Resumo -O objetivo deste trabalho foi verificar o efeito da aplicação da poliamina putrescina no acúmulo de prolina e no crescimento inicial de plântulas de guandu cultivadas sob estresse hídrico ou salino, e avaliar se esta poliamina pode ser usada como atenuadora desses estresses. Sementes de duas cultivares de guandu, BRS Mandarim e Caqui, foram germinadas em caixas gerbox forradas com papel de filtro umedecido com 0,0, -0,2, -0,3, -0,4, -0,5 MPa de PEG 6000 ou 0, 20, 40, 60, 80 e 120 mmol L -1 de NaCl, na ausência (0 mmol L -1 ) ou na presença (0,5 mmol L -1 ) de putrescina. Utilizou-se o delineamento inteiramente casualizado, em arranjo fatorial 2x5x2 e 2x6x2 (duas cultivares, cinco níveis de deficiência hídrica ou seis níveis de estresse salino, e presença ou ausência de putrescina), com quatro repetições. O crescimento das plântulas é acentuadamente reduzido pelas condições de restrição hídrica e salinidade. A putrescina exógena incrementa, sob ambos os estresses, os teores de prolina nas plântulas de guandu, especialmente na cultivar BRS Mandarin, e atenua os efeitos da deficiência hídrica moderada nas cultivares estudadas. Os estresses de restrição hídrica e de salinidade causam acúmulo de prolina na parte aérea e nas raízes de ambas as cultivares. A prolina pode ser considerada um bom indicador bioquímico e fisiológico desses estresses em plântulas de guandu.Termos para indexação: Cajanus cajan, indicador bioquímico, poliamina, restrição hídrica, salinidade, solutos compatíveis.Growth and proline content in pigeon pea seedlings subjected to osmotic stress and to exogenous putrescine Abstract -The objective of this work was to verify the effect of the application of the polyamine putrescine on the accumulation of proline and on the early seedling growth of pigeon pea subjected to water or salt stress, and to evaluate whether this polyamine can be used to alleviate these stresses. Seeds of two cultivars of pigeon pea, BRS Mandarim and Caqui, were germinated in gerbox boxes lined with filter papers soaked with 0.0, -0.2, -0.3, -0.4, -0.5 MPa PEG 6000 or 0, 20, 40, 60, 80, and 120 mmol L -1 NaCl, in the absence (0 mmol L -1 ) or presence (0.5 mmol L -1 ) of putrescine. A completely randomized design was used, in a 2x5x2 and 2x6x2 factorial arrangement (two cultivars, five levels of drought or six levels of salt stress, and presence or absence of putrescine), with four replicates. Seedling growth is highly reduced by water restriction and salinity conditions. Exogenous putrescine increases, under both stresses, the proline contents in pigeon pea seedlings, especially in the cultivar BRS Mandarin, and alleviates the effects of moderate water deficiency on the studied cultivars. Water restriction and salinity stresses cause accumulation of proline content in shoots and roots of both cultivars. Proline can be considered a good biochemical and physiological indicator of these stresses in pigeon pea seedlings.Index terms: Cajanus cajan, biochemical indicator, polyamine, water restriction, salinity, compatible so...

Plants are sessile organisms that must perceive and respond to various environmental constraints throughout their life cycle. Among these constraints, drought stress has become the main limiting factor to crop production around the world. Water deprivation is perceived primarily by the roots, which efficiently signal the shoot to trigger drought responses in order to maximize a plant's ability to survive. In this study, the tomato (Solanum lycopersicum L.) mutant procera (pro), with a constitutive response to gibberellin (GA), and its near isogenic line cv. Micro-Tom (MT), were used in reciprocal grafting under well-watered and water stress conditions to evaluate the role of GA signaling in root-to-shoot communication during drought stress. Growth, oxidative stress, gene expression, water relations and hormonal content were measured in order to provide insights into GA-mediated adjustments to water stress. All graft combinations with pro (i.e. pro/pro, MT/pro and pro/MT) prevented the reduction of growth under stress conditions without a reduction in oxidative stress. The increase of oxidative stress was followed by upregulation of SlDREB2, a drought-tolerance related gene, in all drought-stressed plants. Scions harboring the pro mutation tended to increase the abscisic acid (ABA) content, independent of the rootstock. Moreover, the GA sensitivity of the rootstock modulated stomatal conductance and water use efficiency under drought stress, indicating GA and ABA crosstalk in the adjustment of growth and water economy.

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The efficiency of silicon (Si) foliar spraying in sorghum plants can be increased with new sources that may enhance the uptake of the beneficial element with reflexes in physiology. This study investigated the effect of foliar application of Si on different sources of absorption, gas exchange, and growth in sorghum plants, based on the hypothesis that there is a differential response to specific sources and concentrations of Si. An experiment was conducted in a completely randomized design with three replicates (in triplicate). The treatments consisted of five Si sources (nanosilica, silicic acid, stabilized sodium, potassium silicate, and potassium silicate) and four concentrations of Si (0, 0.5, 1.0, and 1.5 g L −1 of Si). Foliar spraying of Si on sorghum plants was effective at increasing the absorption of the beneficial element and the gas exchange of the plant. Nanosilica stood out as an alternative source of Si, and a promising option for foliar spraying in sorghum crops, as it promoted high uptake of the element by the plant. This source also promoted a high photosynthetic rate for both potassium silicate and alkaline silicate. In this study, spraying of 0.88 g L −1 (Si-alkali) and 0.84 g L −1 (Si-potassium) on sorghum at the phenological stages V 4 and V 8 (four and eight fully expanded leaves respectively) and R 1 (beginning of flowering) was promising because it increased plant growth, reduced water loss through transpiration, and had a positive impact on gas exchange.

Potassium contained in sugarcane straw quickly returns to the soil in a form readily available to crops. Thus, the objective of this study was to evaluate the effect of potassium on the nutritional status and grain yield of peanutscultivated in succession with sugarcane harvested without burning. The experiment was installed in Jaboticabal, São Paulo, Brazil, in Dystrophic Red Latosolcultivated with the peanut crop, variety Runner IAC 886. The treatments consisted of the application of 30, 60, 90 and 120 kg ha-1 of K 2 O and a control (no potassium). The experimental design adopted consisted of randomized blocks with five replications. Parameters evaluated were height, diameter, number of leaves, nutritional status for potassium and grain yield. Potassium resulted in a significant increase in the number of leaves and height, K contents (50-70 g kg-1) and grain yield, obtaining 2790 kg ha-1 at a dose of 120 kg ha-1. The sugarcane straw alone is not sufficient to meet the nutritional needs of peanuts planted in succession with sugarcane, where application of potassium fertilizer is necessary to obtain high yields.Potassium fertilization improved the nutritional status and was reflected in the increased production of grains of peanuts grown in rotation with sugarcane, especially at the dose of 120 kg ha-1 K 2 O.

The hypothesis that application of exogenous glycine betaine (GB EX ) may attenuate the effects of mild water deficit in leaf gas exchange and lipid peroxidation in Carapa guianensis was examined. For this reason, 110-d old plants were sprayed with 0, 25, and 50 mM GB EX and then subjected to two watering regimes. In the first, irrigation was continuously performed to maintain the soil near to field capacity (watered plants). In the second, irrigation was withheld and water deficit resulted from progressive evapotranspiration (water-stressed plants). Treatment comparisons were assessed when predawn leaflet water potential (Ψ pd ) of stressed plants reached -1.28 ± 0.34 MPa. Regardless of the watering regime, significant (P<0.05) increases in foliar glycine betaine (GB Leaf ) concentration were observed in response to increasing GB EX ; however, such increases were more expressive in stressed plants. The net photosynthetic rate, stomatal conductance to water vapor, and intercellular to ambient CO 2 concentration ratio were significantly lower in water-stressed plants independently of GB EX concentration sprayed on leaves. The application of 25 and 50 mM GB EX caused significant (P<0.05) increases in ascorbate peroxidase (APX) activity in stressed plants, while significant (P<0.05) increases in catalase activity was observed just in the stressed plants treated with 50 mM GB EX . Malondialdehyde concentrations did not differ between watered and stressed plants regardless of GB EX concentration. In conclusion, C. guianensis was able to incorporate GB EX through their leaves and the resulting increases in GB Leaf attenuated lipid peroxidation in stressed plants through positive modulation of APX and CAT activities.

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The tomato (Solanum lycopersicum L.) cultivar Micro‐Tom (MT) is widely used in physiological studies, but the effects of nitrate ( NO3 - ) and ammonium ( NH4 + ) ratios ( NO3 - : NH4 + ratios) and, in particular, the effects of the accompanying ions in NH4 + sources are unknown. To determine whether the accompanying ions in NH4 + sources influence NH4 + toxicity, the effects of NO3 - : NH4 + ratios on the physiology, electrolyte leakage index, nutrition, and dry weight were studied using hydroponics. The NH4 + sources were ammonium chloride (NH4Cl) or ammonium sulfate [(NH4)2SO4], and five NO3 - : NH4 + ratios were used: 100 : 0, 75 : 25, 50 : 50, 25 : 75, and 0 : 100. The NO3 - source was calcium nitrate [Ca(NO3)2], and the nitrogen (N) concentration was 15 mmol L−1. The results indicate that NH4Cl or (NH4)2SO4 can be used in studies on NH4 + toxicity because the accompanying ions did not influence the tomato plants. In addition, NO3 - : NH4 + ratios of 100 : 0 and 75 : 25 resulted in the highest dry weight of tomato plants, whereas ratios of 25 : 75 or 0 : 100 were toxic.