EFEITO DO TAMANHO DAS SEMENTES SOBRE A EMERGÊNCIA E MORFOFISIOLOGIA DE MUDAS DE MAMA CADELA

O objetivo deste estudo foi avaliar a emergência de plântulas e a morfofisiologia de mudas de mama-cadela (Brosimum gaudichaudii Trécul) produzidas a partir de sementes de diferentes tamanhos. Foram determinadas a porcentagem de emergência de plântulas e as características morfofisiológicas das mudas (altura, diâmetro do colo, índice de robustez, espessura foliar, índice de clorofila, biomassa seca, massa foliar específica - MFE e área foliar total). A emergência iniciou-se após 21 dias da semeadura e atingiu, ao final do experimento, 84% para as sementes pequenas, valor inferior ao das sementes médias e grandes (94 e 90%, respectivamente). Em 60 dias, as mudas apresentavam, em média, 2,53 mm de diâmetro e 12,81 cm de altura. Nos primeiros 30 dias, as mudas formadas a partir de sementes pequenas tinham alturas menores que as demais. O tamanho das sementes não afetou o diâmetro do colo e a espessura das folhas durante o crescimento inicial das mudas, assim como para os parâmetros morfofisiológicos estudados. Ao longo de 120 dias, houve aumento do conteúdo de clorofilas, biomassa seca, área foliar total, exceto para a MFE. O tamanho das sementes afeta a emergência e a altura das mudas de mama-cadela após 30 dias após a emergência. Palavras-chave: Brosimum gaudichaudii; Cerrado; crescimento inicial. Effect of seed size on emergence and mophophysiology of mama-cadela seedlings ABSTRACT: The objective of this study was to evaluate the seedling emergence and morphophysiology of mama-cadela (Brosimum gaudichaudii Trécul) seedlings produced from seeds of different sizes. Seedling emergence percentage and seedling morphophysiological characteristics (height, diameter, slenderness index, leaf thickness, chlorophyll index, dry matter, specific leaf mass - MFE and total leaf area) were determined. The emergence started after 21 days of sowing and reached, at the end of the experiment, 84% for small seeds, lower than the average and large seeds (94 and 90%, respectively). In 60 days, the seedlings had, on average, 2.53 mm in diameter and 12.81 cm in height. In the first 30 days, seedlings formed from small seeds had shorter heights than the others. The seeds size did not affect the diameter and the leaves thickness during the initial growth of the seedlings, as well as for the morphophysiological parameters studied. Over the 120 days, there was an increase in the content of chlorophylls, dry matter, total leaf area, except for MFE. The seeds size affects the emergence and the height at 30 days after mama-cadela seedlings emergence. Keywords: Brosimum gaudichaudii; Brazilian savanna; initial growth.

Effect of herbivory by goats on primary and secondary metabolism of Cocos nucifera L. (Arecaceae) in a semi-arid environment in Brazilian Northeast

The relationship between herbivores and plants has important ecological implications for both organisms and directly affects the plant’s physiological responses, which need to invest in structures and secondary metabolites to overcome the damages. This study aimed to evaluate functional attributes related to the primary and secondary metabolism of Cocos nucifera L. (Arecaceae) submitted to herbivory by goats. Five individuals of C. nucifera were selected in two areas, one with and one without goats. The carbohydrate content, specific leaf mass, and phytochemical screening were obtained, evaluating the presence or absence of saponins, tannins, flavonoids, steroids, alkaloids, and glycosides. The results show that plants under herbivory showed 50% more sugars and a higher specific leaf mass than no-herbivory plants. Also, plants under herbivory showed a higher amount of saponins, steroids, and alkaloids. The production of defense metabolites, which are energetically costly, require the energy supply provided by the carbohydrates produced in photosynthesis; thus, higher levels of sugars were observed in attacked plants. Even under attack, C. nucifera plants allocate resources for biomass production, to increase leaf sclerophylly and hinder herbivory. The investment in saponins, steroids, and alkaloids is related to herbivory, as demonstrated by the analysis of principal components analysis. We conclude that herbivory by goats activates defense responses in C. nucifera plants, making them allocate sugars to produce secondary metabolites.

Biomass growth and development in air-cured burley and flue-cured virginia tobacco varieties

Research on the accumulation and partitioning of biomass in the tobacco cycle is scarce, particularly those comparing different varieties. The objective of this work was to study the partition of biomass in air-cured burley - ACB (BAT2101) and flue-cured virginia - FCV (CSC4704) varieties. In a greenhouse experiment, the two varieties were transplanted into pots containing a mixture of fine sand and substrate (1:1). Samples were taken for a period of 98 days, with 7 day intervals. In each harvest, dry mass and leaf area were measured, and specific leaf mass, leaf area ratio, relative growth rate, net assimilation rate, and root to shoot ratios were estimated. The data showed that carbon partitioning in plants of both varieties is influenced by root growth, which was 50% higher in ACB by the end of the experiment. The higher accumulation of mass in the roots of this variety may be related to the fact that it requires more nitrogen than virginia and, therefore, it could be a mechanism for increased uptake of this element. ACB also had higher specific leaf mass than FCV, which may be related to the body of ACB. This information is important for choosing varieties adapted for field conditions, as well as for the genetic improvement of tobacco. Furthermore, from the point of view of crop management, this knowledge may provide useful information for maximizing leaf growth.

Vehicular emissions effect on the physiology and health status of five tree species in a Bogotá, Colombia urban forest

ABSTRACT. Introduction: Thanks to filtration by foliage, urban trees have a crucial role in air depuration. However, the exposure to pollutants could reduce their health and physiological performance, mainly because of low access to light and clogging of stomata by particulate matter. Objective: The accumulation of particulate matter on leaves (PMAL) and physiological traits of five urban tree species (Croton bogotanus Cuatrec., Eugenia myrtifolia Sims., Ficus soatensis Dugand, Schinus mole L., and Sambucus nigra L.) were quantified in sixty points in Bogotá, with the aims to (1) build a model explaining the PMAL based on traffic variables, (2) establishing the effect of vehicle pollution on physiological and phytosanitary variables, and (3) to evaluate the susceptibility of seedlings and trees to vehicle pollution. Methods: The physiological parameters: photochemical efficiency, stomatal conductance, chlorophyll content, leaf area, and specific leaf mass were measured and correlated with phytosanitary condition, PMAL and traffic variables: number of lanes, vehicular flow and tree-to-avenue distance. Additionally, tree physiological responses were measured in control, residential streets (RS), low traffic avenues (LTA), and high traffic avenues (HTA), and these last were compared with physiology of seedlings planted by three months in HTA. Results: PMAL was strongly associated with physiological responses. Ficus soatensis and C. bogotanus were the species with the maximum and the minimum PMAL. The exposure to traffic increased the photochemical efficiency and specific leaf mass, which could be related to the enrichment of nitrogen and atmospheric CO2. The stomatal conductance followed a bell pattern of low gas exchange in control sites, high values in RS and LTA, and decreasing again in HTA, which suggests an optimization in CO2 fixation at intermediate levels of pollution and susceptibility to stomatal clogging by extreme vehicle emissions. The chlorophyll a/b ratio, leaf area, and specific leaf mass were significantly related to the severity of leaf symptoms, and S. molle was the species with the healthiest leaves in HTA. Seedlings were more susceptible to pollution than trees, and fruits size and seedlings growth were affected by vehicular pollution. Conclusions: Ficus soatensis optimizes particle filtration and C. bogotanus is ideal for planting in HTA, although only as saplings. By contrast, the fast-growing E. myrtifolia and S. nigra seedlings should not be planted in HTA because of susceptibility of pigment contents, leaf area, and stomatal conductance to pollutants. Finally, because of its persistent high stomatal conductance and its low leaf symptoms, S. molle is the species with the best adaptation to vehicle pollution. A complete analysis of interactions among traffic, physiology, and health will help to improve the urban forestry planning.

Photosynthetic Performance of Invasive Vincetoxicum Species (Apocynaceae)

Knowledge of photosynthetic capacity is crucial for fully understanding a species’ invasive potential and for the development of appropriate control strategies. Although growth and reproductive data are available for the invasive swallowwort vines Vincetoxicum nigrum and V. rossicum, photosynthetic data are wanting. These herbaceous, perennial congeners were introduced from separate European ranges during the late 19th century and became invasive during the following century in the northeastern United States and southeastern Canada. Vincetoxicum nigrum has been observed growing mainly in high light environments, whereas V. rossicum occurs across a wide range of light environments, suggesting niche divergence and that different management strategies might be needed for the two species. In this work, we investigated whether the differing habitat associations of these species is reflected in their photosynthetic capacities and leaf morphology. Photosynthetic parameters and specific leaf mass were determined across a range of light environments represented by four field habitats (common garden, forest edge, old field, and forest understory) and two greenhouse environments (high and low light). In the high-light common garden habitat, V. nigrum achieved 37% higher maximum photosynthetic rates than V. rossicum, but photosynthetic performance of the two species was the same in the forest edge habitat. Additionally, species’ performance was virtually identical in high light, low light, and transitions between high and low light regimes in the greenhouse. Specific leaf mass of V. nigrum was 17% higher in the common garden and 19% higher in the greenhouse compared with V. rossicum. Both invasive Vincetoxicum spp. appear capable of growing within a broad range of light environments and their management should be similar regardless of light environment. Other explanations are required to explain the scarcity of V. nigrum in low light natural areas.

CARACTERÍSTICAS MORFOFISIOLÓGICAS E PRODUTIVIDADE DE CANA-DE-AÇÚCAR VARIAM DE ACORDO COM A CULTIVAR E O REGIME HÍDRICO

CARACTERÍSTICAS MORFOFISIOLÓGICAS E PRODUTIVIDADE DE CANA-DE-AÇÚCAR VARIAM DE ACORDO COM A CULTIVAR E O REGIME HÍDRICO MARCELO DE ALMEIDA SILVA1; MARCEL TOMÁS ARANTES2; ANDRESSA FREITAS DE LIMA RHEIN2; RENATA PASSOS PINCELLI2; CLAUDIANA MOURA DOS SANTOS2 E PAULA CAROLINE SILVA MOURA2 1Departamento de Produção e Melhoramento Vegetal - Faculdade de Ciências Agronômicas - UNESP/Botucatu (SP). [email protected] de Pós-graduação em Agricultura - Faculdade de Ciências Agronômicas - UNESP/Botucatu, SP. [email protected]; [email protected]; [email protected]; [email protected]; [email protected] 1 RESUMO Estudos sobre variáveis morfológicas e fisiológicas são importantes para auxiliar na caracterização e entendimento dos mecanismos de tolerância ao estresse e na escolha de cultivares de melhor desempenho em ambientes contrastantes como o irrigado e o de sequeiro. O presente trabalho teve como objetivo diferenciar cultivares de cana-de-açúcar sob ambiente irrigado e sequeiro, por meio de variáveis morfológicas e fisiológicas e a suas respostas em relação à produtividade. O experimento foi realizado em Jaú-SP com as cultivares RB867515 e RB855536. As variáveis morfológicas analisadas foram comprimento de colmos, número de perfilhos, massa foliar específica (MFE) e índice de área foliar (IAF), e as variáveis fisiológicas foram máxima eficiência fotoquímica do fotossistema II (Fv/Fm), condutância estomática (gs), conteúdo relativo de água (CRA), índice SPAD e conteúdo de clorofila (CC a+b). As avaliações ocorreram aos 60, 120, 180, 240 dias após o corte (DAC) do terceiro ciclo e na última avaliação obteve-se a produtividade de colmos (TCH) e de açúcar (TPH). Os resultados demonstraram que a cultivar RB855536 possui maiores valores das variáveis morfológicas comprimento de colmos e número de perfilhos, e das fisiológicas gs e CC a+b e teve maior TPH sob regime hídrico adequado durante o ciclo de desenvolvimento. Enquanto a cultivar RB867515 produziu mais colmos e açúcar sob regime hídrico de sequeiro e manteve valores mais elevados das variáveis morfológicas número de perfilhos e MFE, e das fisiológicas Fv/Fm, gs, CC a+b e CRA. Portanto, cultivares de cana-de-açúcar com maiores valores de comprimento de colmos, número de perfilhos, condutância estomática e conteúdo de clorofila sob regime hídrico adequado durante o desenvolvimento são mais produtivas, enquanto as cultivares mais produtivas sob regime hídrico de sequeiro mantém valores mais elevados de número de perfilhos, massa foliar específica, máxima eficiência fotoquímica do fotossistema II, condutância estomática, conteúdo de clorofila e conteúdo relativo de água na folha. Palavras-chave: Saccharum spp., irrigação, variedades, deficiência hídrica, produção SILVA, M.A.; ARANTES, M.T.; RHEIN, A.F.L.; PINCELLI, R.P.; SANTOS, C.M.; MOURA, P.C.S.MORPHOPHYSIOLOGICAL TRAITS AND YIELD OF SUGAR CANE VARY ACCORDING TO THE CULTIVAR AND WATER REGIME 2 ABSTRACT Studies on morphological and physiological variables are important to assist in the characterization and understanding of the stress tolerance mechanisms and the choice of cultivars with better performance in contrasting environments, such as, the irrigated and rainfed ones. The study aimed at differentiating cultivars of sugar cane in irrigated and rainfed environments through morphological and physiological variables, and their responses concerning productivity. The experiment was carried out in Jaú-SP using the RB867515 and RB855536 cultivars. The morphological variables were as follows: length of stems, number of tillers, specific leaf mass (SLM) and leaf area index (LAI), and physiological variables: photochemical efficiency of photosystem II (Fv/Fm), stomatal conductance (gs), relative water content (RWC), SPAD index and chlorophyll content (CC a+b). The evaluations were performed at 60, 120, 180, 240 days after cutting (DAC) in the third cycle, and at the last evaluation, stem (TCH) and sugar (TPH) yield were obtained. The results showed that the RB855536 cultivar has higher values of morphological variables, i.e., length of stems and number of tiller, and of physiological variables, i. e., stomatal conductance and chlorophyll content. Also, it had higher sugar yield under appropriate water regime during the development cycle. The RB867515 cultivar produced more stems and sugar under the rainfed water regime, and higher values of morphological variables such as number of tillers and specific leaf mass, and of physiological variables such as chlorophyll fluorescence (Fv/Fm), stomatal conductance, chlorophyll content and relative water content in the leaf. Keywords: Saccharum spp., irrigation, cultivars, water stress, yield

High temperature promotes early senescence in primary leaves of sunflower (Helianthus annuus L.) plants

De la Haba, P., De la Mata, L., Molina, E. and Agüera, E. 2014. High temperature promotes early senescence in primary leaves of sunflower (Helianthus annuus L.) plants. Can. J. Plant Sci. 94: 659–669. High temperature affects numerous biochemical and physiological traits in plants. Primary leaves of sunflower (Helianthus annuus L.) were collected from plants grown under a control temperature (day/night regime of 23/19°C) or a high temperature (day/night regime of 33/29°C) for 16, 22, 28, 32 or 42 d. Leaves of sunflower plants exposed to high temperature exhibited decreased growth, as reflected by lower specific leaf mass and reduced leaf area as compared with controls. A superior decrease in soluble protein content during leaf life span in plants grown at high temperature relative to control plants (70% vs. 45%, respectively) suggests that high temperature promotes soluble protein degradation in leaves. High temperature also reduces net photosynthetic rate (P N) possibly by decreasing the content in photosynthetic pigments and the stomatal conductance (g s). The activity of nitrate reductase and glutamine synthetase decreased while deaminating activity in glutamate dehydrogenase increased in leaves exposed to high temperature. Our results suggest that high temperature induced early senescence in sunflower leaves, probably as a result of an accumulation of soluble sugars and the associated decrease in starch levels. Oxidative damage resulting from increased H2O2 accumulation and a decline in antioxidant activity may have also contributed to accelerated senescence of primary leaves at high temperature.

Assimilation apparatus variability of beech transplants grown in variable light conditions of blue spruce shelter

The paper valuates the differences in the selected characteristics of the assimilation apparatus of beech transplants growing in various light conditions of blue spruce small pole stage in the Jizerské hory Mts. in the Czech Republic. The leaf area, chemical parameters, and photosynthetic capacity measured by the method of chlorophyll fluorescence were established. Light conditions of individual beech trees were determined by means of processing a hemisphere photograph of the crown space. The research revealed a significant trend of decreasing nitrogen content with increasing irradiance of the beech. The foliage of the sheltered beech trees exhibited higher contents of phosphorus and potassium. The average specific leaf mass (SLM) of the beech under crowns was lower (0.303 contrary to 0.499 g/dm² in gap) and the respective variants did not differ in average leaf size. A significantly higher maximum fluorescence and a maximum quantum yield (0.854 contrary to 0.803 in gap) were found under crowns. A significant variance was also observed in the absorption capacity. It follows that the beech showed adaptation to the light conditions defined by its location within the stand of blue spruce.

Morpho-physiological responses of cowpea leaves to salt stress

The effect of salt stress of known intensity and duration on morpho-physiological changes in leaves of different ages from cowpea [Vigna unguiculata (L.) Walp.] plants was studied, aiming for a better understanding of the acclimation process of the whole-plant. Seeds were sown in vermiculite and seedlings were transferred to plastic trays containing aerated nutrient solution, and kept in a greenhouse. When the first trifoliate leaf emerged the seedlings were transplanted into 3 L plastic pots containing aerated nutrient solution. Salt additions started 5 d later, and the salt-treated plants received 25 mmol L-1 per day until reaching a final concentration of 75 mmol L-1. During the experimental period primary leaves and the 1st, 2nd, and 3rd trifoliate leaves were used for measurements of net photosynthesis, leaf area, leaf succulence, specific leaf mass, ions and chlorophyll concentrations. Growth analysis of the whole-plant was performed at the end of the experimental period. Salinity did not affect net photosynthesis, but reduced dry mass production and the number of lateral branches. Leaf concentrations of Na+, Cl-, K+ and P increased in salt-stressed plants, but these responses were dependent upon stress duration and leaf age. The higher concentration of potentially toxic ions (Na+ and Cl-) in older leaves could contribute to the reduced ion accumulation in growing tissues, but the tendency of K and P accumulation in leaves appeared to be the result of reduced re-translocation, i.e., not related to plant acclimation. Salinity also increased the source/sink ratio, leaf succulence, specific leaf mass, and chlorophyll accumulation per unit of leaf area, suggesting that the observed changes could be part of an integrated mechanism of whole-plant acclimation to salt stress.