Postharvest quality of Aster ericoides after treatment with silver thiosulphate and sucrose / Qualidade pós-colheita de Aster ericoides após tratamento com tiossulfato de prata e sacarose

ABSTRACT: Aster (Aster ericoides L.) is a flower crop of North American origin, which belongs to the family Asteraceae. This plant presents capitulum-type inflorescences, widely used as cut flowers. In Brazil, it has been grown only recently, but still has a high expansion potential. In floriculture, pulsing and conditioning solutions are often used to extend the vase life of cut flowers. The present study aimed to evaluate the influence of silver thiosulphate (STS) pulsing and sucrose solutions on the postharvest life of A. ericoides stems. The experiment was carried out under a complete randomized design with treatments arranged in a 2x5 factorial scheme. Treatments consisted of flower stems treated with STS pulsing for 30 minutes, combined with four sucrose concentrations (5, 10, 15, and 20%) for six hours, plus a control (without treatment). Each plot contained four replicates of 10 stems, totalizing 400 stems. The following variables were daily: vase life, fresh mass, and relative water content (RWC). For pulsing data, means were compared by the Tukey's test (p≥5%). Yet for sucrose concentrations, means were submitted to a polynomial regression to verify the behavior of variables as a function of concentrations increases. Likewise, each treatment was evaluated for fresh mass and RWC variations over time by a polynomial regression. Results indicated no effect of STS pulsing (2mM) on the vase-life length of aster stems. In contrast, the sucrose solution at 10% extended the vase life of stems by two days, decreased fresh mass loss, and helped maintain water balance in stems.

RESUMO: O áster (Aster ericoides L.) é originário da América do Norte, pertence à família Asteraceae, possui inflorescências do tipo capítulo e é muito usada como flor de corte. No Brasil, sua produção é recente e apresenta grande potencial de expansão. O uso de soluções de "pulsing" e de acondicionamento, em flores de corte, é bastante empregado na floricultura para prolongar o tempo de prateleira. O objetivo do presente estudo foi avaliar a influência do "pulsing" de STS (tiossulfato de prata) e do condicionamento em soluções de sacarose na vida pós-colheita de hastes de A. ericoides. O delineamento experimental foi inteiramente casualizado e os tratamentos foram arranjados em esquema fatorial 2x5, ou seja, com e sem aplicação de "pulsing" com tiossulfato de prata (STS) 2mM por 30 minutos, combinados com quatro concentrações de sacarose: 5, 10, 15 e 20% por 6 horas e tratamento controle; foram 4 repetições e 10 hastes por parcela, perfazendo um total de 400 hastes. Avaliou-se diariamente a vida de vaso, acúmulo de massa fresca e conteúdo relativo de água (CRA) das hastes tratadas. Os dados de "pulsing" (STS) as médias foram comparadas pelo Teste de Tukey a 5% de probabilidade. As médias de sacarose foram submetidas à análise de regressão polinomial a fim de verificar o comportamento das variáveis em função do aumento da concentração de sacarose e para massa fresca e CRA foi realizada regressão polinomial para cada tratamento a fim de verificar o comportamento do tratamento ao longo do tempo. Concluiu-se que tratamento de "pulsing" com tiossulfato de prata (STS) a 2mM por 30 minutos não contribuiu para o aumento da vida de vaso das hastes de áster. O tratamento de condicionamento com 10% de sacarose prolongou a vida de vaso em dois dias, diminuiu a perda de massa fresca e favoreceu o balanço hídrico de hastes de áster.

Respostas fisiológicas de clones de eucalipto cultivados em casa de vegetação sob deficiência hídrica / Physiological responses of eucalyptus clones grown in a greenhouse under water deficit

Os prolongados períodos de seca no Sudoeste da Bahia podem causar prejuízos ao cultivo de eucalipto, que é a principal espécie florestal cultivada nessa região. Com o propósito de se conhecer o desempenho de alguns clones de eucalipto, face às restrições hídricas dessa região, realizou-se um experimento em casa de vegetação, no qual foram avaliadas respostas fisiológicas de quatro clones de eucalipto à baixa disponibilidade de água no solo. Utilizou-se delineamento inteiramente ao acaso, no qual os tratamentos constituíram um arranjo fatorial 4x2 (clones VM01, VCC0865, AEC0144 e AEC0224, sob regimes hídricos irrigado e não irrigado), com quatro repetições e duas plantas por parcela. Mudas com 90 dias de idade foram aclimatadas em casa de vegetação e irrigadas durante 60 dias. Após esse período, suspendeu-se a irrigação para um grupo de plantas, dando início às avaliações de potencial hídrico foliar (Ψw), teor relativo de água (TRA), transpiração (E), condutância estomática (gs), fotossíntese (A) e concentração interna de CO2 (Ci). A deficiência hídrica causou alterações significativas em todas as variáveis avaliadas: Ψw, TRA, E, gs e A sofreram decréscimos, ao passo que Ci aumentou. As reduções em Ψw e TRA não registraram diferenças significativas entre os clones. Em relação a A, essa redução foi menor no clone VM01.

The long dry periods in Bahia Southwest can harm the eucalyptus cultivation, which is the most important forestry specie cultivated in this region. This research aimed to evaluate the physiological responses of eucalyptus clones, grown in a greenhouse under water deficit. The experiment was carried out in a completely randomized design, and the treatments were a factorial 4x2 (VM01, VCC0865, AEC0144 and AEC0224 clones, under irrigated and non irrigated water regimes) with four replications and two plants per plot. The seedlings were 90 days old and the acclimation was carried out in a greenhouse, with irrigation, for 60 days. After the acclimation, irrigation was interrupted to a group of plants, and the following evaluations were started: leaf water potential (Ψw), water relative content (TRA), transpiration (E), stomatal conductance (gs), photosynthesis (A) and CO2 internal concentration (Ci). Significant changes were observed in all variables. There was a decrease in Ψw, TRA, E, gs and A, whereas increased Ci. The Ψw and TRA decreases showed no significant differences among the clones. In relation to A, this decrease was lower in VM01 clone.

Water potential and viability of seeds of Eugenia (Myrtaceae), a tropical tree species, based upon different levels of drying

The aim of the present work was to study the water potential and viability of Eugenia based upon different levels of drying. The seeds showed high water content at shedding and were sensitive to desiccation; however, the level of this sensitivity (water content) varied among the species. Five target drying levels were defined according to the critical levels of hydration. Results showed that water potential seemed to be more reliable than water content. It was hypothesize that the differences in desiccation tolerance, as well as recalcitrance, among the seeds of different species could be related to the maturity level of these seeds during shedding from the mother plant. Consequently, this could be a result of the evolution on how far the maturation process could represent an advantage for the species propagation. This could also mean that Eugenia seeds were dispersed at a maturity stage similar to that observed in immature orthodox seeds.

Pre-treatment of seeds with static magnetic field ameliorates soil water stress in seedlings of maize (Zea mays L.).

The effect of magnetic field (MF) treatments of maize (Zea mays L.) var. Ganga Safed 2 seeds on the growth, leaf water status, photosynthesis and antioxidant enzyme system under soil water stress was investigated under greenhouse conditions. The seeds were exposed to static MFs of 100 and 200 mT for 2 and 1 h, respectively. The treated seeds were sown in sand beds for seven days and transplanted in pots that were maintained at -0.03, -0.2 and -0.4 MPa soil water potentials under greenhouse conditions. MF exposure of seeds significantly enhanced all growth parameters, compared to the control seedlings. The significant increase in root parameters in seedlings from magnetically-exposed seeds resulted in maintenance of better leaf water status in terms of increase in leaf water potential, turgor potential and relative water content. Photosynthesis, stomatal conductance and chlorophyll content increased in plants from treated seeds, compared to control under irrigated and mild stress condition. Leaves from plants of magnetically-treated seeds showed decreased levels of hydrogen peroxide and antioxidant defense system enzymes (peroxidases, catalase and superoxide dismutase) under moisture stress conditions, when compared with untreated controls. Mild stress of -0.2 MPa induced a stimulating effect on functional root parameters, especially in 200 mT treated seedlings which can be exploited profitably for rain fed conditions. Our results suggested that MF treatment (100 mT for 2 h and 200 for 1 h) of maize seeds enhanced the seedling growth, leaf water status, photosynthesis rate and lowered the antioxidant defense system of seedlings under soil water stress. Thus, pre sowing static magnetic field treatment of seeds can be effectively used for improving growth under water stress.

Tolerance to water deficiency between two soybean cultivars: transgenic versus conventional / Tolerância à deficiência hídrica entre dois cultivares de soja: transgênico versus convencional

The main goal of the study was to evaluate the effects on the development and physiological aspects of soybean plants grown under water deficiency at greenhouse conditions, comparing the levels of tolerance to water deficiency between one transgenic and one conventional cultivar, enabling a systematic way to carried out physiological comparisons between soybean cultivars under drought. The study was divided into completely randomized using a factorial 2×2 design, with five replicates. The experimental design included two replenishment levels of daily irrigation (100 percent and 40 percent), applied to the leaves during the V4 developmental stage (fourth trifoliate fully expanded) and two cultivars, 'CD 202' conventional and 'CD 226RR' transgenic. The results showed that both cultivars had similar effects, caused by water deficiency, on dry mass production, but the transgenic cultivar tended to maintain higher biomass allocation in pods, as well as, higher efficiency of leaves to support dry mass production than conventional cultivar in both water conditions. Moreover, the higher maximum CO2 assimilation values and lower membranes damages in the transgenic cultivar under water deficiency showed that the expected higher drought tolerance of the conventional cultivar was not supported by a more accurate physiological investigation.

O principal objetivo do estudo foi avaliar os efeitos sobre o desenvolvimento e aspectos fisiológicos de plantas de soja cultivadas sob deficiência hídrica em condições de casa de vegetação, comparando os níveis de tolerância à deficiência de água entre um cultivar transgênico e um convencional, gerando uma forma sistemática de realizar comparações fisiológicas entre cultivares de soja sob déficit hídrico. O delineamento experimental foi inteiramente casualizado, em esquema fatorial 2×2, com cinco repetições. Os tratamentos hídricos foram dois níveis de reposição de irrigação diária (100 por cento e 40 por cento), aplicados a partir do estádio V4 (quarto trifólio completamente expandido), em dois cultivares ('CD 202' convencional e 'CD 226RR' transgênico). Os resultados evidenciaram que ambos os cultivares tiveram as mesmas respostas na produção de massa seca, mas o cultivar transgênico tendeu a manter maior alocação de biomassa em vagens, assim como maior eficiência da área foliar para a produção de massa seca em ambas as condições de irrigação. Além disso, os maiores valores de assimilação máxima de CO2 e menores danos às membranas no cultivar transgênico, sob deficiência hídrica, mostraram que a maior tolerância à seca esperada do cultivar convencional não foi apoiada por uma investigação fisiológica mais acurada.