos significativos no desenvolvimento da espécie estudada.
... Authors such as Wiebel et al. (1994) and Rego and Possamai (2006), when analyzing other tree species, noticed low levels of chlorophyll due to greater irradiance. It is noticeable, therefore, that the species in question is susceptible to photo-oxidation. ...
The aim of the present study was to determine and compare chlorophyll concentrations in adult individuals of Tectona grandis in two plantations in the municipality of Irituia-PA. A completely randomized design was used, with two treatments (T1 = planting without fertilization and T2 = planting with fertilization) where 50 adults individuals of T. grandis were randomly chosen, being 25 trees per planting area. After collection, the chlorophyll content was obtained from 10 different points on the leaf using an atLEAF+ chlorophyll meter, in addition to measuring climatic data of temperature and humidity.
Finally, the chlorophyll contents of generic units generated by the
equipment were converted to mg/cm2. The highest measured chlorophyll
contents were attributed to the T2 area, which receives constant
fertilization, proving the existence of the relationship between the
pigment and the disposition of nutrients in the soil. Regarding the levels
of chlorophyll by leaf measurement points, the values corresponding to
points 1, 2, 3 and 4 were statistically higher than the others, showing
that there is greater pigment production in the lower part of the leaf
blade. As for the measurement times, a relationship was directly
proportional to the chlorophyll contents, in conjunction with
temperature. Therefore, based on the rise of chlorophyll levels, there was
no photo-oxidation of the pigments during the observed period.
... There were no statistical differences in the chlorophyll content of the varieties studied for Chlorophill A and B. The determination of the chlorophyll content in the leaves is important to estimate the photosynthetic potential of the plants by their direct connection with the absorption and transfer of light energy that will reflect in the growth (Rego & Possamai, 2006). ...
... O sombreamento artificial realizado através do uso de telas do tipo sombrite é um recurso muito utilizado no estudo das necessidades luminosas das diferentes espécies em condições de viveiro (Rêgo e Possamai, 2006). Kefer et al., (2019) (Saraiva, 2013). ...
... Therefore, the light energy absorbed by the leaves can only be transferred to the biochemical stage of photosynthesis through processes mediated by chlorophylls. The levels of chlorophylls and carotenoids in the leaves are used to estimate the photosynthetic potential of plants, due to their direct connection to the absorption and transfer of light energy and, consequently, with their acclimatization and growth in different environments [2]. ...
In recent years, marine organisms have received attention for being a source of natural compounds, enabling the creation of a new and
promising field of study. Marine macroalgae are a vast source of raw materials and biologically active molecules used in the pharmaceutical,
cosmetic, food and agricultural industries. Due to its importance, the present study aimed to assess whether the bioextract of the red macroalgae
Kappaphycus alvarezii acts as a biostimulant in the metabolism of plants and changes the reflectance indexes. In particular, the biological activity
of the red macroalgae bioextract was focused on stimulating plant growth and photosynthetic activity. A scientific experiment was carried out
using a red marine macroalgae bioextract applied on the pepper culture (Capsicum annuum L.). The pepper culture was chosen due to its high
sensitivity to stress, generating good responses in the evaluation of the biostimulant and anti-stress capacity of an algal bioextract. The fresh
mass of the aerial part and the length of the aerial part were evaluated, and a metabolic evaluation was also performed, represented by the
photosynthetic rate produced by the pepper plants.
Kewords: Seaweed; Kappaphycus alvarezii; Chlorophyll a and b; Biostimulant; Capsicum annuum
... It generates micrometeorological changes that alter environmentplant relationships (REGO; POSSAMAI, 2006;SHAHAK, 2008). The use of colored shade nets at sites subject to high temperatures and light intensity reduces the amount of radiant energy, which positively affects physiological processes in most plants (ARAÚJO et al., 2006;HENRIQUE et al., 2011). ...
Watermelon (Citrullus lanatus) belongs to the plant family Cucurbitaceae. It is cultivated in many regions of Brazil, particularly in rainfed areas; thus, it is subject to the problems arising from irregular rainfall. Hydrogel is a soil conditioner used to retain and provide water to plants for long periods of time. Therefore, incorporating hydrogel into the soil should increase water availability for watermelon cultivation, and may be an alternative method to reduce the risk of water deficit. This study evaluated the effect of different concentrations of hydrogel on the initial growth of watermelon cv. 'Crimson Sweet' under different shading conditions. The experiment was carried out in a greenhouse with completely randomized design with a 4×3 factorial scheme. The treatments consisted of four hydrogel doses (0.0; 1.5; 3.0; and 6.0 g L-1 substrate), three shading conditions (under full sun; black shade net, and red shade net, both with 50% shading), and five replicates per treatment. The variables evaluated were plant height; stem diameter; shoot, root, and total dry matter; and leaf area. The best hydrogel dose for watermelon cultivation was 1.5 g L-1, but the higher doses impaired plant growth, regardless of shading conditions. The black net improved biomass accumulation in 'Crimson Sweet' watermelon, whereas the red net induced plant etiolation.
... A rúcula (Eruca sativa) é uma hortaliça que se destaca por suas variadas propriedades nutricionais, sendo consumida mundialmente (MAIA, 2006). O sucesso na produção de mudas de hortaliças depende de resultados satisfatórios nos canteiros finais de produção (CARMELLO, 1995). ...
... A rúcula (Eruca sativa) é uma hortaliça que se destaca por suas variadas propriedades nutricionais, sendo consumida mundialmente (MAIA, 2006). O sucesso na produção de mudas de hortaliças depende de resultados satisfatórios nos canteiros finais de produção (CARMELLO, 1995). ...
... A rúcula (Eruca sativa) é uma hortaliça que se destaca por suas variadas propriedades nutricionais, sendo consumida mundialmente (MAIA, 2006). O sucesso na produção de mudas de hortaliças depende de resultados satisfatórios nos canteiros finais de produção (CARMELLO, 1995). ...
... In order to evaluate the effect of NADPH on the reaction time (Pimentel, 1998;Taiz and Zeiger, 2006). The chlorophyll and carotenoid contents in the leaves are used to estimate the photosynthetic potential of the plants, within their direct connection with the absorption and transfer of light energy besides growth and adaptation to different environments (Rego and Possamai, 2006). In this perspective, the objective of this work was to determine the levels of vitamin C and nitrate in the three lettuce cultivars in a hydroponic system using wastewater and well-water conditions. ...
The objective of this work was to determine the levels of vitamin C, nitrate and chlorophyll in three lettuce cultivars in a hydroponic system using waste- and well-water. The experiment was conducted in a hydroponic system using laminar flow technique and nutrients in a protected environment. The experimental design was randomized blocks with treatments set up in split-plots with three replications, whose main plots devoted to lettuce cultivars and sub-plots to hydroponic solutions. The experimental solutions consisted of 7 nutrients (S): S1=Furlani solution, S2=domestic wastewater, S3=optimized domestic wastewater, S4 =well water S5 =optimized well water; S6 = reactor wastewater solution and S7 =optimized reactor wastewater solution and the subplot for the three cultivars of iceberg lettuce (Verônica, Vanda, and Thais). The following variables were determined: nitrate, vitamin C and chlorophyll content using the method described by Lichtenthaler. The results indicated that highest content of vitamin C was found in the Vanda cultivar using the S1 solution. For Veronica cultivar, the highest levels of vitamin C were observed at solutions S1, S2, S3, S4, and S7. The solutions S2 and S3 did not differ from one another in all three cultivars. For the Vanda cultivar, solutions S1, S4 and S7 were the ones that promoted the highest levels of nitrate, 4.61; 3, 32 and 2.64 g kg-1, respectively. Evaluating the effect of the solution within the cultivars, we verified that the highest nitrate values obtained from S2 nutrition for cultivars Thais and Verônica. Regarding the S5 solution, the Verônica cultivar presented the highest concentration of this nutrient. The cultivate Thaís, the highest contents of chlorophyll b were found in solutions S7, S6, S4, S3 and S2, where they did not differ significantly. Regarding to Vanda cultivar the highest values of chlorophyll b were present in solutions S2 and S5. The Verônica cultivar independent of the solution used presented the same values of this pigment.
... One of these differences is the amount of layers and distribution of mesophyll cells (Yano and Terashima, 2004). There may also be variations in the concentration of photosynthetic pigments (Rego and Possamai, 2006) and maintenance and protection of the photosynthesis process (Silva et al., 2010). Thus, due to the architecture of the canopy, the morphophysiological responses of the leaves to light vary according to the different light conditions. ...
This work was carried out to verify the plasticity of saplings of Cabralea canjerana plants and their capacity to adapt to different light environments by means of morphological and physiological characteristics. For this, 12 plants of a secondary Deciduous Seasonal Forest fragment were selected, six growing under canopy and six in full sun. Trees were classified according to their sociological position as emergent and dominated. The leaves were classified as apical, intermediate and basal according to their position in the canopy. The variables measured were: total number of leaves, width, length, thickness, leaf area and dry mass of leaflets; content of chlorophyll a and b and carotenoids. Emergent leaflets of the upper position of the canopy in full sun, which are considered the most exposed to luminosity, presented xeromorphic characteristics such as leaflet size reduction, greater limbus thickness, smaller leaf area and lower content of chlorophyll b. The similarity in the dry mass and pigment content demonstrates that the photosynthetic activity of the C. canjerana plants analyzed is not being affected by the different conditions of the environment, which demonstrates the plasticity of the species and its capacity of development in several light conditions.
... (Fabaceae), Alvarenga et al. (2003) estudaram o efeito de quatro níveis de sombreamento sobre a concentração de clorofila em Croton urucurana Baill. (Euphorbiaceae), Scalon et al. (2003) avaliaram o crescimento inicial de mudas de Bombacopsis glabra (Pasq.) A. Robyns (Malvaceae) em condição de sombreamento, Rego & Possamai (2006) avaliaram o efeito do sombreamento sobre o teor de clorofila e crescimento inicial de Jequitibá-rosa, Dousseau et al. (2007) analisaram a influência de condições de sombreamento sobre o crescimento de Tapirira guianensis Aulb. (Anacardiaceae), Martinazzo et al. (2007) avaliaram o efeito do sombreamento sobre o crescimento inicial e teor de clorofila em Eugenia uniflora L. (Myrtaceae), Magalhães et al. (2009) avaliaram a aclimatação de mudas de acariquara à alta irradiância, Favaretto et al. (2011) estudaram as respostas das enzimas antioxidantes de espécies arbóreas sob condição de sol e sombra, Furlan (2013) avaliou o teor de pigmentos em Theoboma cacao L. (Sterculiaceae) em condições de radiação solar, Mokochinski et al. (2014) avaliaram a variação estacional do teor de clorofila em Inga marginata Willd. ...
... Light quantity and quality appear to be key factors for the development of this species, as C. legalis is considered a late secondary growth species, presenting sensitivity to high light intensity and direct incidence, especially in the early stages of development (Rego and Possamai 2006;Vieira et al. 2012). These characteristics of C. legalis emphasize the need to understand the effect of this environmental factor on its in vitro development. ...
The effect of different light sources on in vitro shoot development in Cariniana legalis, an endangered species from the Atlantic Forest, was evaluated. Cotyledonary and apical nodal explants were subjected to light-emitting diode (LED) lamps with different spectral combinations and fluorescent lamps (control). Shoot growth, endogenous contents of free polyamines (PAs) and proteomic profiles were analyzed at 60 days of development. Treatments consisting of white, low-blue and deep-red, with (W/lB/dR/fR) and without (W/lB/dR) far-red spectra, resulted in greater elongation of shoots from cotyledonary nodal explants, and the low-blue and deep-red spectral combination appeared to be a positive factor stimulating shade-avoidance responses. Shoots grown under the W/lB/dR LED exhibited greater elongation and higher contents of free putrescine, spermidine and total free PAs compared to those grown under the fluorescent lamp. Comparative proteomic analysis revealed 15 up- and 41 down-regulated proteins in shoots grown under the W/lB/dR LED lamp when compared to the control. The differentially up-regulated proteins in shoots grown under the LED lamp are related to cell organization and composition, as well as biological regulation processes, whereas proteins related to stress processes were down-regulated. The LED lamp consisting of white, low-blue and deep-red spectra increased shoot elongation in C. legalis, in association with differential accumulation of proteins and PAs, suggesting the relevance of source light on in vitro shoot development in this species.
... A altura de planta e um dos parâmetros mais utilizados para avaliar a respostas de crescimento de plantas submetidas a diferentes intensidades luminosa, sabido que a capacidade em crescer rapidamente quando sombreadas pode ser um mecanismo de adaptação, caracterizando assim uma valiosa estratégia para escapar do sombreamento (REGO; POSSAMAI, 2006). Os resultados apresentados neste trabalho para altura, mostram que as plantas de Jacaranda brasiliana submetidas ao tratamento de 50% de sombreamento obteve os melhores resultados, indicando que está espécie investe mais em altura em ambientes com luminosidade intermediária, como clareiras. ...
Devido à devastação de áreas do cerrado, espécies nativas encontram-se ameaçadas de extinção. Nesse sentido, estudos sobre o requerimento de luz nos estágios iniciais de espécies arbóreas tornam-se necessários. O presente trabalho teve como objetivo avaliar o desenvolvimento inicial de mudas de Jacaranda brasilianaem diferentes níveis de sombreamento. O experimento foi conduzido em delineamento em blocos casualizados, com três níveis de bombreamento e 15 repetições. Ao final dos 50 dias após a emergência, as mudas foram submetidas aos níveis de sombreamento: pleno sol, 50% de sombreamento artificial e sombra natural, no qual as plantas foram colocadas em uma área remanescente de cerrado nativo. Os dados foram avaliados em intervalo de 21 dias, aos 60, 82, 103, 124 e 145 dias após emergência. Aos 145 dias as mudas submetidas ao crescimento a pleno sol apresentaram resultados promissores para o diâmetro (7,61 mm), massa seca das folhas (10,75 g), massa seca do caule (24,62 g), massa seca da raiz (12,38 g), massa seca total (47,75 g), relação parte aérea/raiz (2,86 g) e índice de qualidade de Dickson (6,75) sendo esta condição a mais recomendada para produção de mudas em larga escala a custo zero. Para a condição de sombra natural os resultados apresentaram-se inferiores em comparação aos tratamentos pleno sol e 50% de sombreamento.
Palavras-chave: Jacaranda brasiliana, áreas degradadas, luminosidade.
Initial development of caroba plastics under shading influence
ABSTRACT: Due to the devastation of cerrado areas, native species are hreatened with extinction. In this sense, studies on the light requirement in the early stages of tree species become necessary. The present work had as objective to evaluate the initial development of Jacaranda brasilianaseedlings at different levels of shading. The experiment was conducted in a randomized complete block design with three levels of shading and 15 replicates.
At the end of the 50 days after emergence, the seedlings were submitted to shade levels: full sun, 50% artificial shading and natural shade (under trees in a native cerrado). Data were evaluated at 21 days interval at 60, 82, 103, 124 and 145 days after emergence. At 145 days the seedlings submitted to full sun rowth presented promising results for the diameter (7.61 mm), leaf dry mass (10.75 g), stem dry mass (24.62 g), root dry mass (12.38 g), total dry matter (47.75 g), erial part / root ratio (2.86 g) and Dickson quality index (6.75) being the most ecommended condition for seedling production in Large scale at zero cost. For the natural shade condition the results were lower compared to full sun treatments and 50% shading.
Keywords: Jacaranda brasiliana, degraded areas, luminosity.
... For RCI, chlorophyll a, b and total chlorophyll, no difference was noted among the treatments, demonstrating that these characteristics were not affected by shade net color (Table 1). Gonçalves et al., (2012) and Rego and Possamai (2006) report a strong correlation between the increase in chlorophyll content and lower intensity of radiation in mahogany and jequitibá-rosa, respectively. However, Sabino et al. (2016) and Henrique et al. (2011) analyzed ipe and coffee seedlings grown under colored shade nets, respectively, and found results that corroborate those found in this study. ...
Butia capitata (Mart.) Becc., commonly known as jelly palm, is a palm tree native to the Cerrado biome. It is considered an endangered species owing to intensive extractive exploitation of its fruits, with slow and uneven seminiferous propagation as an aggravating factor. Thereby, there are some bottlenecks related to jelly palm seedling production that needs to be optimized. Light quality and intensity is very important to seedling production, as it controls the metabolism of plants and consequently their growth and development. Thus, the aim of this work is to evaluate the effect of shade nets on the growth and physiological aspects of jelly palm seedlings. The experimental design was completely randomized, with five treatments, ten replicates and eight plants per replicate, totaling 400 plants. Experimental treatments consisted of the use of shade nets with 50% shading and different radiation intensity: white (985 µmol m-2 s-1), red (327 µmol m-2 s-1), black (433 µmol m-2 s-1), and silver (405 µmol m-2 s-1). Full sun (1000 µmol m-2 s-1) was used as the control treatment. Growth and physiological analyses of the plants were performed after six months of treatment. We concluded that the red shade net increases growth and biomass of Butia capitata plants. However, the use of shade nets had no effect on the tested physiological characteristics of this species. The red shade net is the most suitable for the production of Butia capitata seedlings in the southern region conditions of Minas Gerais State.
... A altura de planta e um dos parâmetros mais utilizados para avaliar a respostas de crescimento de plantas submetidas a diferentes intensidades luminosa, sabido que a capacidade em crescer rapidamente quando sombreadas pode ser um mecanismo de adaptação, caracterizando assim uma valiosa estratégia para escapar do sombreamento (REGO; POSSAMAI, 2006). Os resultados apresentados neste trabalho para altura, mostram que as plantas de Jacaranda brasiliana submetidas ao tratamento de 50% de sombreamento obteve os melhores resultados, indicando que está espécie investe mais em altura em ambientes com luminosidade intermediária, como clareiras. ...
RESUMO: Devido à devastação de áreas do cerrado, espécies nativas encontram-se ameaçadas de extinção. Nesse sentido, estudos sobre o requerimento de luz nos estágios iniciais de espécies arbóreas tornam-se necessários. O presente trabalho teve como objetivo avaliar o desenvolvimento inicial de mudas de Jacaranda brasiliana em diferentes níveis de sombreamento. O experimento foi conduzido em delineamento em blocos casualizados, com três níveis de sombreamento e 15 repetições. Ao final dos 50 dias após a emergência, as mudas foram submetidas aos níveis de sombreamento: pleno sol, 50% de sombreamento artificial e sombra natural, no qual as plantas foram colocadas em uma área remanescente de cerrado nativo. Os dados foram avaliados em intervalo de 21 dias, aos 60, 82, 103, 124 e 145 dias após emergência. Aos 145 dias as mudas submetidas ao crescimento a pleno sol apresentaram resultados promissores para o diâmetro (7,61 mm), massa seca das folhas (10,75 g), massa seca do caule (24,62 g), massa seca da raiz (12,38 g), massa seca total (47,75 g), relação parte aérea/raiz (2,86 g) e índice de qualidade de Dickson (6,75) sendo esta condição a mais recomendada para produção de mudas em larga escala a custo zero. Para a condição de sombra natural os resultados apresentaram-se inferiores em comparação aos tratamentos pleno sol e 50% de sombreamento. Palavras-chave: Jacaranda brasiliana, áreas degradadas, luminosidade. ABSTRACT: Due to the devastation of cerrado areas, native species are threatened with extinction. In this sense, studies on the light requirement in the early stages of tree species become necessary. The present work had as objective to evaluate the initial development of Jacaranda brasiliana seedlings at different levels of shading. The experiment was conducted in a randomized complete block design with three levels of shading and 15 replicates. At the end of the 50 days after emergence, the seedlings were submitted to shade levels: full sun, 50% artificial shading and natural shade (under trees in a native cerrado). Data were evaluated at 21 days interval at 60, 82, 103, 124 and 145 days after emergence. At 145 days the seedlings submitted to full sun growth presented promising results for the diameter (7.61 mm), leaf dry mass (10.75 g), stem dry mass (24.62 g), root dry mass (12.38 g), total dry matter (47.75 g), aerial part / root ratio (2.86 g) and Dickson quality index (6.75) being the most recommended condition for seedling production in Large scale at zero cost. For the natural shade condition the results were lower compared to full sun treatments and 50% shading.
... The behavior of Apuleia leiocarpa in the south region of Brazil demonstrated to be similar to which was found in other studies, such as Rêgo and Possamai (2006); when evaluating light (full sun, 34, 44, 64 and 70 %) in Cariniana legalis Cariniana legalis Kuntze (jequitibá-rosa), they observed that the contents of chlorophyll a, b and total were higher in plants under lower light condition. Lima et al. (2010) confirmed that the highest carotenoid content in Hymenaea courbaril L. (jatoba) and Enterolobium contortisiliquum (Vell.) ...
This study aimed at identifying the most appropriate level of shading for initial growth of Apuleia leiocarpa seedlings, through their survival, morphological and physiological/biochemical parameters. The following treatments were evaluated: 0 (full sun), 18, 50 and 70 % of shading. Survival was assessed at 30 and 360 days after planting and morphological parameters such as height (H), stem diameter (SD) and H/SD ratio were measured bimonthly for a year. Physiological parameters as contents of chlorophyll a, chlorophyll b, chlorophyll a/b ratio, carotenoids, lipid peroxidation, acid phosphatase enzyme activity, initial fluorescence, maximum fluorescence, maximum quantum yield of photosystem II and electron transport rate were estimated at 180 and 360 days after planting. At 30 days after planting (d.a.p) there was no mortality of Apuleia leiocarpa seedlings influence of different levels of shading. In the assessments performed at 180 and 360 d.a.p., there was no significant difference among levels of shading for H and SD. However, high mortality rates were observed at 360 d.a.p., especially in full sun. Morphological and physiological parameters of Apuleia leiocarpa plants showed this species requires shading (18 and 50 %) in their early stages of growth.
... Such an environmental compound, the light interferes on plant growth because provide energy to photosynthesis and signals, which regulates the plant development by sensitive light receptors in different intensity, spectral quality and state of polarization (Rego & Possamai, 2006). In addition, different light spectrums can increase the proportion of active forms in terms of phytochromes triggering answers in plant development (Victório & Lage, 2009). ...
For each vegetable species, there is a specific environment conditions to occur the seed germination process. However, there is a little information regarding the necessary conditions for Niger (Guizotia abyssinica (L.f.) Cass.) seeds germination. The aim of this research was to evaluate the influence of different temperatures and types of light on Niger (Guizotia abyssinica (L.f.) Cass.) seeds germination. Seeds were sown on two sheets of "germitest" paper inside plastic box type "gerbox" and placed on B.O.D. Treatments were constituted of two constant temperatures (15°C and 25 °C, respectively) and an alternating temperature (20-30 °C) under 10 hours for the lowest temperature and 14 hours for the highest temperature and they were associated to the wavelengths as follows: blue (440 nm), green (560 nm), red (660 nm), extreme red (730 nm), white light and dark. The experiment was conducted in a completely randomized design with four replicates of 50 seeds. Effects of different temperatures and qualities of light were evaluated by seeds germination and vigor. Higher germination of Niger seeds is observed in temperatures of 25 and 20-30 °C and they can be considered as non-photoblastic.
... The lowest chlorophyll a content was observed in the plants of the pre-commercial line, UFU-222. According to Rego and Possamai (2011), the chlorophyll content, in a plant, varies in function of climatic conditions and an increase in this pigment reflects in an increase in the photosynthetic rate. ...
Water stress can affect the yield in tomato crops and, despite this, there are few types of research aiming to select tomato genotypes resistant to the water stress using physiological parameters. This experiment aimed to study the variables that are related to the gas exchanges and the efficiency in water use, in the selection of tomato genotypes tolerant to water stress. It was done in a greenhouse, measuring 7 x 21 m, in a randomized complete block design, with four replications (blocks), being five genotypes in the F2BC1 generation, which were previously obtained from an interspecific cross between Solanum pennellii versus S. lycopersicum and three check treatments, two susceptible [UFU-22 (pre-commercial line) and cultivar Santa Clara] and one resistant (S. pennellii). At the beginning of flowering, the plants were submitted to a water stress condition, through irrigation suspension. After that CO2 assimilation, internal CO2, stomatal conductance, transpiration, leaf temperature, instantaneous water use efficiency, intrinsic efficiency of water use, instantaneous carboxylation efficiency, chlorophyll a and b, and the potential leaf water (Ψf) were observed. Almost all variables that were analyzed, except CO2 assimilation and instantaneous carboxylation efficiency, demonstrated the superiority of the wild accession, S. pennellii, concerning the susceptible check treatments. The high photosynthetic rate and the low stomatal conductance and transpiration, presented by the UFU22/ F2BC1#2 population, allowed a better water use efficiency. Because of that, these physiological characteristics are promising in the selection of tomato genotypes tolerant to water stress.
... As folhas configuram um dossel que absorve luz e influencia diretamente nas taxas fotossintéticas e no crescimento e, por isso, as plantas apresentam variações na sua capacidade de responder à disponibilidade de luz (TAIZ; ZEIGER, 2004). Um método utilizado para o estudo das necessidades luminosas é o sombreamento artificial, visto que este isola e quantifica o efeito da intensidade luminosa e fornece às parcelas experimentais condições uniformes de iluminação, quando comparada aos estudos em condições naturais (REGO; POSSAMAI, 2006). ...
There may be differences in the physiological, biochemical, anatomical and growth of a plant when it is subjected to changes in light levels to which it is adapted. The plant response to different light levels is important in determining their growth potential and occurrence, and also evaluate their competitiveness in different environmental conditions. The objective of this study was to evaluate the characteristics of radish plants to different levels of brightness. The experiment was conducted in a greenhouse and the experimental design was randomized blocks with seven replicates. The treatments consisted of four solar radiation intensities (100%, 70%, 50% and 30% Brightness). The reduction in light intensity to 70%, 50% and 30% was obtained with the use of halftone screens 30%, 50% and 70%, respectively. They evaluated the contents of chlorophyll a, b and total, number of leaves, leaf area, fresh weight and dry shoot and root system. It is concluded that the shading has not affected the number of leaves and leaf area; 50% shading decreased the chlorophyll content; shading levels of 30%, 50% and 70% promoted the reduction in the mass of tuberous roots.
Podem ocorrer diferenças nas características fisiológicas, bioquímicas, anatômicas e de crescimento de uma planta quando esta for submetida a modificações nos níveis de luminosidade ao qual está adaptada. A resposta da planta às diferentes condições de intensidade luminosa é importante para determinar o seu potencial de crescimento e ocorrência e, também, avaliar a sua capacidade competitiva em diferentes condições ambientais. O objetivo deste trabalho foi avaliar as características de plantas de rabanete submetidas a diferentes níveis de luminosidade. O experimento foi conduzido em casa de vegetação e o delineamento experimental utilizado foi de blocos ao acaso com sete repetições. Os tratamentos foram compostos por quatro intensidades de radiação solar (100%, 70%, 50% e 30% de luminosidade). A redução de intensidade de luz para 70%, 50% e 30% foi obtida com o uso de telas de sombreamento de 30%, 50% e 70%, respectivamente. Foram avaliados os teores de clorofila a, b e total, número de folhas, área foliar, massa da matéria fresca e seca da parte aérea e sistema radicular. Conclui-se que o sombreamento não afetou o número de folhas e a área foliar; 50% de sombreamento promoveu redução no teor de clorofila; os níveis de sombreamento de 30%, 50% e 70% promoveram a redução na massa das raízes tuberosas.
... These results denote the photosynthetic similarity of the plants under three types of soil, showing that the chemical and physical properties specific to each soil such as texture, structure, porosity, pH and nutrient availability, were not sufficient to interfere with the assimilate production and, consequently, alter plant growth. The total amount of the plant dry matter accumulation is direct reflection of the net photosynthetic production, plus the amount of absorbed mineral nutrients (REGO; POSSAMAI, 2006). Thus, the juazeiro plants have high growth potential in different edaphic environments, which indicate a long adaptation process of this species to the limitations inherent in their natural habitat. ...
Considering the potential and importance of biodiversity of the Caatinga biome, studies on endemic species are relevant to conservation of its natural resources. The objectives of this work was to evaluate seed viability and physical methods for overcoming seed dormancy in juazeiro (Ziziphus joazeiro Mart.) and assess the influence of different types of soil on the initial growth of juazeiro plants. The experiments were conducted in three stages. In the first stage, the viability of seeds from different lots was evaluated using the tetrazolium test. The second stage was conducted in a plant nursery, evaluating the application of physical processes (scarification with sandpaper and hammer) in overcoming seed dormancy, and the initial growth of the plants. In the third step, the chlorophyll a and b contents, gas exchange and dry matter accumulation were evaluated in young juazeiro plants in three types of soil (Oxisol, Entisol and Vertisol). The results indicate that the viability of juazeiro seeds is greatly influenced by differences between the progenitor plants and by storage conditions, which enable a longevity of two years when stored at 22°C and 16% of relative humidity. The scarification methods with sandpaper and hammer are not efficient to reduce the time and uniform seed germination. The juazeiro plants have high growth potential in different edaphic environments, adapting well to soils of different textures and chemical compositions. © 2016, Universidade Federal Rural do Semi-Arid. All Rights Reserved.
The objective of this work was to evaluate the influence of shade level on the production of T. myrmecophila seedlings. After 30 days of seedling transplantation, the seedlings were submitted to the following treatments: 100% light (full sun), 75% light and 50% light. The statistical design was completely randomized with 5 replicates of 10 seedlings each per treatment. The data were analyzed by repeated measures in time, in 5 measurements, performed every 30 days (150 days of evaluation). The analyzed variables were shoot height and diameter. The environment with 75% luminosity was the one that contributed most to the growth in height of the seedlings, having presented higher mean values over time, in the 5th month (34.94 cm). The most pronounced effect for growth in diameter was verified in the 5th month of evaluation, where the highest average was obtained in the environment with 50% of shading (4.61 mm). The T. myrmecophila seedlings were influenced by the shading levels used. From the results evaluated, treatments with 75% and 50% of solar radiation provided superior growth for dendrometric variables height and diameter, respectively. Therefore, we recommend environments with 75% and 50% of solar radiation for the production of T. Myrmecophila seedlings.
Paricá (Schizolobium parahyba variety amazonicum) is an important species for reforestation programs in the Amazon; nevertheless, the anatomical and physiological parameters of the seedlings of this species under shading are not yet fully understood. This study evaluated the chlorophyll and carotenoid contents, the stomatal structure, and the stomatal position in the leaf epidermis under shading of paricá seedlings. The experiment comprised a randomized block design in a subdivided plot scheme, with two sources (Belterra and Urupá) and different shading levels (full sun, 30%, 50%, and 70%). At 100 days after sowing, we performed the analyses of photosynthetic pigment concentration and leaf anatomy. We found that the leaf is hypoestomatic with paracitic stomata and unicellular filiform trichomes on both sides. Higher levels of shading increased the contents of chlorophyll a and b and reduced the stomata density and carotenoid contents in the leaves of young paricá, showing that paricá has phenotypic plasticity to shading.
The light directly affects the phytosanitary processes of plants, variations in plant length conditions and conditions directly affecting the production of environmental conditions and variations as well as pigments. In this study, this study aims to evaluate the changes that occur in the gas exchange process and in the production of metabolites in Talisia esculenta seedlings, through the use of colored shading screens. The seeds of T. esculenta were used, which were used in an alternative way, which were sown replacement in substrate (vermiculite: polypropylene), molded to the following treatments in the blue mesh, which were replaced by black and white treatments, which constituted the following treatments. The design was completely randomized with three of six seeds each, totaling eighteen seeds for treatment. After 180 days, plants already defined, the levels of pigments and phenolic compounds were defined. The results of increased energy and protection of wave modulation settings by secondary shadow networks of energy reserves and photoinhibition protection from secondary photoinhibition. Plants are white Talisia esculenta, similar to more identical interpretation shading, such as starch grains and also higher chlorophyll contents. The construction mesh provides the best development of Talisia esculenta (A. St. Hil) Radlk plants.
Esta obra constituiu-se a partir de um processo colaborativo entre professores, estudantes e pesquisadores que se destacaram e qualificaram as discussões neste espaço formativo. Resulta, também, de movimentos interinstitucionais e de ações de incentivo à pesquisa que congregam pesquisadores das mais diversas áreas do conhecimento e de diferentes Instituições de Educação Superiores públicas e privadas de abrangência nacional e internacional. Tem como objetivo reunir experiências técnicas e cientificas de aspectos dendrológicos e ecológicos da vegetação do ecossistema Amazônico. A obra surge na perspectiva de divulgar informações sobre a identificação botânica, dendrológica, composição florística, distribuição e ocorrência e interações das espécies nativas em diferentes ambientes existentes na região. Agradecemos aos autores pelo empenho, disponibilidade e dedicação para o desenvolvimento e conclusão dessa obra. Esperamos também que esta obra sirva de instrumento didático-pedagógico para estudantes, professores dos diversos níveis de ensino em seus trabalhos e demais interessados pela temática.
O objetivo deste trabalho foi avaliar a plasticidade morfoanatômica de plantas de Hippeastrum stylosum Herb. em diferentes condições de luz. Para avaliar os efeitos da exposição prolongada à luz, plantas com cinco folhas completamente expandidas foram colocadas em ambientes com 50%, 75% e 100% (pleno sol) de radiação fotossinteticamente ativa (RFA), obtidos por meio de tela de sombreamento, e mantidas nessas condições durante 60 dias. Em vista frontal, as células epidérmicas são retangulares e organizadas em fileiras. A planta é anfiestomática, estômatos diacíticos, localizados no mesmo nível das células epidérmicas. Há poucos estômatos na face adaxial e muitos na face abaxial da folha. Há muitos estômatos geminados na face abaxial de todos os tratamentos, sendo que na face adaxial esses estômatos foram encontrados somente nas plantas cultivadas com 50% de luminosidade. Cutícula bastante estriada nas plantas cultivadas em local totalmente ensolarado, com 70% de luz apresentaram poucas estriações e lisa com 50% de luz. A cutícula é muito espessa nas plantas cultivadas em local totalmente ensolarado e com 70% de luz, e delgada nas plantas cultivadas com 50% de luz. O mesofilo das folhas é simétrico, o parênquima clorofiliano é internamente envolvido por uma ou duas camadas de células parenquimáticas que delimitam grandes lacunas, que são interrompidas pelas colunas de células parenquimáticas e por pequenos feixes vasculares colaterais que comunicam as faces adaxial e abaxial. As lacunas ocupam aproximadamente 2/3 da espessura foliar. Não houve diferença em relação a essas variáveis nos tratamentos testados.
In tropical forests, different physiological characteristics of leaves in tree species are evidenced by variations in different incident light conditions. We aim to evaluate gas exchange and organization of leaf vascular system in Guazuma ulmifolia Lam. seedlings under different light conditions. Seedlings were obtained from seeds germinated under greenhouse conditions with controlled environment. Ninety days after germination, seedlings in 8kg pots were transferred to the experimental site to allow acclimatization under sun and shade conditions. The experimental design was completely randomized, with two treatments: full sunlight and artificial shading, limiting the luminosity to about 5% of irradiance. Seedlings were maintained under these conditions for 120 days before measuring gas exchange parameters. We measured photosynthetic rate, stomatal conductance, sub-stomatic CO2 concentration, transpiration, and chlorophyll content. Anatomical analysis measured distance between veins, distance from veins to abaxial epidermis, distance from veins to adaxial epidermis, distance from veins to stomata, total leaf thickness, abaxial epidermis thickness, adaxial epidermis thickness, palisade parenchyma thickness, and spongy parenchyma thickness of foliar gas exchange of G. ulmifolia which presented significant differences between light environments. Photosynthetic rate and stomatal conductance were reduced by 78% and 39%, respectively, in shade, while stomatal conductance increased by 31% in full sunlight. Transpiration showed no significant difference between the two treatments, but chlorophyll content was 30% lower in full sunlight. Distance between veins and distance from veins to stomata showed no difference between treatments, but the other parameters increased in full sunlight. Thus, the results showed that the pioneer species G. ulmifolia presented leaf gas exchange acclimated to environments with high luminosity.
El crecimiento compensatorio y las defensas vegetales son respuestas para lidiar con la herbivoría y la luz. El estudio de la influencia de los componentes morfo-fisiológicos, de la asignación de biomasa y de la defensa vegetal podría arrojar información que ayude a entender estas respuestas. Se evaluaron los efectos de la herbivoría y la apertura de claros sobre el crecimiento, los componentes morfo-fisiológicos, la asignación de biomasa y las defensas químicas y físicas en plántulas de Brosimum alicastrum en una selva mediana subcaducifolia. Se utilizó un diseño anidado con sitios de sotobosque y claros (n = 3 en cada uno) y dentro de ellos plántulas sometidas a tres tratamientos de herbivoría: control (n = 10), simulada (n = 10) y natural (n = 10). Se registró a lo largo de seis meses la influencia de la herbivoría sobre el crecimiento (biomasa, área foliar, altura, diámetro y producción de hojas), la producción de fenoles y la dureza foliar. Se halló un crecimiento compensatorio (todas las variables de crecimiento) con la herbivoría natural, subcompensatorio (biomasa, altura y diámetro) con la simulada, y sobrecompensatorio (producción de hojas) con la herbivoría natural sólo en claros. Los componentes morfológicos como el cociente del área foliar (LAR) y el área foliar específica (SLA) fueron mayores bajo claros y el fisiológico, como la tasa de asimilación neta (NAR), en sotobosque. La proporción de biomasa en sotobosque fue mayor hacia hojas y tallos y en claros más alta hacia raíces. La herbivoría fue mayor en claros y los fenoles foliares en sotobosque. No se encontró una relación (compromiso) entre las defensas y el crecimiento, sólo una tendencia negativa con los fenoles bajo condiciones limitantes de recursos, como ocurre en el sotobosque.
A Mata Atlântica é um bioma constantemente ameaçado por perturbações antrópicas. A supressão da vegetação por obras rodoviárias ressalta a necessidade de projetos de conservação das espécies que nela ocorrem. O sucesso do resgate e realocação de plantas, como a palmeira Syagrus romanzoffiana pode contribuir para a conservação dessas espécies. O objetivo deste trabalho foi estudar o crescimento de mudas de S. romanzoffiana resgatadas de áreas de supressão da obra do Rodoanel Mário Covas - Trecho Norte e transplantadas em áreas naturais do Parque Estadual da Cantareira, São Paulo -SP. Foram obtidas medidas de altura, diâmetro do coleto, número de folhas e volume do torrão das mudas. O transplante foi realizado em três condições de luminosidade depois de separadas em três classes de volume de torrão e três classes de diâmetro do coleto. Foram avaliadas a porcentagem de sobrevivência, incremento em altura, diâmetro do coleto, número de folhas e pigmentos fotossintéticos após 4, 8 e 12 meses. O delineamento experimental foi inteiramente casualizado em esquema fatorial 3 x 3 x 3 (luminosidade x diâmetros do coleto x volumes do torrão) com três repetições de cinco plantas cada. Os dados obtidos foram submetidos à análise de variância e as médias comparadas entre si através do teste de Tukey (5%). A sobrevivência foi superior a 80% em todos os ambientes. Houve maior crescimento, principalmente quanto ao diâmetro do coleto, na clareira pequena. A quantificação de clorofila a, b e carotenoides mostrou maior teor para as plantas mantidas no sombreamento. Quanto à razão clorofila a/b, os resultados evidenciaram maiores valores nas plantas mantidas no sombreamento, com valores crescentes até os 12 meses. Pode-se concluir que S. romanzoffiana apresenta pouca restrição quanto ao ambiente de realocação, porém, com preferência às clareiras pequenas, sendo dispensável que sejam realocadas com torrão de porte grande.
This study examined the effects of light intensity on the plasticity of the leaves of Juglans regia f. luodianense seedlings in karst habitat and how they respond to changes in light intensity. The light intensity of 1-year-old seedlings of J. regia f. luodianense in different niches in a karst area was set as 100% (bare land), 75% (forest margin), 50% (forest gap), and 25% (under forest) of natural light. The material harvested after four months was compared to analyze the differences in various morphological characteristics, biomass allocation, and physiological characteristics of the leaves of seedlings of J. regia f. luodianense, and a comprehensive evaluation of the plasticity indexes was conducted. The results showed that under moderate (50%) full light intensity, the leaf area, specific leaf area, leaf biomass, and chlorophyll content increased, and improved photosynthesis and promoted the accumulation of free proline content and peroxidase (POD) activity. The accumulation of malondialdehyde was also the lowest in this treatment, indicating that the plants had the strongest adaptability under this light intensity. Moreover, under high (75%) full light intensity, the above functional characteristics of plants showed good performance. Under low (25%) full light intensity, plants also had higher specific leaf area, leaf biomass, and photosynthetic parameters. However, under full light, the cell membrane permeability decreased, the chlorophyll accumulation was the lowest, and the photosynthetic index was seriously inhibited. Our results showed that the plasticity of morphological characters was greater than that of biomass allocation and physiological characters; POD activity and stomatal conductance were the highest, followed by leaf area and chlorophyll b, whereas the plasticity of palisade tissue/sponge tissue thickness and lower-epidermis thickness were the lowest. In summary, there are evident differences in the sensitivity and regulation mechanisms of morphological characteristics, biomass allocation, and physiological indices of the seedling leaves of J. regia f. luodianense in response to light intensity. During the stage of seedling establishment, only the plants in the bare ground under full light can be induced to show obvious inhibition of phenotypic traits. In contrast, the plants in the forest margins and gaps and under the forest habitats under light intensity can regulate their own characteristics to maintain their growth and development. The wide light range and strong plasticity of the species might be two of the important reasons for its existence in a highly heterogeneous karst habitat.
ABSTRACT Intercropping is a method of growing plants that assists in rational use of natural resources. Based on this concept, the aim of this study was to evaluate the response of collard green and radish ‘Cometo’ crops in monoculture and in intercropping under different spatial arrangements through physical production indicators (technical coefficients). The study was conducted in plant beds in a randomized block design (RBD) with 5 treatments and 4 replications. The treatments involved growing the two crops separately and intercropped under different spatial arrangements: (1:2) one row of radish ‘Cometo’ between two rows of collard green; (2:2) two rows of radish ‘Cometo’ between two rows of collard green; and (3:2) three rows of radish ‘Cometo’ between two rows of collard green. The spatial arrangements adopted did not affect the growth and development of radish ‘Cometo’ and of collard green, and all the arrangements used exhibited high land use efficiency, especially the 3:2 arrangement, which provided the greatest land use efficiency, at 1.69.
O presente estudo teve como objetivos determinar a melhor condição de sombreamento e o tipo de substrato para a produção de mudas e estabelecimento da simbiose espontânea por rizóbios em taxi-branco (Tachigali vulgaris). O experimento foi instalado no delineamento de blocos casualizados, com quatro repetições e os tratamentos arranjados em esquema de parcela subdividida, no qual a parcela consistiu de dois níveis de sombreamento (50% e 75%) e a subparcela de quatro tipos de substrato: solo; solo + areia (1:1); solo + areia + serragem (2:1:1); e solo + vermiculita (1:1). Cada parcela experimental foi constituída por cinco mudas. As mudas foram avaliadas quanto a um conjunto de variáveis morfológicas e fisiológicas, da parte aérea e da raiz. No final do experimento foi também realizado o isolamento e a caracterização fenotípica de bactérias oriundas de nódulos coletados nas mudas. A caracterização foi realizada pela avaliação morfológica das colônias. O sombreamento de 50% é o indicado na produção de mudas de taxi-branco, enquanto que, em relação ao substrato, aquele composto por solo + areia é o que proporciona mudas de melhor qualidade. A espécie apresentou simbiose com grande diversidade de rizóbios, apesar de o número de isolados não ter sido influenciado pelo tipo de substrato e nível de sombreamento. A maioria dos isolados obtidos apresentam tempo de crescimento muito rápido e pH ácido do meio de cultura.
RESUMO: Cada espécie tem exigências próprias para o seu desenvolvimento. Luz, água, temperatura são alguns dos elementos abióticos que influenciam no desenvolvimento das plantas. A luz é importante no desenvolvimento vegetativo por influir, entre outros processos, na taxa de fotossíntese; a intensidade, qualidade, duração e periodicidade da luz agem tanto quantitativa como qualitativamente no incremento da planta. Objetivou-se testar diferentes níveis de sombreamento no desenvolvimento de mudas de jatobá (Hymenaea courbaril var. Stilbocarpa). O experimento foi realizado em área aberta sendo as mudas produzidas em casa de vegetação do tipo Pad & Fan e transplantadas para sacos pretos de 5 litros aos 20 dias após a semeadura usando-se mistura de solo e composto orgânico (1:1) como substrato. O delineamento experimental foi inteiramente casualizado com quatro tratamentos e 13 repetições cada, uma planta por parcela. Os tratamentos foram: T1 = Pleno sol; T2 = Tela de sombreamento 30%; T3 = Tela de sombreamento 50%; T4 = Tela de manipulação de espectro de luz ChromatiNet ® vermelho 30%. As telas foram fixadas em telados de madeira de dimensões 1x1x1 m (altura x largura x comprimento). As características analisadas foram: altura das plantas, diâmetro médio do caule das plantas, teor de clorofila das folhas, relação altura de planta e diâmetro de caule, área foliar e massa fresca e seca de raiz e parte aérea. As melhores mudas de jatobá (Hymenaea courbaril var. Stilbocarpa) foram produzidas em sombreamento de 30 e 50% em 84 dias após o transplante. Palavras-chave: Telas de sombreamento. Espectro de luz. ChromatiNet ® vermelho. SHADING LEVELS IN Hymenaea courbaril var. Stilbocarpa SEEDLINGS DEVELOPMENT
A canafístula tem grande potencial econômico, contudo, as sementes apresentam dormência causada pela impermeabilidade do tegumento à água. Objetivou-se com este trabalho avaliar a eficácia de métodos para a superação
da dormência de sementes de canafístula. O delineamento experimental foi inteiramente casualizado com oito métodos de superação da dormência e quatro repetições. Cada unidade experimental foi constituída por 25 sementes, totalizando 100 sementes por tratamento. Foram avaliados seis métodos físicos (água quente a 95º C e, a permanência por 24 horas na mesma água, fora do aquecimento; fervura das sementes por 5 minutos; calor seco em estufa a 40 ºC por 24, 48, 72 e 96 horas), um mecânico (escarificação com lixa número 80) e o controle (sementes sem tratamento para superação da dormência). Avaliou-se a emergência, o tempo médio emergência e o índice de velocidade de emergência. Os tratamentos mais eficientes para superar a dormência de canafístula são a
imersão das sementes em água quente a 95º C e, a permanência por 24 horas na mesma água, fora do aquecimento e a escarificação com lixa no lado oposto ao hilo.
O uso de bactérias promotoras de crescimento de plantas pode melhorar o crescimento e o desenvolvimento das mudas de cana-de-açúcar devido a produção de sideróforos e hormônios vegetais e a capacidade de fixar nitrogênio. Este estudo foi realizado para investigar a eficiência da aplicação de doses de Azospirillum brasilense na produção de mudas pre‑brotadas (MPB) de ariedades de cana‑de‑acucar (Saccharum spp.). A pesquisa foi desenvolvida em casa-de-vegetação na Universidade Estadual de Mato Grosso do Sul – UEMS, em Cassilândia, MS. Foram utilizadas plantas de 12 dias, oriundas de minirrebolos de 3 cm de comprimento de quatro variedades de cana-de-açúcar, produzidas em bandejas plásticas contendo substrato comercial. As plantas foram transplantadas em tubetes plásticos de 290 cm3. O delineamento experimental utilizado foi o de blocos casualizados, disposto em esquema fatorial 4 × 5 com três repetições. Os tratamentos foram constituídos por quatro variedades de cana-de-açúcar (IAC-SP 95-5000, RB 86-7515, RB 85-5035 e RB 85-5536) e por cinco doses de aplicação do inoculante contendo A. brasilense [0 (controle); 0,5; 1,0; 2,0 e 4,0 mL por tubete]. Aos 65 dias após o transplante das plantas, foram mensurados o crescimento e o acúmulo de matéria seca. Os resultados reportaram que a aplicação de inoculante contendo A. brasilense durante a fase de formação de mudas melhorou o crescimento e o desenvolvimento das plantas das variedades de cana‑de‑acucar IAC-SP 95- 5000, RB 86-7515 e RB 85-5035. A dose ideal de aplicação de inoculante contendo A. brasilense para as variedades IAC-SP 95-5000, RB 86-7515 e RB 85-5035 pode variar entre 2 e 3 mL/tubete. A variedade de cana‑de‑acucar RB 85-5536 tem baixa resposta à inoculação com A. brasilense por ser uma variedade rústica com pouco resposta a ambientes de média-alta fertilidade.
RESUMO: Este trabalho teve como objetivo avaliar
a produção de massa verde e seca de diferentes
combinações de adubos verdes e sua influência
sobre as características agronômicas do feijão, cv.
Carioca, em sucessão. O trabalho foi realizado na
Fazenda Experimental “Professor Antônio Carlos
dos Santos Pessoa”, pertencente à Universidade
Estadual do Oeste do Paraná (Unioeste). O
delineamento experimental empregado foi o de
bloco ao acaso, com oito tratamentos e quatro
repetições, totalizando 32 parcelas, sendo os
tratamentos constituídos de diferentes adubos
verdes. Foram determinadas a massa verde e seca
dos adubos verdes e as características do feijoeiro,
como: estande final, altura da planta, altura de
inserção da primeira vargem, número de vagens
por plantas, comprimento longitudinal médio
das vagens, número de grãos por vagens, peso
de 1000 grãos, produtividade. Os dados obtidos
foram submetidos à análise de variância (ANOVA)
e as médias comparadas pelo teste de Tukey (P ≤
0,05). Em relação aos resultados de massa verde,
massa seca e características agronômicas foram
encontradas diferenças significativas entres
os tratamentos avaliados. Sendo que para a
produtividade de massa verde e seca dos adubos
verdes o consorcio entre as espécies de ervilhaca
peluda + nabo forrageiro foi o que apresentou
os maiores valores e para as características
agronômicas do feijoeiro os melhores resultados
foram obtidos após a sucessão do consorcio entre
as espécies Triticale tpolo + nabo forrageiro.
PALAVRAS CHAVES: Biomassa, Phaseolus vulgaris
L., Plantas de inverno.
Tamarind presents great economic importance in Brazil, and care at the time of fertilization in the initial growth of the seedlings should be taken, thus, slow release fertilizers, may be an option for the development of the crop by providing a continuous availability of nutrients to the long of the time, but the amount works of literature in this area is scarce, and research is needed to alleviate this situation. Thus, the objective of this work was to evaluate the initial growth of tamarind seedlings in doses of slow release fertilizer. The experiment was carried out in a greenhouse where the seedlings after germinated were transplanted into black polyethylene bags (2 liters), filled with substrate [soil + sand + organic compound (1:1:1)], added the higher and lower dose of the slow release fertilizer: Slow Release® (manufacturer's recommendation). The experimental design was completely randomized with 3 Treatments [T1-Control (No fertilization), T2-Slow Release® (1 g L-1), T3-Slow Release® (2 g L-1), with 5 repetitions. They were analyzed at 0 and 35 after transplantation: shoot height, shoot diameter and photosynthetic pigments (chlorophyll a, b and carotenoids). The results were submitted to analysis of variance and tukey test (5% probability). It was concluded that the slow-release fertilizers did not increase the height and stem diameter in the plants, being necessary evaluations with more than 35 days to possibly present difference between the Treatments, however, there was a great increase in the concentrations of pigments analyzed, especially T2.
The high luminosity rates and high annual average temperatures of the Brazilian semiarid region, combined with the use of irrigation and adaptability of the sunflower crop to local climate, favor increased achene yield due to acceleration of morphophysiological processes. The objective of this work was to evaluate the morphophysiological and productive characteristics of sunflower varieties grown under drip irrigation in the Sub-Mid São Francisco River Valley. The experiment was conducted in the Experimental Field of the Brazilian Agricultural Research Corporation (Embrapa Semiarid), in Petrolina, State of Pernambuco, Brazil, in a randomized block design, with 21 sunflower varieties and four replications. The variables evaluated were flowering time, plant height, number of live leaves, stem and capitulum diameter, number of lodged and broken plants, stem curvature, relative chlorophyll index, photosynthesis, stomatal conductance, transpiration, average leaf temperature, 1000-achene weight and achene yield of the sunflower varieties. The treatments presented flowering time of 43 to 59 days after sowing, plant height of 1.0 to 1.4 m, capitulum diameter of 0.154 to 0.221 m, chlorophyll content of 30.8 to 33.98 Spad units and 1000-achene weight of 35.61 to 80.30 g. The sunflower varieties V7 and V8 stood out, with achene yields above 2,960 kg ha⁻¹ and low number of lodged and broken plants, indicating a greater adaptability irrigation crops in the Sub-Mid São Francisco River Valley.
Keywords:
Helianthus annuus L.; Physiology; Biometry; Agronomic performance.
The use of coloured shading nets to improve plant development is a technique, which has received considerable recent interest due to positive responses obtained. In this context, photosynthetic pigments content and chloroplast characteristics of tamarind (Tamarindus indica) plants grown under coloured shade nets were examined. Under greenhouse, tamarind seeds were sown in polypropylene trays containing Plantmax® substrate. When the seedlings reached 10 cm long (approximately 60 d old), they were placed inside of structures covered with blue, red, white and black shade nets, with 50% of shading. After 150 d, the leaves were collected and chlorophyll and carotenoids content as well as chloroplast features were assessed. Plants grown under black net showed higher values for chlorophyll a and chlorophyll b content as well as for total chlorophyll and a/b ratio. The black net was also responsible for providing the highest density of chloroplasts and area of starch grains, while the chloroplast area was greater under blue and black nets. These results make the use of black net, a cultivation practice suitable for commercial purposes.
A análise do teor de clorofila na planta é utilizada para avaliar o efeito das condições nutricionais do solo e como indicativo de estresse. O objetivo deste trabalho foi apresentar uma simplificação da etapa de extração de pigmentos foliares em plantas de canola. O experimento foi conduzido em ambiente protegido e avaliado no Laboratório Multiuso do Curso de Agronomia da Universidade do Oeste de Santa Catarina, no município de São José do Cedro. Após a coleta e tamisamento de um Nitossolo eutrófico de textura argilosa, acondicionou-se em vasos em que foi semeada a canola. Na floração, coletou-se a quarta ou quinta folha abaixo da inflorescência principal, para a análise de pigmentos foliares. Depois de transportadas até o laboratório e lavadas com água destilada, obtiveram-se discos foliares, sendo ou não macerados com pistilo em almofariz. Estes foram transferidos para tubos de ensaio contendo solução extratora, nos quais permaneceram por 24 horas em câmara fria, protegidos da luz. Filtraram-se os extratos, e com a solução resultante, determinou-se a absorbância das amostras. Com as leituras, foram calculados os teores de clorofila a, b, a + b, total e a relação clorofila total/carotenoides. Nas condições do presente experimento, o método de extração sem maceração do tecido vegetal demonstrou-se simples e rápido, requer pouca manipulação e apresenta boa eficácia.
Objetivou-se determinar o tipo de substrato e as melhores condições de luminosidade para o cultivo de mudas de Tocoyena formosa (Cham. & Schltdl.) K. Schum. A semeadura ocorreu em bandejas de isopor sob sombrite de 70% e três meses após a emergência, as plântulas foram selecionadas e em seguida transplantadas em vasos de 4L, em dois tipos de substratos: 50% de solo Latossolo Vermelho Distroférrico + 50% de areia (TA) e 50% de solo de Latossolo Vermelho Distroférrico + 25% de areia + 25% de cama de frango semidecomposta (TACF). Após o transplante, as mudas foram levadas para três condições de sombreamento (30%, 50% e 70% de sombra) e a pleno sol (0%). Após a aclimatação, a qualidade fisiológica das mudas foi determinada mensalmente, através da análise de crescimento e do índice de qualidade de Dickson, durante 270 dias. O experimento foi realizado em DIC em esquema fatorial 2 x 4 x 4 (substratos x sombreamento x idade da muda), com três repetições de três mudas. Foi observado maior crescimento e qualidade das mudas em substrato terra + areia + cama de frango e nas condições de 30% de sombra e pleno sol. Conclui-se que para produção de mudas de Tocoyena formosa a melhor condição de luminosidade é 30% de sombra e em pleno solem substrato TACF.
O sistema de multiplicação rápida de batata doce em recipientes, a partir de
miniestacas contendo duas gemas, é adotado para produção de maior número de
mudas. Dessa forma, o objetivo deste trabalho foi avaliar dois níveis de
luminosidade e diferentes substratos na produção de mudas de batata doce. O
delineamento experimental utilizado foi o inteiramente casualizado, em esquema de
parcelas subdivididas, com dois níveis de luminosidade e quatro substratos, com
quatro repetições de 24 mudas. A parcela foi representada por dois níveis de
luminosidade: a sol pleno e sob tela sombrite 50% de restrição de luz; e a
subparcela por quatro substratos: terra+areia+esterco (TAE - 1:1:1 v/v), vermiculita,
fibra de coco e substrato comercial Olambra®. Foram avaliados estande final,
número de raízes e folhas, comprimento da maior raiz e maior folha, massa seca de
raízes e parte aérea, e razão raiz/parte aérea das mudas. A produção de mudas de
batata-doce a pleno sol proporciona maior estande final, número de folhas e massa
seca da parte aérea e de raízes. A produção de mudas de batata-doce em substrato
comercial Olambra® proporciona maior número de folhas, comprimento da maior
raiz, massa seca da parte aérea e de raízes, e razão raiz/parte aérea.
Water stress reduced dry matter accumulation in Ficus benjamina plants, especially those grown in the sun. Accumulation of carbohydrates and reduction of chlorophyll was associated with water stress in sun plants, but there were no stress related changes of carbohydrate or chlorophyll levels in plants grown under 47% shade. Electron micrographs of chloroplasts showed starch deposits and disruption of thylakoid structures with water stress in sun plants, while disruption due to water stress was less severe in shade-grown plants. Net photosynthesis (Pn) was lower for unstressed shaded plants, but interposure of water stress resulted in similar Pn levels for both light regimes. Photosynthesis was restored to non-stressed levels after irrigation in both sun and shade light treatments. Lowest light compensation points (LCP) occurred in shade plants with no influence due to water stress, but water stress caused high LCP in sun plants.
The physiology, morphology and growth of first-year Betula papyrifera Marsh., Betula alleghaniensis Britton, Ostrya virginiana (Mill.) K. Koch, Acer saccharum Marsh., and Quercus rubra L. seedlings, which differ widely in reported successional affinity and shade tolerance, were compared in a controlled high-resource environment. Relative to late-successional, shade-tolerant Acer and Ostrya species, early-successional, shade-intolerant Betula species had high relative growth rates (RGR) and high rates of photosynthesis, nitrogen uptake and respiration when grown in high light. Fire-adapted Quercus rubra had intermediate photosynthetic rates, but had the lowest RGR and leaf area ratio and the highest root weight ratio of any species. Interspecific variation in RGR in high light was positively correlated with allocation to leaves and rates of photosynthesis and respiration, and negatively related to seed mass and leaf mass per unit area. Despite higher respiration rates, early-successional Betula papyrifera lost a lower percentage of daily photosynthetic CO2 gain to respiration than other species in high light. A subset comprised of the three Betulaceae family members was also grown in low light. As in high light, low-light grown Betula species had higher growth rates than tolerant Ostrya virainiana. The rapid growth habit of sarly-successional species in low light was associated with a higher proportion of biomass distributed to leaves, lower leaf mass per unit area, a lower proportion of biomass in roots, and a greater height per unit stem mass. Variation in these traits is discussed in terms of reported species ecologies in a resource availability context.
O plantio de essências nativas, seja com finalidade econômica ou conservacionista, requer uma série de cuidados que dependem do conhecimento prévio de suas características fisiológicas e exigências ecológicas nas diversas etapas de seu ciclo vital. O estudo do crescimento e desenvolvimento de uma planta, em diferentes condições ambientais, oferece ao pesquisador bom indício sobre quais as melhores condições para se cultivar determinada espécie. Objetivou-se avaliar o crescimento inicial e as concentrações de clorofilas em plantas jovens de Cryptocaria aschersoniana Mez. (Canela-Batalha), submetidas a níveis de redução da radiação solar: 0% (Pleno Sol), 30%, 50% e 70%. Os resultados demonstram que o teor de clorofila total foi maior nas plantas cultivadas em 70% de sombreamento, o mesmo ocorrendo com a razão clorofila a/b. A maior altura foi apresentada pelas plantas cultivadas em 50% de sombreamento. Do ponto de vista de acúmulo de matéria seca total e matéria seca de raízes, a melhor performance foi observada nas plantas em 30% de sombreamento e o maior acúmulo de matéria seca de folhas verificado nas plantas cultivadas em 30 e 50% de sombreamento. Conclui-se que as melhores condições de cultivo para mudas de Cryptocaria aschersoniana Mez. (Canela-Batalha) foram os níveis de 30 e 50% de redução da radiação solar incidente.
RESUMO: Com o objetivo de avaliar os efeitos de períodos de sombreamento de mudas de fedegoso (Senna macranthera) sobre parâmetros morfológicos e índices de qualidade, foi instalado um experimento no viveiro de pesquisa do Departamento de Engenharia Florestal da Universidade Federal de Viçosa. O experimento seguiu um delineamento estatístico in- teiramente casualizado, com três repetições e tratamentos que variaram desde a produção a pleno sol até o sombreamento das mudas por 150 dias após a semeadura. Os resultados mostraram que houve um aumento de diâmetro do coleto (D), altura da parte aérea (H), sobrevivência (Sob), relação altura da parte aérea/diâmetro do coleto (H/D), produção de matéria seca da parte aérea (PMSPA), produção de matéria seca de raiz (PMSR), produção de matéria seca total (PMST), índice de qualidade de Dickson (IQD) e redução da relação al- tura da parte aérea/produção de matéria seca da parte aérea (H/PMSPA) com o aumento do período de sombreamento. Conclui-se que as mudas de fedegoso apresentam vantagens quando sombreadas nos primeiros 60 dias após a semeadura. PALAVRAS-CHAVE: Espécies florestais nativas, Qualidade de mudas, Sombreamento, Fe- degoso ABSTRACT: With the objective to evaluate the effect of periods of shading in fedegoso (Sen- na macranthera) seedlings on morphological parameters and quality index, an experiment was installed in the research nursery of the Forest Engineering Department of the Federal University of Viçosa. The experiment followed a randomized design, with three repetitions and treatments that had varied since the production the full sun until the shading of the seed- lings per 150 days the sowing. The results had shown that it had an increase of D, H, Sob, H/D, PMSPA, PMSR, PMST, IQD and reduction of H/PMSPA with the increase of the period of shading. One concludes that the fedegoso seedlings need to be shaded in first the 60 days the sowing.
Potted seedlings of Chinese tallowtree (Sapium sebiferum [L.] Roxb.) and Carolina ash (Fraxinus caroliniana Mill.) were grown in 5%, 20%, 53%, and 100% of full sunlight. Growth and dry mass partitioning at all light levels, differences between leaf photosynthetic systems developed at 20% and 100% light, and crown profiles of net photosynthesis (PN) in 53% of full sunlight were measured. Tallowtree dry mass peaked at 100%, light while ash dry mass peaked at 53% light. Expressed as a proportion of peak dry mass within species, growth of tallowtree exceeded that of ash at all light levels except 53% of full sunlight. In all but 100% light, tallowtree partitioned more dry mass to leaves than did Carolina ash. For plants grown in 100% light, PN was highly variable with low values in some tallowtree and most ash leaves, although highest PN occurred in ash. For plants grown in 20% light, PN was closely related to photosynthetic photon flux density (PPFD), and both species had similar PN Values at any given PPFD. For plants in 53% light, maximum PN occurred at the top of the crown in tallowtree and in the middle of the crown in Carolina ash. Tallowtree seedlings are shade tolerant and yet grow rapidly in full sun. For. Sci. 36(4):851-862.
The influence of irradiance on photosynthesis under natural conditions was studied in aseasonal Singapore using three Heliconia taxa: H. rostrata, H. psittacorum × H. spathocircinata cv. Golden Torch and H. psittacorum cv. Tay. When grown under full sunlight, all three heliconias exhibited reduced phatosynthetic capacities and lowered chlorophyll content per leaf area as compared with those grown under intermediate and deep shade. A marked decrease in the chlorophyll fluorescence Fv/Fm ratio and an increase in photochemical quenching (1- qp) and non-photochemical quenching (qN) were observed in upper leaves of plants grown under full sunlight. Increases in qN suggest that ‘photoinhibition’ (decreases in Fv/Fm) in Heliconia grown under natural tropical conditions are probably due to photoprotective energy dissipation processes. The quantum yield, the maximum photosynthetic rate, Fv/Fm and the chlorophyll content of upper leaves were lower than those of lower leaves on the same plants grown under full sunlight. Similarly, lower values were obtained for the tip (sun) portion than for the base (shaded) portion of the leaves. The changes in Fv/Fm and in the levels of (1 –qp) in leaves grown under intermediate and deep shade were negligible in plants during the course of day. However, there was a steep decrease in Fv/Fm and an increase in the levels of (1 –qp), along with an increase in incident light in the sun leaves. The lowest Fv/Fm and the highest level of (1 –qp) indicated minimum PSII efficiency at midday in full sun. These results indicate that, in Heliconia, the top leaves (particularly leaf tips) experienced sustained decreases in PSII efficiency upon exposure to full sunlight. Although all three taxa exhibited sustained decreases in photosynthetic capacity in full sunlight, the sun leaves of ‘Tay’ showed higher photosynthetic capacity than those of the other two taxa. This could be due, at least in part, to the vertical leaf angle and smaller lamina area. When the upright leaves of ‘Tay’ were constrained to a horizontal angle, they exhibited lower PSII efficiency (FvIFm ratio), while horizontal leaves of ‘Rostrata’ and ‘Golden Torch’ inclined lo near-vertical angles showed increased efficiency. Thus, an increase in leaf angle helps to achieve a reduction in the sustained decrease in PSII efficiency by decreasing the levels of incident sunlight and subsequently the leaf temperature.
The use of DMSO for the extraction and determination of chlorophylls a and b in lichens and higher plants was reevaluated. Because of differences between the absorption spectra of pure chlorophylls a and b in DMSO and 80% acetone, formulae to calculate the individual concentrations of chlorophyll a, chlorophyll b and total (a + b) chlorophyll in pigment extracts were redetermined for specific use with DMSO. In lichens, the problem of chlorophyll degradation resulting from the presence of acidic lichen substances was specifically addressed. Repeated washing of thalli with carbonate-saturated 100% acetone followed by extraction in DMSO containing PVPi minimized the conversion of chlorophylls to phaeophytin during extraction of chlorophylls from lichens for which the content of lichen substances was characterized. In lichens containing significant quantities of acidic compounds, the modified DMSO assay proved superior to 80% acetone for the extraction and determination of chlorophyll a and b concentrations. In a range of higher plants, determinations of chlorophyll a and b concentrations were virtually identical when the modified DMSO assay was compared with the traditional method of chlorophyll extraction using 80% acetone. Moreover, DMSO extracts could be cold-stored for up to 7 days with no significant loss of chlorophylls a or b, or changes in the a/b ratio. Potential eco-physiological applications of the modified DMSO assay, which eliminates the necessity for grinding plant material and centrifuging plant extracts, are discussed.
The extinction coefficients for chlorophylls a and b in diethylether (Smith, J.H.C. and Benitez, A. (1955) in Modern Methods of Plant Analysis (Paech, K. and Tracey, M.V., eds.), Vol. 4, pp. 143–196, Springer-Verlag, Berlin), used in this paper as primary standards, were verified, to within an error of less than 1%, by magnesium determination using atomic absorbance spectrophotometry. We also report the determination of accurate extinction coefficients for chlorophylls a and b in N,N′-dimethylformamide, methanol or buffered 80% aqueous acetone. Highly purified chlorophylls were used and methods were employed which not only minimize errors due to evaporation of the volatile solvents employed in their estimation but also eliminate variable micro-contamination by chlorophyll degradation products, a potential source of inconsistency between the extinction coefficients obtained in each of these three solvents. Using these new coefficients, expressed as both millimolar and specific coefficients, we have derived new simultaneous equations to obtain chlorophyll concentrations as nmol/ml and μg/ml, respectively. These equations were applied to data obtained with leaf discs from spinach and Flindersia brayleyana extracted with the three specified solvents and to a concentrated solution (in N,N′ -dimethylformamide) of a chlorophyll a + b mixture added to the threesolvent systems. The validity of these equations is proven by the consistency of the chlorophyll determinations and of the chlorophyll a/b ratios. New simultaneous equations, compatible with the equations derived for the threesolvents, are presented for the assay of chlorophylls a and b converted to their cyclic hydroxylactone derivatives by extraction with alkaline pyridine reagent (2.1 M pyridine in 0.35 M NaOH). Most chlorophyll analyses in higher plants, including the chlorophyll content and chlorophyll a/b ratios of plant thylakoids and chlorophyll-protein complexes, have been obtained in 80% aqueous acetone with the much used simultaneous equations of Arnon (Arnon, D.I. (1949) Plant Physiol. 24, 1–15). For this reason we include conversion factors whichcorrect these earlier data and make it compatible with data calculated with the simultaneous equations presented in this paper. The importance of these corrections to the formulation of meaningful models of the photosynthetic apparatus is demonstrated. Our results also indicate that grinding leaf discs with N,N′-dimethylformamide is a more reliable method for extracting all chlorophylls than shaking with this solvent for 24 h.
Photosynthetic pigments from Romalina duriaei were extracted by immersion of the thalli in dimethyl sulfoxide (DMSO). Extraction was complete and the extract was found to be stable in the dark at 4°C for 10 days. The extract was measured spectrophotometrically at the blue and red region of the absorption spectrum and the ratio OD435/OD415 mm was found to be a preferable parameter for estimating chlorophyll degradation to phaeopigments. It is shown that Arnon's equation for quantification of total chlorophyll can be used with DMSO extracts too.
An algorithm utilizing reflectance spectra bands in the photosynthetically active radiation (PAR) region of the solar spectrum was developed for the remote estimation of the concentrations of chlorophyll a, chlorophyll b, and carotenoids in soybeans. The defining of specific bands in the reflectance spectrum that corresponded to absorption bands of the individual pigments was basic to the development of the algorithm. The detection of these bands was rendered difficult by the lack of detail in reflectance spectra. It was therefore necessary to manipulate the reflectance spectra so that absorption bands due to specific pigments could be detected and their spectral maxima defined. It was found that by dividing soybean reflectance spectra by an arbitrarily selected reference soybean reflectance spectrum, ratio spectra were obtained in which the absorption bands could be distinctly seen and their wavelength defined. These ratio spectra allowed the defining of those bands corresponding to the absorption bands of chlorophyll a chlorophyll b, and carotenoids. The strong linear relationships of certain combinations of the bands in the ratio spectra to the concentrations of the photosynthetic pigments made it possible to develop a ratio analysis of reflectance spectra algorithm (RARS) by which the concentrations of these pigments could be calculated from the reflectance spectra. The measurements necessary for the development of RARS were made using soybeans which were grown at different nitrogen levels in order to obtain a range of reflectance spectra. A test of the RARS algorithm using other soybean plants showed very good agreement between measured pigment values and those calculated using RARS.
The influence of shading intensity on growth, morphology and leaf gas exchange of mangosteen (Garcinia mangostana L.) seedlings was investigated over a 2-year period. Diurnal gas exchange studies revealed significantly higher carbon gain
for leaves grown in 20 or 50% shade compared to leaves grown in 80% shade. Seedlings grown in 20 or 50% shade accumulated
significantly more dry weight than seedlings grown in 80% shade during the 2-year study period.
Seedlings grown in decreased shade showed decreased leaf size, increased leaf thickness, lower specific leaf area (SLA) and
higher stomatal frequency. Less shaded seedlings also allocated relatively more dry matter to roots than shaded seedlings
and exhibited a significant reduction in leaf area relative to total plant dry weight (leaf area ratio). Increased leaf number,
enhanced branching and shorter internodes resulted in a more compact appearance of less shaded seedlings. Irrespective of
light conditions, mangosteen seedlings exhibited inherently slow growth because of low photosynthetic rates per unit leaf
area, low SLA, low leaf area ratios and inefficient root systems.
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