When one leaf of a tomato plant is electrically-stimulated or heat-wounded, proteinase inhibitor genes are rapidly up-regulated in distant leaves. The identity of the systemic wound signal(s) is not yet known, but major candidates include hormones transmitted via the phloem or the xylem, the electrically-stimulated self-propagating electrical signal in the phloem (the action potential, AP), or the heat-wound-induced surge in hydraulic pressure in the xylem evoking a local change in membrane potential in adjacent living cells (the variation potential, VP). In order to discriminate between these signals we have adopted two approaches. The first approach involves applying stimuli that evoke known signals and determining whether these signals have similar effects on the "model" transcripts for proteinase inhibitors (pin) and calmodulin (cal). Here we show that a heat wound almost invariably evokes a VP, while an electrical stimulation occasionally evokes an AP, and both of these signals induce accumulation of transcripts encoding proteinase inhibitors. The second approach involves identifying the array of genes turned on by heat-wounding. To this end, we have constructed a subtractive library for heat-wounded tissue, isolated over 800 putatively up-regulated clones, and shown that all but two of the fifty that we have analyzed by Northern hybridization are, indeed, up-regulated. Here we show the early kinetics of up-regulation of three of these transcripts in the terminal (4th) leaf in response to heat-wounding the 3rd leaf, about 5 cm away. Even though these transcripts show somewhat different time courses of induction, with one peaking at 30 min, another at 15 min, and another at 5 min after flaming of a distant leaf, they all exhibit a similar pattern, i.e., a transient period of transcript accumulation preceding a period of transcript decrease, followed by a second period of transcript accumulation.
The rice (Oryza sativa L.) elongated uppermost internode (eui) gene effectively results in a recessive tall plant type. In eui background, we found a mutant 02428ha that exhibited a semidwarf phenotype. Because semidwarf varieties possess high yield
potential, this mutant may be useful for hybrid rice breeding. The present study aimed to characterize the dwarfing mechanism
in the mutant. Microscopic observation revealed that the cell length in the uppermost internode was reduced compared to the
wild type. The mutant showed a decreased sensitivity to exogenous gibberellin A3 (GA3) and gibberellin (GA) biosynthesis inhibitor, uniconazole. Meanwhile, it contained a high level of endogenous gibberellin
A1 (GA1). These results indicated that the semidwarf phenotype of 02428ha was caused by impairment of GA signal transduction rather
than by block in GA biosynthesis. Furthermore, expression analysis of genes involved in the GA signaling pathway showed that
transcript of GIBBERELLIN INSENSITIVE DWARF2 (GID2) was down-regulated in the mutant. Sequence analysis also revealed a 15-base pair (bp) insertion between base 594 and 595
in the coding region of GID2. Consequently, the reason for down-regulation expression of GID2 or sequence variation of GID2 might play roles in the phenotype of 02428ha.
Gibberellin insensitive dwarf 2 gene–Rice (Oryza sativa L.)–Semidwarf–Uppermost internode
Grape berries are considered recalcitrant materials in proteomic analysis, because berry tissues contain large amounts of
secondary metabolites, especially phenolic compounds, which severely interfere with protein extraction and electrophoresis
separation. We report hereby a PVPP/TCA-based protein extraction protocol for grape berries. Phenolic compounds in berry extracts
were removed with repeated PVPP cleanups, and proteins were recovered with TCA precipitation. Protein resolution in 2-D gels
was gradually improved with the increase of PVPP cleanup steps. By the protocol, about 760 protein spots of berry tissues
were clearly resolved in 2-D gels with CBB staining. This protocol was also used to analyze β-1,3-glucanase (EC 188.8.131.52)
in berry tissues. An anti-synthetic peptide antibody was prepared against 15 amino acid sequence residing on the surface of
β-1,3-glucanase molecule. It detected two major spots in 2-D blots of berry extracts. The spots were identified by MALDI-TOF
analysis as β-1,3-glucanase. The present study validates that β-1,3-glucanase is present in higher abundance in berry skins
than in pulps, and in red berries than in white berries. Therefore, β-1,3-glucanase displays a tissue-specific expression.
The preferential accumulation of β-1,3-glucanase in skins may be relevant to berry ripening.
The activities of chitinase, β-1,3-glucanase, peroxidase and phenylalanine ammonia lyase, constitutive and induced by Stagonospora nodorum were examined in the 10 – 14 day old seedlings of three triticale and two wheat cultivars under controlled environmental conditions and in flag leaves of two triticale cultivars in the field. Two S. nodorum isolates of different virulence were used. Both the constitutive and induced activities in triticale and wheat depended on genotype and in triticale the effect of growth conditions was also evidenced. The constitutive activities of chitinase, β-1,3-glucanase and peroxidase were several fold lower in flag triticale leaves in plants from the field than in the seedlings, growing under controlled conditions, but induction in the infected flag leaves was significantly more pronounced. In triticale genotypic differences in the response to infection were revealed only upon inoculation by S. nodorum isolate of higher virulence. The enzymatic activities increased several fold during successive days after the infection except for phenylalanine ammonia lyase. Induction of this enzyme was only transient and the activity decreased 48 or 96 h after infection when the activities of other enzymes were rising. In flag leaves in the field this activity was differentiated only after infection with more a virulent strain.
A tendency appeared in triticale seedlings for association of the resistance to the pathogen with lower enzymatic constitutive activities. This relationship became more evident in triticale infected by S. nodorum and may imply that although the investigated enzymes are certainly involved in general, non-specific defense mechanism, they do not decide on the resistance to pathogen at least in the early stages of infection and cooperate with other factors in the complex pathogen-plant interaction. One can also assume that the enzymatic activities are associated with severity of infection rather than resistance to pathogen.
Ascorbic acid (Asc) plays a multifunctional role in plants. l-galactono-1,4-lactone dehydrogenase (GLDH, EC 184.108.40.206) catalyzes the last step in the main pathway of Asc biosynthesis in
higher plants. In this paper, we first examined how a change in Asc content leads to a changed plant growth and seed set using
GLDH transgenic rice (Oryza sativa L.) which has different expression level of GLDH. The results showed that suppression of GLDH expression resulted in a loss
of chlorophyll, a lower Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 220.127.116.11) protein content, and a lower
rate of CO2 assimilation. As a consequence, a slower rate of plant growth and lower seed set were observed. Reduced seed set and growth
rate as measured by plant height, root length, leaf weight, and root weight were consistent with the GLDH-mediated reduction
of photosynthetic function. Increasing GLDH expression maintained high levels of chlorophyll, Rubisco protein, and a higher
rate of net photosynthesis, resulting in higher seed set. The observation that increasing the level of GLDH expression correlated
with reduced lipid peroxidation whereas reducing GLDH expression correlated with increased lipid peroxidation was consistent
with the foliar level of Asc, indicating that GLDH functions to protect against ROS-mediated damage. When taken together,
this work suggests that level of Asc in transgenic rice for GLDH is associated with plant growth and seed set.
l-galactono-1,4-lactone dehydrogenase–Plant growth–Seed set
The goal of this study was to investigate the contribution of increased activity of individual non-regulated enzymes in the
Calvin cycle to improve photosynthetic yield. Two non-regulated enzymes, rice fructose-1,6-bisphosphate aldolase (FBA) and
spinach triosephosphate isomerase (TPI), were individually cloned and overexpressed in the cyanobacterium Anabaena sp. strain PCC 7120 cells. The enzyme activity and the photosynthetic yield, as reflected by the cell growth rate, photosynthetic
oxygen evolution and dry cellular weight, were measured and compared between the wild-type and transgenic cells harboring
either FBA or TPI. Though the activity of these two individual non-regulated enzymes was similarly increased in the corresponding
transgenic cells, the contributions of each enzyme on the amount of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco),
reflected by the levels of Rubisco large subunit, and the photosynthetic yield were different. Transgenic cells, carrying
FBA, showed an evident increase in Rubisco amount and photosynthetic yield, while there was no increase in cells harboring
TPI. This indicates that the contributions of non-regulated enzymes in the Calvin cycle on photosynthetic yield differed and
firstly reveals that increased activity of only a single non-regulated enzyme in transgenic cells markedly improves the photosynthetic
yield via stimulating the amount of Rubisco and consequently accelerating the ribulose-1,5-bisphosphate (RuBP) regeneration
Effect of low (5 mmol·dm−3) and high (10 or 20 mmol·dm−3) doses of 1.10-phenanthroline (Phe), a photodynamic herbicide, on the development of chloroplasts in etiolated and subsequently
illuminated maize seedlings and on the structure of already developed chloroplasts of green maize seedlings was examined.
Etiolated and then irradiated plants were resistant to 5 mmol·dm−3 of Phe with respect to morphology, however Phe caused inhibition of greening and of grana formation. Higher Phe concentrations
followed by exposure to light caused not only total inhibition of greening but also dilation of thylakoids, swelling of chloroplasts,
and finally total destruction of chloroplast structure. Application of Phe in the same concentrations to green plants revealed
that they were resistant to low dose of Phe with respect to morphology and structure of chloroplasts, however 10 and 20 mmol·dm−3 Phe and illumination caused the loss of turgor of treated plants and other photooxidative damages seen at the ultrastructural
level. We concluded that maize, as representant of monocotyledonous plants, is resistant to low (5 mmol·dm−3) Phe concentration. Higher (10 or 20 mmol·dm−3) concentrations, used to determine the site of damage and mode of action of Phe on the level of cell revealed that action
of photodynamic herbicides is based on standard photoinhibition mechanism and also probably on their chelating properties.
Recently important epidemics caused by Alfalfa Mosaic Virus (AMV) have been reported in field grown canning tomatoes in southern
Italy. The Am resistance gene identified in Lycopersicon hirsutum PI 134417 confers a complete resistance to several isolates of AMV with different geographical and botanical origins. In
order to identify linked molecular markers, a segregant back-cross population of 120 individuals was obtained from the intraspecific
cross between the resistant L. hirsutum accession PI 134417 and the susceptible accession L. hirsutum PI 247087. Using bulked segregant analysis combined with AFLP technology, four AFLP markers were found to be linked to the
Am resistance gene. This gene will be assigned to a tomato chromosome using L. pennellii introgression lines.
The uptake rate of 14C-labelled sucrose, myo-inositol and PC was studied in callus cultures of two oilseed rape cultivars, characterized by different in vitro regeneration ability. Transfer of calli onto regeneration stimulating medium resulted in changes of examined substances uptake
rate, which were depended on tissue morphogenic potential. Non-regenerating calli of both cultivars increased uptake rate
of sucrose whereas changes in incorporation of other compounds were under genome control. Significant increase of uptake rate
of all tested compounds was observed as result of organogenesis initiation. Such differences, in the responses of organogenic
and non-organogenic tissue indicate that this parameter could be useful as marker of organogenesis
A correlation was observed between the rate of sucrose uptake and its concentration in the medium, which suggests an advantage
to passive transport through the callus cell membrane. Lack of such correlation in the case of other labels indicates that
this processes are selective and under cell control.
Wheat transformation technology has progressed rapidly during the past decade. Initially, procedures developed for protoplast isolation and culture, electroporation- and polyethylene glycol (PEG)-induced DNA transfer enabled foreign genes to be introduced into wheat cells. The development of biolistic (microprojectile) bombardment procedures led to a more efficient approach for direct gene transfer. More recently, Agrobacterium-mediated gene delivery procedures, initially developed for the transformation of rice, have also been used to generate transgenic wheat plants. This review summarises the considerable progress in wheat transformation achieved during the last decade.
An increase in food production is essential in order to sustain the increasing world population. This could be achieved by the development of higher yielding varieties with improved nutritional quality and tolerance to biotic and abiotic stresses. Although conventional breeding will continue to play a major role in increasing crop yield, laboratory-based techniques, such as genetic transformation to introduce novel genes into crop plants, will be essential in complementing existing breeding technologies.
A decade ago, cereals were considered recalcitrant to transformation. Since then, a significant research effort has been focused on cereals because of their agronomic status, leading to improved genetic transformation procedures (Bommineni and Jauhar 1997). Initially, the genetic transformation of cereals relied on the introduction of DNA into protoplasts and the subsequent production of callus from which fertile plants were regenerated. More recently, major advances have been accomplished in the regeneration of fertile plants from a range of source tissues, providing an essential foundation for the generation of transgenic plants. This review summarises procedures, vectors and target tissues used for transformation, high-lights the limitations of current approaches and discusses future trends. The citation of references is limited, where possible, to the most relevant or recent reports.
Two new T1BL.1RS translocation lines, 48112 and 89121, derived from cross between common wheat (Triticum aestivum L.) cultivar “Xiaoyan No. 6” and rye (Secale cereale L.) cultivar “German White”, were developed and identified by using of molecular markers and cytogenetical methods, GISH
and FISH. PCR results of primers NOR-R1 specific for rye and Glu-B3 for 1BS detected the presence of 1RS chromatin and absence of 1BS, and primer for gene 1Bx14 in 1BL indicated the existence of chromosome arm 1BL in the two lines. GISH and FISH methods confirmed the replacement of
chromosome arm 1BS with 1RS. Further stripe rust resistant test and quality analysis demonstrated that the new 1BL.1RS translocation
lines were higher resistant to mixed races of P. striiformis Westend and observed considerable better quality than other popularized T1BL.1RS cultivars in China. The two lines have been
used in wheat breeding for high-yield potential and rust resistance.
Callus cultures of Tabernaemontana persicariaefolia, (Apocynaceae), an endangered species endemic to the Mascarene Islands, were established from leaf explants on MS medium containing either
5 mg·l−1 2,4-D and 0.5 mg·l−1 BA or 5 mg·l−1 2,4-D, 0.5 mg·l−1 BA and 200 mg·l−1 DFMO. Histological studies showed regenerating nodules resembling globular embryos in calli after 4 weeks on the DFMO medium.
Green shoot formation was achieved by sequential subculture of the induced calli on media with gradually decreasing 2,4-D
concentrations (5→1→0 mg·l−1). Regeneration was greatly stimulated in the presence of DFMO. The first emergence of shoots occured 3 weeks earlier than
in untreated callus cultures.
To study the response of 20S proteasome in wheat (Triticum aestivum L.) roots to salt stress, the root tips from wheat seedlings treated with 200mM NaCl for different times were used for studying
its carbonyl level, caseinolytic activity, protein abundance and other biochemical characteristics. The contents of carbonylated
and ubiquitinated proteins (Ub-P) were also investigated. During this stressed process, both the productive rate of O2
− and the content of H2O2 gradually increased, with the concomitant increase in carbonyl level of total soluble proteins and 20S proteasome, together
with the gradual increase in the activities of the total and 20S proteasome in salt-treated root tips. However, the amounts
of 20S proteasome decreased particularly during this process. Moreover, metal-catalyzed oxidation of proteins from control
plants in vitro validated that the oxidative modification also could increase the activity of 20S proteasome, but decrease
its abundance. In addition, the amounts of Ub-P with molecular weights above 35kDa remained similar to the control plants,
but that below 35kDa decreased significantly in treated root tips. The changes in the proteasome activity and amount argue
in favor of the active involvement of this proteolytic system in salt-stressed plants.
Keywords20S proteasome–Caseinolytic activity–Reactive oxygen species–Salt stress–Ubiquitinated protein
Improvement on rice plant regeneration system from an embryogenic callus using two Malaysian indica rice MR 219 and MR 232
was developed in this study. Different stages of rice explants (zygotic embryos) were tested for callus induction and regeneration
using various carbon sources and amino acids. The present study shows that dough stage of zygotic embryos was the best stage
of explants for the embryogenic callus induction and regeneration of both rice cultivars. The embryogenic callus nature with
the compact structure was confirmed by scanning electron microscopy (SEM) analysis. Inclusion of maltose at the concentration
between 10 and 20mg/L shown higher responsive for the development of green somatic embryos and initiation of rice regeneration
with an average of 29–37 (87–91%) regenerated plantlets, respectively. All in vitro regenerated rice plantlets were green,
morphological and physiologically healthy condition. Rice plantlets were hardened in acclimatization room for 3weeks and
later transferred into soil with 95% survival in both varieties were recorded. Hence, regeneration system from zygotic rice
embryos via somatic embryogenesis system was carried out successfully by using 10g/L of maltose and combinations of glutamine,
asparagine and arginine amino acids.
KeywordsRice–Zygotic embryo–Somatic embryogenesis–Regeneration
The present study illustrates the effect of 24-epibrassinolide (24-EBL) on morphological and biochemical parameters in radish
(Raphanus sativus L.) seedlings grown under nickel (Ni) ion stress. The radish seeds pre-soaked in different concentrations of 24-EBL were
sown in petridishes containing various concentrations of heavy metal (Ni).Observations were made on root/shoot length, fresh
biomass, activities of antioxidant enzymes (ascorbate peroxidase, superoxide dismutase, catalase, monodehydroascorbate reductase,
dehydroascorbate reductase, guaiacol peroxidase and glutathione reductase), lipid peroxidation, proline and protein content
in 7-day-old Ni-stressed radish seedlings. Results indicate that seeds presoaked with 24-EBL reduced the impact of Ni-stress
which was evident by assessing the morphological parameters, protein content and antioxidant enzyme activities. It was also
observed that 24-EBL reduced the toxicity of heavy metal by influencing proline and malondialdehyde (MDA) content. The present
study lays a foundation for understanding the role of 24-EBL in heavy metal stress amelioration, particularly in food crop.
Analysis of behaviour of antioxidant enzymes will play a critical role in understanding the stress networking, further filling
the knowledge gap on the subject.
KeywordsAntioxidant enzymes–Radish–Nickel ion stress–24-epibrassinolide–Lipid peroxidation
The aim of this experiment was to study the effect of 24-epibrassinolide (BR27) on fatty acids composition and sugar content in winter oilseed rape callus cultured at 20 and 5°C. Studies have showed that
BR27 action is highly temperature-dependent. The increase in sugar content (sucrose, glucose and fructose) by BR27 in concentration 100nM was observed only in calli cultured at 20°C. At 5°C, quite the opposite effect of BR27 action was observed; where cold increased the sugar content, BR27 decreased it. BR27 at 20°C had a similar effect on the fatty acid composition of phospholipids (PL) as the cold in the process of frost hardening
of oilseed rape calli. BR27 decreased the 16:0, 18:1 and 18:2 and increased the 18:3 fatty acid content. At 5°C, BR27 (100nM) generally did not influence the fatty acid composition of PL. In case of digalactosyl diacylglycerols and monogalactosyl
diacylglycerols, the influence of BR27 on the fatty acid composition is ambiguous but still depends on temperature.
The present investigation recorded significant restoration of seedling growth (root length, shoot length and fresh weight)
upon application of 24-epibrassinolide (EBL) and putrescine (Put) to 7-day-old seedlings of Raphanus sativus L. cv. Pusa chetki grown under copper (Cu) ion stress. EBL and Put with/or without Cu ion treated seedlings showed increased
titers of ascorbic acid, total phenols and proline when compared with Cu-stressed seedlings. Differential responses in the
activities of guaiacol peroxidase (GPOX) and catalase (CAT) were noted for EBL and Put alone or with/or without Cu ion treatment.
Decreased activities of glutathione reductase (GR) and superoxide dismutase (SOD) noted for EBL and Put alone were observed
to enhance significantly when applied in combination with Cu ion solution. A remarkable decrease in malondialdehyde contents
was observed in seedlings treated with EBL and Put alone and with/or without Cu ion stress. Enhanced free radical scavenging
activities were also recorded for seedlings given EBL and Put alone or in combination over Cu ion stressed seedlings. Maximum
DPPH activity was observed in seedlings treated with Put and EBL 10−9M+Put. Significant enhancements in deoxyribose and reducing power activities were too recorded for Put, EBL and Put+10−9M EBL treatments. Improved seedling growth, antioxidant levels (ascorbic acid, total phenols and proline) and enzymic (GPOX,
CAT, SOD and GR) activities and free radical scavenging capacities along with reduced membrane damage in seedlings given EBL
and Put with/or without Cu stress suggests significant and positive interactions of EBL and Put in alleviating the Cu ion
induced oxidative damage in radish seedlings.
–24-Epibrassinolide–Polyamines–Antioxidative enzymes–Radical scavenging activity–Ascorbic acid–Lipid peroxidation
The objective of this study was to evaluate the effects of one of brassinosteroids (24-epibrassinolide) and clotrimazole,
(an inhibitor of brassinosteroid synthesis) on plant growth parameters, parameters related to leaf gas exchange (photosynthetic
and transpiration rates; stomatal conductance; water use efficiency), photosynthetic pigment content and osmolyte (sugars
and proline) content in Cajanus cajan exposed to salinity. Salt stress—caused by NaCl treatment—affected values of all parameters analyzed. The effects were ameliorated
by 24-epibrassinolide and intensified by clotrimazole. The hormone increased fresh mass of the plant, shoot dry mass, leaf
area, water content of leaves and roots, photosynthetic pigments, sugar concentration, photosynthetic rate, and water use
efficiency. The effects of hormone were less evident in the absence of salt. However, under this condition the application
of clotrimazole affected the values of parameters studied, indicating the importance of brassinosteroid synthesis for the
normal development of the plant.
KeywordsPigeon pea–Clotrimazole–24-epibrassinolide–Growth–Osmolytes–Photosynthesis–Salt stress
This paper presents a study of the metabolic response (dark respiration intensity, photosystem II efficiency, metabolic activity)
and the yield of barley treated with 24-epibrassinolide and subjected to high-temperature stress. Transport of exogenously
applied 24-epibrassinolide in barley and changes in the profile of brassinosteroids that may occur in tissues after 24-epibrassinolide
application were also studied. The water solution of 24-epibrassinolide (0.005 and 0.25mgdm−3) was applied via infiltration of the first and second leaves of 12-day-old seedlings. Control plants were treated with water
solution of hormone solvent (ethanol). Fifteen-day-old plants were subjected to high-temperature stress (42°C for 3h). The
influence of hormone treatment and stress conditions was investigated in the first and second leaves based on measurements
of PSII efficiency. The aftereffect of plant treatment was investigated in the seventh leaf (measurements of PS II efficiency,
dark respiration intensity, metabolic activity). The transport efficiency of 24-epibrassinolide exogenously applied to the
first and second leaves, as well as the profile of other brassinosteroids, was also measured on the seventh leaf. Finally,
yield formation was estimated. 24-epibrassinolide showed protective action, which manifested itself in the improved functioning
of PSII, but this was observed in case of higher hormone concentration and only for the first, older leaf. The PSII efficiency
of the seventh leaf was similar in plants treated with brassinosteroid and in the control plants, whereas the respiration
intensity and metabolic activity decreased in plants previously treated with higher concentration of 24-epibrassinolide. The
use of a higher hormone concentration at the seedling phase ultimately resulted also in lower crop yield. Brassinosteroids—brassinolide
and castasterone—were detected in barley leaves. 24-epibrassinolide was found only in trace amounts in control plants. Its
exogenous application directly to the apoplast of the first and second leaves resulted in an increase in the 24-epibrassinolide
content in the seventh leaf, but did not depend on whether a high or low concentration had been applied to the plants.
KeywordsBrassinosteroid transport–Dark respiration–
Hordeum vulgare L.–PSII efficiency–Metabolic activity–Yield
The effects of 28-homobrassinolide (28-homoBL) on seedling growth, lipid peroxidation and antioxidative enzyme activities
in the seedlings of Zea mays L. (var. Partap-1) under salt (NaCl) stress were studied. The surface-sterilized seeds were germinated in petriplates containing
different concentrations of NaCl (25, 50, 75 and 100mM) only, 28-homoBL (10−7, 10−9 and 10−11M) only and NaCl supplemented with 28-homoBL for 7days. The activities of superoxide dismutase (SOD, EC 18.104.22.168), guaiacol
peroxidase (POD, EC 22.214.171.124), catalase (CAT, EC 126.96.36.199), ascorbate peroxidase (APOX, EC 188.8.131.52) and glutathione reductase
(EC 184.108.40.206) were analysed in 7day-old seedlings. It was observed that 28-homoBL treatments reduced the toxicity of salt
on seedling growth considerably. Lipid peroxidation level was significantly increased under saline stress, but lowered with
28-homoBL applications revealing less oxidative damage. Further 28-homoBL treatments to the seedlings showed an enhancement
in activities of SOD, POD, CAT and APOX. The activities of all antioxidative enzymes were further increased in seedlings treated
with solution containing 28-homoBL and salt together as compared to seedlings treated with different concentration of salt
An experiment was conducted under controlled conditions, in which grains of wheat (Triticum aestivum L. cv. Raj-3077) were soaked in 0, 1, 3 and 5 µM aqueous solutions of 28-homobrassinolide (HBR) for 4, 8 and 12 hours. The
seedlings raised from the grains pre-treated with HBR possessed significantly higher leaf number, fresh and dry weight·plant−1, nitrate reductase (NR,E.C. 220.127.116.11) and carbonic anhydrase (CA, E.C. 18.104.22.168) activities on 25 and 35 days, after sowing.
The soaking of the grains in 3 µM concentration for 8 or 12 hours produced the most vigorous seedlings.
Recent biochemical and genetic studies on hydrogen cyanide (HCN) metabolism and function in plants were reviewed. The potential
sources of endogenous cyanide and the pathways of its detoxification are outlined and the possible signaling routes by which
cyanide exerts its physiological effects are discussed. Cyanide is produced in plant tissues as the result of hydrolysis of
cyanogenic compounds and is also released as a co-product of ethylene biosynthesis. Most cyanide produced in plants is detoxified
primarily by the key enzyme β-cyanoalanine synthase. The remaining HCN at non-toxic concentration may play a role of signaling
molecule involved in the control of some metabolic processes in plants. So, HCN may play a dual role in plants, depending
on its concentration. It may be used in defense against herbivores at high toxic concentration and may have a regulatory function
at lower concentration. Special attention is given to the action of HCN during biotic and abiotic stresses, nitrate assimilation
and seed germination. Intracellular signaling responses to HCN involve enhancement of reactive oxygen species (ROS) generation
and the expression of cyanide-insensitive alternative oxidase (AOX) and ACC synthase (ACS) genes. The biochemical and cellular mechanisms of these responses are, however, not completely understood.
To investigate the effect of exogenously applied 28-homobrassinolide (HBL) on drought-stressed plants, photosynthesis and
antioxidant systems were examined in Indian mustard (Brassica juncea L.). Seedlings of Indian mustard were subjected to drought stress for 7days at the 8–14 (DS1)/15–21 (DS2)days’ stage of
growth and then returned to normal conditions of growth. These seedlings were sprayed with HBL (0.01μM) at the 30-day stage
and were sampled at 60days to assess the changes in growth, photosynthesis and antioxidant enzymes. Plants exposed to stress
at either of the stages of growth exhibited a significant decrease in growth and photosynthesis. The exposure of plants to
stress at an earlier stage (DS1) was more inhibitory than that at a later stage (DS2). However, the follow-up treatment with
HBL significantly improved the values of these parameters and also overcame the inhibitory effect of water stress. The activity
of antioxidant enzymes [catalase (E.C. 22.214.171.124), peroxidase (E.C. 126.96.36.199) and superoxide dismutase (E.C. 188.8.131.52)] and
proline content in leaves exhibited an increase in response to both the treatment factors, where their interaction had an
additive effect. It was, therefore, concluded that the elevated antioxidant system, at least in part, was responsible for
amelioration of the drought stress.
The cell cultures of Cayratia trifolia (Vitaceae) a tropical lianas, were maintained in Murashige and Skoog’s medium containing 0.25mgl−1 naphthalene acetic acid, 0.2mgl−1 kinetin and 250mgl−1 casein hydrolysate. Cell suspension cultures of C. trifolia accumulate stilbenes (piceid, resveratrol, viniferin, ampelopsin) which on addition of 0.1–0.5mgl−1 morphactin in the medium containing naphthalene acetic acid and kinetin declined. Morphactin or 2 isopentenyl adenine alone
at 0.1mgl−1 concentration enhanced stilbenes which on combination markedly enhanced the yield to ~5mgl−1 at 15th day.
Basil (Ocimum basilicum L., cultivar Genovese) plants were grown in Hoagland solution with or without 50mM NaCl or 25mM Na2SO4. After 15days of treatment, Na2SO4 slowed growth of plants as indicated by root, stem and leaf dry weight, root length, shoot height and leaf area, and the
effects were major of those induced by NaCl. Photosynthetic response was decreased more by chloride salinity than by sulphate.
No effects in both treatments on leaf chlorophyll content, maximal efficiency of PSII photochemistry (F
m) and electron transport rate (ETR) were recorded. Therefore, an excess of energy following the limitation to CO2 photoassimilation and a down regulation of PSII photochemistry was monitored under NaCl, which displays mechanisms that play
a role in avoiding PSII photodamage able to dissipate this excess energy. Ionic composition (Na+, K+, Ca2+, and Mg2+) was affected to the same extent under both types of salinity, thus together with an increase in leaves Cl−, and roots SO4
2− in NaCl and Na2SO4-treated plants, respectively, may have resulted in the observed growth retardation (for Na2SO4 treatment) and photosynthesis activity inhibition (for NaCl treatment), suggesting that those effects seem to have been due
to the anionic component of the salts.
KeywordsBasil–Chlorophyll fluorescence–Gas exchange–Growth–Mineral composition–Salt stress
Common buckwheat (Fagopyrum esculentum Moench) is well known as a weed suppressing crop due to its strong competitive and allelopathic characteristics. The possible
allelopathic compounds in buckwheat include compounds from different groups, such as flavonoids, fatty acids, phenolic acids,
etc. Less attention has been paid to other phenolic compounds, specifically eugenol, o-eugenol, coniferyl alcohol and 3,4,5-trimethoxyphenol as possible allelochemicals. The effects of eugenol, o-eugenol, coniferyl alcohol, and 3,4,5-trimethoxyphenol on germination and plant growth were tested on seven plant species.
The results of our study showed that eugenols, coniferyl alcohol, or 3,4,5-trimethoxyphenol are minority components of the
buckwheat plant. Eugenol reached the highest concentration (1.16μg/g DW in buckwheat leaves) from these compounds and they
probably do not have a significant function in the allelopathy of common buckwheat. However, due to the inhibitory effects
on germination and plant growth, eugenol could be utilized in the plant protection of sustainable agriculture.
–Phenolic compound–Weed–GC–MS analysis
The radioactive precursor, [3-3H]oleanolic acid was administrated to excised roots from four weeks old Calendula officinalis L. plants. Transformations of this compound into two series of its glycosides, i.e. glucosides and glucuronides were investigated. For the first time it has been shown that both series of oleanolic acid glycosides
are synthesized in roots of young marigold plants. The pathway of their biosynthesis seems to be similar, although not identical,
to the pathway occurring in green organs of C. officinalis.
Sweet orange is an important group of citrus cultivars, which includes a number of bud sport cultivars. Little is known about
the CpG methylation status of the CCGG sequences in the orange genome. In this study, methylation-sensitive amplification
polymorphism (MSAP), based on the application of isoschizomers (Hpa II and Msp I), was first used to analyze cytosine methylation patterns in 57 orange cultivars that were not fully differentiated by
regular DNA molecular markers. Three types of bands were generated from ten primer pairs. Type I bands were present following
restriction with Eco RI+Hpa II and Eco RI+Msp I; type II or type III were present only following restriction with either Eco RI+Hpa II or with Eco RI+Msp I. The total number of these three types of bands was 802, 72, and 157, respectively. Among these, the number of polymorphic
bands were 244 (30.2%), 23 (31.9%), and 32 (20.4%), in type I, II and III, respectively. The methylation patterns of these
57 cultivars are discussed and assessed by dendrograms derived from the analysis of polymorphic MSAP bands. The distribution
of polymorphic bands of the above three types demonstrate the methylation patterns and frequency at the cytosine loci. We
suggest that methylation events could be more frequent than demethylation events, and that the methylation patterns maybe
associated with phenotypic traits.
The influence of boron starvation on the root exudates content in soybean seedlings (Glycine max. L. Merr.) and the effect of exudates pretreatment on the pre-infection processes in symbiotic system Br. japonicum strain 636 and soybean were investigated. Root cell membrane stability of boron starved soybean plants (-B) decreased compared
to the control. The concentrations of all analyzed metabolites (reducing sugars, free amino acids, organic acids, soluble
phenols and total flavonoids) from root exudates of -B plants were lower than the control concentrations. Analysis of polyphenols
after HPLC chromatography of root exudates showed significant difference of peak numbers between chromatograms of exudates
obtained from boron starved and from control plants.
Bacterial culture treatment with root exudates from -B plants showed decreased growth, chemotaxis and attachment ability toward
the host root compared to the control exudate treatments. These changes were accompanied by decreased nodulation and acetylene
reduction activity of boron starved soybean plants.
The objective of this research was to study the effect of the chelated form of the iron salt of ethylenediamine di-o-hydroxyphenylacetic acid (Fe-EDDHA) (6% Fe) on in vitro rooting of the rootstock GF-677. The iron salt of ethylenediamine
tetraacetic acid (Fe-EDTA) (12% Fe) of the MS basic medium was replaced by Fe-EDDHA, which was applied in three concentrations:
93.5, 187.0 and 280mgl−1 (5.6, 11.2 and 16.8mgl−1 Fe, respectively). For each treatment of Fe-EDDHA, the effect of ascorbic acid added in four concentrations (0, 0.1, 1.0
and 10mgl−1) was studied. After 4weeks of culture, the explants growing on the medium with 280mgl−1 Fe-EDDHA gave the best rooting results. Regarding ascorbic acid, no clear stimulating effect on rooting was found.
Completion of rice genome sequencing has necessitated identification of transcripts encoded by the genome and their corresponding
functions. In the present study we have catalogued cytoplasmic ribosomal protein complement of rice genome corresponding to
68 families. Mining TIGR (The Institute for Genomic Research) rice database and unigene sequences available from National
Centre for Biotechnology Information (NCBI) produced a non-redundant set of these sequences. This resulted in identification
of 209 candidate r-proteins of which 22 have not been reported previously. The number of genes per family ranges from 1 to
8 distributed throughout the genome with maximum occurrence at chromosome 7. Mapping of r-proteins on BAC clones revealed
several small clusters of genes. Unigene sequences corresponding to most of the reported r-proteins were identified indicating
these genes are being expressed.
Cyanobacteria have a tremendous activity to adapt to environmental changes of their growth conditions. In this study, Synechocystis sp. PCC 6803 was used as a model organism to focus on the alternatives of cyanobacterial energy metabolism. Glucose oxidation
in Synechocystis sp. PCC6803 was studied by inactivation of slr1843, encoding glucose-6-phosphate dehydrogenase (G6PDH), the first enzyme
of the oxidative pentose phosphate pathway (OPPP). The resulting zwf strain was not capable of glucose supported heterotrophic growth. Growth under autotrophy and under mixotrophy was similar
to that of the wild-type strain, even though oxygen evolution and uptake rates of the mutant were decreased in the presence
of glucose. The organic acids citrate and succinate supported photoheterotrophic growth of both WT and zwf. Proteome analysis of soluble and membrane fractions allowed identification of four growth condition-dependent proteins,
pentose-5-phosphate 3-epimerase (slr1622), inorganic pyrophosphatase (sll0807), hypothetical protein (slr2032) and ammonium/methylammonium
permease (sll0108) revealing details of maintenance of the cellular carbon/nitrogen/phosphate balance under different modes
KeywordsCitric acid-Glucose-G6PDH-OPPP-Succinic acid-
Interspecific somatic hybrids between a dihaploid potato clone H-8105 susceptible to Phytophthora infestans (Mont.) de Bary and a resistant diploid tuberizing species Solanum bulbocastanum were generated and analysed. Only ten regenerants displaying the intermediate morphology with dominating characteristics
of the wild parent (simple leaves, anthocyanin pigmentation) were produced in 15 weeks after a single PEG-mediated fusion
event. The RAPD patterns confirmed the hybridity of all of them. The hybrids rooted poorly and grew slowly in vitro. The cytological analysis revealed a high degree of aneuploidy in the hybrids with morphological and growth anomalies in vitro, while the morphologically normal hybrids were tetraploids. All the S. bulbocastanum (+) H-8105 hybrids were unstable in culture and three of them were consequently lost during three years of propagation in vitro. The possible reasons for instability of somatic hybrids between the distantly related species are discussed.
The morphological, cytological and molecular analyses of the plants regenerated after PEG-induced fusion between mesophyll
protoplasts from the dihaploid potato clone H-8105 and the wild tuberous disease-resistant species S. pinnatisectum, were performed. A single fusion experiment yielded 313 calli, although only two calli produced shoots. From the rooted shoots,
two stable clones (PT-01-1 and PT-01-2) exhibiting different vigor and habitat, were developed. The plants of PT-01-1 clone
grew slowly in vitro, produced tubers after transfer to soil but did not set flowers. In contrast, the plants of the vigorous clone PT-01-2 produced
both tubers and flowers after transfer to soil. The flower and tuber morphology of PT-01-1 and PT-01-2 regenerants was intermediate
in comparison to the parental species. Cytological analysis revealed that the PT-01-1 clone was pentaploid and the PT-01-2
clone was tetraploid. The molecular (RAPD) analysis confirmed hybridity of both clones. The preliminary tests on late blight
resistance of the hybrids showed no differences with a potato parent.
In response to Clostera anachoreta larvae attack, poplar (Populus simonii×P.pyramidalis ‘Opera 8277’) leaves produced a high level of hydrogen peroxide (H2O2). Histochemical localization revealed that H2O2 was mainly localized in herbivore-wounded zones and might spread through the veins. The activities of three H2O2-scavenging enzymes, i.e., peroxidase (POD), ascorbate peroxidase (APX), and catalase (CAT), were also enhanced in herbivore-wounded
leaves, and exhibited an opposite pattern to the accumulation of H2O2. It was found that diphenylene iodonium chloride (DPI, a special inhibitor of NADPH oxidase) treatment significantly inhibited
the accumulation of H2O2 induced by herbivory damage. Moreover, DPI treatment led to an obvious decrease in the activities of POD, APX, and CAT. The
results indicated that NADPH oxidase contributed to the accumulation of H2O2 and the increase in activities of H2O2-scavenging enzymes in poplar leaves induced by herbivory damage. The balance between H2O2-production pathway and H2O2-scavenging enzymes led to the tolerable level of H2O2 acting in P.simonii×P.pyramidalis ‘Opera 8277’ cuttings in response to herbivory damage.
Changes in activity of phospholipase A2 (PLA2), a key enzyme in lipid metabolism and signal network in defence mechanisms, were investigated in Solanum species and Phytophthora infestans interaction. We have compared PLA2 activity in response to an elicitor, a culture filtrate (CF) derived from P. infestans, in non-host resistant Solanum
nigrum var. gigantea, field resistant S. tuberosum cv Bzura and susceptible S. tuberosum clone H-8105. To elucidate the contribution of specific forms of PLA2 to plant defence mechanism reasonably selective PLA2 inhibitors, haloenol lactone suicide substrate (HELSS) and p-bromophenacyl bromide (BPB), which discriminate between Ca+2-independent PLA2 (iPLA2) and Ca+2-dependent secretory PLA2 (sPLA2), were used. The in vivo and in vitro effects of the inhibitors on PLA2 activity and on generation of reactive oxygen species (ROS) induced by CF in the studied plants were assayed. We found that
PLA2 activity increased in response to CF treatment, displaying various kinetics and intensity depending on the resistance status
of a given genotype. Differences among the genotypes in the effects of each inhibitor on CF-induced PLA2 activity and on ROS production may reflect the diversity of PLA2 isoforms in plants. Contrary to BPB, the inhibitory effect of HELSS was observable mainly on CF-induced PLA2 activity, which suggests that iPLA2 participates in signal transduction in defence reactions. Various effects of the two inhibitors on PLA2 activity and ROS production suggest different contribution of sPLA2 and iPLA2 to modulation of defence reactions in the interaction between Solanum genotypes and P. infestans.
The aim of this work was to examine the ability of ABA and proline to counteract the deleterious effect of water deficit stress
on cell membrane injuries.
Six-day-old seedlings of two barley genotypes (cv. Aramir, line R567) were treated with ABA (2·10−4 M) or proline (0.1 M) for 24 h, and then subjected to osmotic stress for 24h, by immersing their roots in polyethylene glycol
(PEG 6000) solution of osmotic potential of −1.0 MPa and −1.5 MPa or by submerging the leaf pieces in PEG solution of osmotic
potential of −1.6 MPa.
Pretreatment of plants with ABA and proline caused an increase of free proline level in the leaves. Plants treated with ABA
exhibited a lower membrane injury index under water stress conditions than those untreated even when no effect of this hormone
on RWC in the leaves of stressed plants was observed. Pretreatment of plants with proline prevented to some extent membrane
damage in leaves of the stressed seedlings, but only in the case when stress was imposed to roots. Improvement in water status
of leaves was also observed in seedlings pretreatment with proline. The protective effect of both ABA and proline was more
pronounced in line R567 that exhibited higher membrane injury under water deficit stress conditions.
Exogenously applied ABA-β-d-glucopyranosyl ester (ABA-GE) inhibited shoot growth of alfalfa (Medicago sativa L.), cress (Lepidium sativum L.), lettuce (Lactuca sativa L.), Digitaria sanguinalis L., timothy (Pheleum pratense L.) and ryegrass (Lolium multiflorum Lam.) seedlings at concentrations greater than 0.1μM. The growth inhibitory activity of ABA-GE on these shoots was 26–40% of
that of (+)-ABA. ABA-β-d-glucosidase activities in these seedlings were 11–31nmolmg−1proteinmin−1. These results suggests that exogenously applied ABA-GE may be absorbed by plant roots and hydrolyzed by ABA-β-d-glucosidase, and liberated free ABA may induce the growth inhibition in these plants. Thus, although ABA-GE had been thought
to be physiologically inactive ABA conjugate, ABA-GE may have important physiological functions rather than an inactive conjugated
Soil salinity is one of the most significant abiotic stresses limiting plant growth. The ability of plant cells to adapt and
survive under salt stress conditions involves triggering a network of signaling events including hormones such as abscisic
acid (ABA) known to regulate many important aspects of growth and development. ABA is also known to play a critical role in
stress responses such as the regulation of seed germination under salt and osmotic stress. Components of the gibberellic acid
(GA) signaling pathway have also been shown to regulate germination; however, the involvement of GA signaling in salt and
osmotic stress is largely unexamined. Here, we examined the responses of mutants in the GA signaling pathway (rgl2 and spy) and in the ABA signaling pathway (abi3 and abi5) to salt (NaCl) and osmotic (mannitol) stress during seed germination and early seedling development. Several mutants show
resistance to increased levels of both salt and osmotic stress at germination and later stages of seedling development suggesting
a role for ABA and GA signaling in these processes. qRT-PCR was employed to determine the effect of salt stress on seed germination
via transcriptional control of the components in GA or ABA signaling pathways. We found that RGL2, ABI3, and ABI5 transcripts
are greatly induced by NaCl in wildtype plants, but show little if any induction by NaCl in mutant backgrounds suggesting
that this regulation of induction during salt stress may occur through ABA–GA crosstalk. Overall, our results indicate that
each of the ABA and GA signaling pathways is individually involved in regulation of various seedling developmental stages
under stress conditions. In addition, these two hormone pathways appear to be interacting in the regulation of germination
and early seedling growth under salt and osmotic stress conditions.
–Germination–Gibberellic acid–Salt signaling
This paper is a continuation of our studies related to the response of two tomato cultivars: Robin and New Yorker to chilling:
the later is more tolerant to chilling than the former one (Starck et al. 1994). The concentration of ABA in the xylem sap and ABA delivery rate (calculated as the amount of ABA exuded in 2h from
the cut stump, following shoot removal) were estimated by ELISA. The relative water content (RWC) of the leaf blades and stomatal
resistance (RS) were also measured. Tomato plants were grown in a greenhouse, under noncontrolled conditions. Before chilling
some of the plants were drought hardened for 10 days (H). As an consequence of water deficit only New Yorker growth slightly
decreased. Plants were chilled to 2–5 °C during three consecutive, 16-h nights, preceded by warm days, which caused a decrease
in the RWC of leaf blades. Chilling did not decreased leaf blade hydration significantly, but drastically increased the concentration
of ABA in the xylem sap in more chilling tolerant cv. New Yorker only. The delivery rate of ABA was markedly enhanced in both cultivars, but much more in New Yorker. Drought hardening
increased ABA delivery rate in cv. Robin only, especially after chilling. The lack of correlation between changes in the RWC of leaf blades after low temperature
treatment and the concentration of ABA in the xylem sap as well as its delivery rate suggest, that in both tomato cultivars
chilling increased ABA level directly, not as an secondery effect of temperature-induced water deficit.
The influence of exogenous abscisic acid (ABA) on the content of free polysomes (FP), membrane-bound polysomes (MBP), cytoskeleton-bound
polysomes (CBP) and cytomatrix-bound polysomes (CMBP) in triticale germs as well as in vitro protein synthesis by these four
polysomal fractions were studied. During translation, proteins were biotinylated for chemiluminescence detection. We have
found that ABA changed both the content of FP, MBP, CMP and CMBP in germ tissue, and their subsequent translation activity.
At 100μM ABA, the content of FP and MBP was over fourfold lower compared to the control, whereas the amounts of CBP and CMBP
were about two- and threefold higher, respectively. Moreover, the estimation of the share of polysomes in each ribosomal fraction
(sub-units, monosomes, polysomes) showed that, at 100μM ABA, cytomatrix-bound polysomes, which constituted 90% of polysomes,
were the predominant class in ABA-treated germs while membrane-bound polysomes, which made up 82% of polysomes, dominated
in the control. A high level of CMBP in ABA-treated tissues may indicate that this class of polysomes participates in ABA-induced
synthesis of proteins. In turn, the inhibition of MBP under ABA-treatment is probably due to the delayed protein synthesis
which takes place on these polysomes. We identified two lysine-containing proteins synthesized on both of the above classes
of polysomes, whose synthesis was altered due to ABA application. Synthesis of a 47kDa protein on MBP was inhibited, while
synthesis of a 79kDa protein on CMBP is strongly enhanced by ABA influence. The importance of these findings is discussed.
KeywordsAbscisic acid–Cytomatrix-bound polysomes–Germination–Lysine-containing proteins–Triticale caryopses
Molybdenum-containing aldehyde oxidase is a key enzyme for catalyzing the final step of abscisic acid (ABA) biosynthesis in
plants. Sulfuration of the molybdenum cofactor (MoCo) is an essential step for activating aldehyde oxidase. The molybdenum
cofactor sulfurase (MCSU) that transfers the sulfur ligand to aldehyde oxidase-bound MoCo is thus considered an important
factor in regulating the ABA levels in plant tissues. In this study, we identified the rice MCSU cDNA (OsMCSU), which is the first MCSU gene cloned in monocot species. According to the functional domain analysis of the predicted amino acid sequence, the OsMCSU
protein contains a Nifs domain at its N-terminus and a MOSC domain at the C-terminus. Expression of the OsMCSU gene was up-regulated by salt stress in root tissues of rice seedlings, but this effect was not observed in leaf tissues.
In roots, regulations of OsMCSU expressions could be mediated by both ABA-dependent and ABA-independent signaling pathways under salt stress condition.
In response to water deficit, endogenous abscisic acid (ABA) accumulates in plants. This ABA serves as a signal for a multitude
of processes, including regulation of gene expression. ABA accumulated in response to water deficit signals cellular as well
as whole plant responses playing a role in the pattern of gene expression throughout the plant. Although the function of genes
regulated by ABA during stress are currently poorly understood, a number of these genes may permit the plant to adapt to environmental
Drought stress causes yield loss in rice by inhibiting panicle exsertion which is driven by peduncle elongation near flowering.
To elucidate the mechanism of peduncle elongation, we examined the drought sensitivity of corresponding genes encoding xyloglucan
endotransglycosylase/hydrolase (XTH), a cell wall-loosening enzyme essential for cell elongation in the peduncle elongation
zone at heading stage. When drought was imposed 6days before heading, peduncle elongation rate (PER) was inhibited significantly
at heading and 1day after heading. Eleven OsXTH genes were isolated and their expression in rice peduncle determined. The expression of 11 OsXTH genes showed different patterns of response to drought stress. OsXTH3 was completely suppressed by drought. Transcript levels for OsXTH19, -20, -24, -27 and -28 genes were markedly down-regulated at a series of drought stresses. By contrast, OsXTH5 was up-regulated. Also, the behavior of leaf gas exchange and peduncle abscisic acid (ABA) level was determined under drought
conditions. The results indicated that stomatal conductance was 83% lower than that in control plants and peduncle ABA increased
ninefold with drought stress. Peduncle ABA content correlated highly with leaf stomatal conductance and PER (r=0.85** and 0.88**). The expression in OsXTH5, -19, -20, -24 and -28, corresponded to changes in PER and ABA. We conclude that ABA could be involved in inducing the retardation of PER and changes
of expression of OsXTH genes. OsXTH5, -19, -20, -24 and -28 genes may play a role in rice peduncle elongation. In addition, interactions among genes may affect PER under drought.
Correlation between ABA content in “mother” tissue and subsequent regeneration ability of Fritillaria imperialis cultured in vitro was investigated. In every experiment regeneration was always most efficient from plant material containing
the lowest amount of free ABA: a leafy stem part, bulbs used for micropropagation in October and those stored two months at
30 °C prior to in vitro culture. However, no direct correlation between the absolute amounts of ABA and percentage of regeneration was found.
The purpose of the study was to examine water stress-induced changes in the ABA and proline contents in roots and leaves of
a potentially more resistant wild accession of Hordeum spontaneum and the modern cultivar Maresi (Hordeum vulgare). Leaves of H. spontaneum had higher contents of constitutive ABA and proline in comparison to those of ‘Maresi’. A moderate water deficit resulted
only in root dehydration, which was higher in ‘Maresi’. Increases of water deficit in roots coincided with an increase of
ABA content in roots, followed by that in leaves. The level of proline increased only in leaves and only in the case of H. spontaneum. Under conditions of severe water stress, the root dehydration levels were similar in the both genotypes, whereas leaf dehydration
was higher in ‘Maresi’. H. spontaneum, as compared to ‘Maresi’ showed an earlier increase of ABA content in the roots and accumulated more ABA in the leaves. Free
proline levels in the roots increased in both genotypes but H. spontaneum exhibited a 2-fold higher proline accumulation than ‘Maresi’. In H. spontaneum the accumulation of proline in the leaves occurred noticeably earlier and to a higher extent than in ‘Maresi’. A possible
connection of these modifications with water stress resistance of the investigated genotypes is discussed in this paper.
The aim of this study was to determine the changes in the abscisic acid (ABA) content in tomato leaves infested by the carmine spider mite (CSM) (Tetranychus cinnabarinus Boidsuval) and in leaves that were mechanically injured. It was also investigated whether signalling from stressed to non-stressed organs occurred.
Tomato plants (Lycopersicon esculentum Mill.) cvs. Romatos and Slonka (with various susceptibility to CSM) were stressed at the stage of first cluster flowering by either CSM feeding (72 hours) or by mechanical puncturing simulated feeding injury by CSM (18 hours).
It was found that under control condition the level of ABA differed significantly between cultivars, being always higher in plants of the susceptible cv. Romatos.
In response to CSM feeding, the content of ABA in infested organs of the more tolerant plant (cv. Slonka) increased by 95 % but in the susceptible one by 11 % only. ABA content in the organs non-stressed by CSM feeding either increased (Slonka cv.) or decreased (Romatos cv.).
In response to mechanical wounding, ABA content in directly injured organs increased but to a lower degree (49 %) and only in Slonka cv.. The same was true for ABA content in non-injured organs of damaged plants of this cultivar. Observed changes in ABA level in non-stressed organs are probably the results of signalling from stressed organs. Plant response measured by changes in ABA level to the stress generated by CSM feeding, was much stronger than merely by mechanical injury.
The experiments were performed to check the effects of exogenous ABA and gibberellin on photosynthetic apparatus and leaf
resistance to freezing. In the experiment, two cultivars (winter and spring) of oilseed rape were used in the experiment.
Discs, cut out from leaves of cold acclimated plants grown at 12 and 20 °C at similar PPFD levels, were immersed for 72 hours
in growth regulator solutions. Some of discs were additionally subjected to high radiation. Independently on cultivar studied,
the effects of growth regulator treatments were significant only in leaves developed at 20 °C. ABA treatment increased frost
resistance, promoted photosynthetic activity measured in cold and inhibited expansion of leaf-disc area, whereas GA3 evoked opposite effects. The treatment with growth regulators particularly affected the resistance of photosynthetic apparatus
to high light. In this case ABA treatment decreased, whereas GA3 increased photoinhibition of PSII. The outcomes may suggest that in the ABA-treated plants PSII is better protected against
photoinduced inactivation both by the increase in effectiveness of photosynthetic dark reactions at high light/low temperature
conditions, increased energy dissipation in xantophyll cycle and enhanced accumulation of anthocyanins. GA3 treatment may affect the resistance to photoinhibition directly via decrease in anthocyanins contents and indirectly through
increase of elongation growth rate in the tissue.
Seedlings of two barley genotypes (‘Maresi’ and wild form of Hordeum spontaneum) were treated with jasmonic acid (JA 5 µM and 15 µM) for 24 h, and then subjected to water stress (PEG 6000 solution of −
1.5 MPa). JA caused an increase in the content of ABA but not in that of proline and spermidine in the two studied genotypes.
The effect of the treatment did not depend on the applied JA concentration. The pre-stress treatment with JA changed plant
response to water deficit with regard to membrane injury. Treatment with a lower JA concentration (5 µM) caused a substantial
reduction of the stress-induced membrane damage in the both genotypes. A higher JA concentration (15 µM) caused the reduction
of membrane injury only in H. spontaneum and was ineffective in ‘Maresi’. JA had no influence on the leaf water status in water-stressed plants. A possible role of
JA in leaf ABA accumulation and alleviation of cell membrane injury under water deficit is discussed.