José Vera Bahima’s research while affiliated with National University of La Plata and other places

Many trees of high timber value require canopy cover to become established, and at present, they are only harvested from native rainforests. Other species require high radiation to establish and can be planted in monospecific stands. The main question was whether the canopy generated by a light-demanding rainforest species could protect mid-successional timber species from high radiation and extreme temperatures. We evaluated the establishment of Cabralea canjerana under the canopy of Araucaria angustifolia stands. We related growth to the number of neighbors to determine the best positions to plant C. canjerana. In one stand, we measured environmental and physiological traits, and we determined that the seedling did not suffer light or water stress. Cabralea canjerana plant establishment was successful in stands of different basal areas, and trees reached the highest growth with up to two A. angustifolia neighbors within a 5 m radius. Therefore, the number of neighbors is a tool to choose the planting location to convert even-aged to uneven-aged mixed stands. In this way, valuable native timber species that require canopy protection during the first few years can be planted outside the rainforest. This is the first report of an uneven-aged mixed plantation of two Atlantic forest timber species.

The genus Alternanthera Forssk. (Amaranthaceae) is widely distributed throughout tropical and subtropical areas of the Americas. It includes herbs or suffrutices with opposite leaves, perfect flowers protected by a bract and two bracteoles, with capitate stigma and appendages in the staminal tube (or pseudostaminodes) arranged alternately with the stamen filaments, which bear functionally unilocular anthers. Here, a taxonomic revision of the 31 species of Alternanthera that inhabit the Southern Cone and Bolivia is presented. The name A. piptantha Pedersen is synonymized with A. altacruzensis Suess. Type species are designated for genera Brandesia Mart., Bucholzia Mart., Mogiphanes Mart., Steiremis Raf., and Telanthera R. Br. In addition, lectotypes are designated for Achyranthes porrigens Jacq., Alternanthera mexicana (Schltdl.) Hieron. var. gracilis Suess., A. nodiflora R. Br. var. linearifolia Moq., A. tenella Moq., Gomphrena elongata Willd. ex Roem. & Schult., T. meyeriana Regel & Körn, T. rufa (Mart.) Moq. var. glabrata Seub., and a second-step lectotype for A. denticulata R. Br. Identification keys are included for the differentiation of species, subspecies, and varieties, as well as their morphological descriptions, geographic distribution, habitat, vernacular names, uses, illustrations, nomenclatural notes, and information about the studied specimens.

The management of plantations of the critically endangered species Araucaria angustifolia (Bertol.) Kuntze can be an opportunity to mitigate the loss of local biodiversity and to contribute to wood production and Atlantic Forest conservation. Timber species that require canopy protection can be interplanted to convert monospecific stands in uneven-aged mixed plantations. We evaluated the establishment of Cabralea canjerana (Vell.) Mart under the canopy of A. angustifolia and initial competition in an uneven-aged mixed stand. In a 14-year-old stand we planted C. canjerana seedlings in three plots and other three were maintained as pure A. angustifolia plantation. We measured growth and competition in both species using competition indices and C. canjerana environmental and physiological traits to evaluate its acclimation during establishment. Five years after planting, seedling establishment was successful: plants reached a 9-meter height and 75% survived. A. angustifolia increment in diameter at breast height (DBH) was higher in mixed plots than in pure plots. The highest C. canjerana growth was observed with up to two A. angustifolia neighbours within a 5m radius. In other three A. angustifolia stands of different ages, C. canjerana establishment was successful. According to this evidence, it is possible to convert A. angustifolia even-aged stands to uneven-aged mixed stands with beneficial results for both species. In this way, a valuable native timber species that requires canopy protection during the first years can be planted outside the rainforest. This is the first report of a mixed plantation of two native Atlantic Forest timber species.

Atlantic Forest broad-leaved trees of high timber value require canopy cover to become established. Therefore, at present, they are only harvested from native rainforests. Araucaria angustifolia (Bertol.) Kuntze is the only Atlantic Forest Gymnosperm; it requires high radiation to establish and is planted in monospecific stands. The main question was if the umbrella-shaped open canopy generated by A. angustifolia stands was enough to protect mid-successional timber species. We evaluated the establishment of Cabralea canjerana (Vell.) Mart under the canopy of A. angustifolia stands and we related growth with initial competition. In one stand, we measured environmental and physiological traits to evaluate seedling acclimation. C. canjerana establishment was successful in stands of different basal areas. Seven years after planting, C. canjerana plants reached a 12-meter height and 75% survived; the highest growth was observed with up to two A. angustifolia neighbors within a 5m radius. According to this evidence, it is possible to convert A. angustifolia even-aged stands to uneven-aged mixed stands. In this way, a valuable native timber species that requires canopy protection during the first years can be planted outside the rainforest. This is the first report of an uneven-aged mixed plantation of two Atlantic Forest timber species.

The aim of this work was to characterize the secondary metabolite (SMs) profile of Stemphylium lycopersici, a necrotrophic fungus that causes the disease known as grey leaf spot. We detected twenty-four SMs in cultures of S. lycopercisi within the extracts of 19 isolates. Each of them presented a characteristic unique profile. While highly virulent isolates synthesized a high number of metabolites (15), the low virulent ones synthesized a low number of SMs (2). However, a PCA analysis could not establish the relationship between SMs and virulence. Infectopyrone was the most frequent metabolite produced by the isolates (89%).

Senescence in harvested green organs, such as broccoli inflorescences, is a highly regulated process characterized by a massive degradation of chloroplast components. The dismantling of the chloroplast involves small “senescence-associated vacuoles” (SAVs) with high protease activity. The expression of the senescence associated gene, SAG12 (here BoSAG12), which encodes a senescence associated cysteine protease, correlated with SAVs appearance. One environmental factor that delays senescence is low-intensity visible light. Daily irradiation with pulses of 2 h of low-intensity white light (20–25 μmol m⁻² s⁻¹) is a promising technology to delay postharvest senescence of broccoli stored at room temperature. The aim of this study was to analyze the effects of low-intensity white (W) and red (R) light treatments on some events related to chloroplast dismantling during postharvest senescence of broccoli inflorescences. We detected that chloroplasts number did not change during postharvest senescence. We found that SAVs participate in the dismantling of chloroplasts during the postharvest senescence of broccoli florets. SAVs appearance occurred earlier than visible yellowing. The two light treatments used, i.e. pulses of low-intensity W and R light, delayed chloroplast changes, including chlorophyll degradation and SAVs appearance. The delay of SAVs appearance was accompanied by the delay of BoSAG12 induction in broccoli florets. Regarding protein degradation, not all proteins analyzed were affected equally. The light treatments had greater effect on the retention of thylakoid proteins than on Rubisco and apparently, the effects of light treatment were higher on proteins from PSII (LHCII) than on those from PSI (LHCI and PsaA).

High phenotypic plasticity is an important characteristic that should have a tree species that is going to be used to restore degraded rainforests, as those are stressful and changing environments. Quantifying phenotypic plasticity is necessary to compare species and populations. At least 17 different indexes have been employed to measure phenotypic plasticity and most of them were analyzed in pot experiments. However, no studies that evaluate the degree of coincidence between plasticity indexes were applied in pot and field experiments. The aim of this work is to determine the importance of species acclimation and plasticity to the establishment of planted trees for rainforest restoration. We estimated and compared the plasticity and robustness in plants of Araucaria angustifolia and Cabralea canjerana acclimated to full sun and canopy shade in pots, with the slope of the reaction norm. Then, we described the plasticity in a continuum of coverage gradients in rainforest gaps, with environmentally standardized plasticity index for individual distances (ESPIid). Finally, we analyzed the relationship between plasticity and growth performance. C.canjerana had higher plasticity and robustness than A.angustifolia, both in the pot experiment and in the gap experiment. The light-demanding species had lower plasticity than the intermediate shade-tolerant species. The slope of the reaction norm and the ESPIid gave similar qualitative results in the comparison of the species. In C.canjerana, the trait with higher plasticity in the gaps was specific leaf area, which was the better predictor of height 42-months after planting. On the other hand, the prediction of A.angustifolia growth was better fitted with incident light. Growth in A.angustifolia, a species with low plasticity, can be predicted with environmental variables, while growth in C.canjerana, a species with high plasticity, is better predicted with plant traits. The species with higher plasticity in morpho-physiological traits established in all the microenvironments within the gaps, with high growth rate. Survivor of the species with low plasticity was lower in shaded microenvironments than in the positions with higher radiation and light-limited its growth in the gaps. Knowing the plasticity and acclimation capacity of the native species is crucial to choose the better places to plant trees in rainforest restoration and to enhance performance of the young plants.

Visible light irradiance may be a useful technology to delay postharvest senescence of green vegetables. In this work, we studied the effects of low-intensity white, red and far red light pulses on postharvest senescence of broccoli stored in the dark at 20°C. Daily exposure for 2h to 20-25μmolm⁻² s⁻¹ of white light delayed yellowing and retained chloroplast components (chlorophyll and soluble proteins). The utilized light intensity was insufficient to re-initiated photosynthesis since total sugar content was lower than initials in irradiated florets. Light treatment resulted in a slower loss of sugars in comparison with the untreated samples, but was not affected by light quality. The effects of red light treatment on chlorophyll a and soluble protein degradation were similar to white light, and opposite to far red light. However, these treatments did not delay chlorophyll b degradation, suggesting that phytochromes could be involved in molecular mechanism of chlorophyll a and soluble protein degradation, but not of chlorophyll b.

Las plantaciones mixtas con especies nativas son ambientalmente preferibles a las plantaciones mono-específicas. En rodales mixtos se generan interacciones entre los individuos, que pueden incidir negativa o positivamente sobre su crecimiento o mortalidad. Las mezclas de especies pueden ser coetáneas o disetáneas, estas últimas permiten incorporar especies valiosas que requieren la protección de un dosel. El objetivo del trabajo consistió en evaluar si el dosel de una plantación de Araucaria angustifolia permite el establecimiento de Cabralea canjerana en plantación mixta. A los 6,12 y 18 meses después de la plantación se realizaron mediciones morfo-fisiológicas para determinar la supervivencia, el crecimiento y conocer su estado hídrico y fotosintético. La supervivencia de C. canjerana fue alta, cercana al 80%. La respuesta en crecimiento a las condiciones brindadas por el dosel fue positiva tanto en altura como en DAC y no estuvo asociada a los niveles de PAR. La conductancia estomática, como medida de la transpiración, correlacionó de forma negativa con la altura de las plantas. La capacidad fotosintética no varió con el PAR ni con la altura. El dosel de A. angustifolia permite el establecimiento y niveles aceptables de crecimiento de C. canjerana al menos en las primeras etapas de vida.

Hierbas anuales o perennes, sufrútices o arbustos. Hojas opuestas, o las superiores alternas, en general 1-3-pinnatisectas, segmentos lineares a ovados, enteros o dentados, glándulas oleíferas subepidérmicas conspicuas. Capítulos radiados, rara vez discoides, pedunculados, terminales, solitarios, en dicasios o cimas corimbiformes o paniculiformes. Involucro cilíndrico o acampanado, filarios 1-seriados, unidos en casi toda su longitud, excepto los ápices, con glándulas oleíferas. Receptáculo plano a cónico, desnudo. Flores marginales 1 (inconspicua)-13, enteras o 2-3-dentadas, amarillas, anaranjadas, blancas o rojizas, bicolores o ausentes. Flores centrales 6-120, tubulosas, 5-dentadas, amarillas, anaranjadas, blancas o rojizas. Aquenios cilíndricos u obpiramidales, a veces comprimidos, costillados o lisos, glabros o pilosos. Papus con 2-5 (-10) escamas 1-seriadas, cortas o largas, o combinadas, libres o unidas, rara vez ausente.