Claudiana Moura dos Santos

Water deficit is the main limiting factor constraining sugarcane productivity, and its impact is expected to increase due to climate changes. During prolonged drought periods, most plants become extremely vulnerable to ROS accumulation, which can severely damage their photosynthetic apparatus. The PetC gene, encoding a Rieske FeS protein (ISP), has been shown to regulate the electron transport chain and protect photosystems (PSs) under drought conditions in some plant species. In sugarcane, transcriptome analysis revealed that ScPetC is repressed during drought stress in the field. In this study, we have overexpressed ScPetC in tobacco plants and evaluated its role in water-deficit tolerance. Our results indicate that the ScPetC protein structure is conserved when compared to other species. ScPetC overexpression reduced the negative impact of water deficit on plant development. This effect was associated with a positive impact on ScPetC quantum efficiency and the electron transport rate of PSII, the photosynthetic rate, and water use efficiency. The total chlorophyll content under water deficit was higher in plants overexpressing ScPetC, and this was correlated with less chlorophyll degradation from oxidative damage. Together, these results demonstrate that ScPetC confers tolerance to water deficit and oxidative stresses, making it a candidate gene for crop improvement.

Drought stress is the main limiting factor for the yield of soybean crop in the world. Alternatives to minimize the impacts of water deficit on plants involve the application of plant bioregulators, among which Brassinosteroids stand out. In this study, nodulated soybean plants were used to investigate the ability of the 24‐epibrassinolide (EBR) bioregulator to reduce the damage caused to physiological mechanisms, growth and yield, after application in the vegetative stage of soybean plants, subjected to drought stress and rehydration. Application of EBR in plants subjected to drought stress promoted better performance in the rates of transpiration, photosynthesis and instantaneous water use efficiency compared to plants without EBR. The lowest reductions in relative water content and leaf water potential were recorded in stressed soybean plants treated with EBR. Plants under drought stress treated with EBR showed increase in the effective photochemical efficiency of PSII. In addition, soybean plants that received EBR application showed lower oxidative damage to cell membranes. The positive effect of EBR remained after soybean rehydration. Plants treated with EBR showed better recovery with greater plant height, leaf area, lower number of aborted grains, in addition to an increase in stem (37.2%), root (62.8%), leaf (51.8%) dry matter and 1000 seed weight (33%) compared to plants without EBR. This information suggests that EBR not only mitigated the deleterious effect of drought stress but also improved plant growth and yield post‐stress.

Drought is one of the major climatic factors that reduce crop yields in cultivated areas around the world, and studies on physiological responses may help in the selection of drought tolerant genotypes. Thus, this work aimed to correlate gas exchange, photosynthetic efficiency, carbon isotope discrimination (Δ¹³C) and antioxidant activity in sugarcane varieties submitted to water stress under field conditions. Six sugarcane varieties were submitted to drought stress in three development stages: tillering, intense growth and ripening. In all varieties, the photosynthetic apparatus was severely affected by drought, with a reduction in photosynthetic rate and chlorophyll content. During the tillering stage, reductions in gas exchange and increase in Δ¹³C and bundle sheath leakiness (φ) were observed. In the intense growth stage, water stress caused increases in leaf temperature, intrinsic water use efficiency, antioxidant enzyme activity and lipid peroxidation, and reductions in stomatal conductance and transpiration in the RB72454, RB855113 and RB855536 varieties. However, the RB92579 variety maintained a better physiological homeostasis at all development stages and presented higher stalks yielding when submitted to drought. This work suggests that screen sugarcane genotype to drought stress should be performed during the intense growth stage, when plants are more sensitive to drought conditions.

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 MOURA^{2   1}Departamento de Produção e Melhoramento Vegetal - Faculdade de Ciências Agronômicas - UNESP/Botucatu (SP). marcelosilva@fca.unesp.br ²Programa de Pós-graduação em Agricultura - Faculdade de Ciências Agronômicas - UNESP/Botucatu, SP. marcel_agro@yahoo.com.br; andressa_rhein@yahoo.com.br; renats_9@yahoo.com.br; claudianamourabio@yahoo.com.br; paulacarol4@yahoo.com.br 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 (g_s), 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 g_s 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, g_s, 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

VARIÁVEIS MORFOLÓGICAS DA CANA-DE-AÇÚCAR EM FUNÇÃO DO REGIME HÍDRICO DURANTE O DESENVOLVIMENTO INICIAL     LUCAS ALMEIDA DE HOLANDA¹; CLAUDIANA MOURA SANTOS²; GIVALDO D. SAMPAIO NETO³; ANTÔNIO DE PÁDUA SOUSA⁴ E MARCELO DE ALMEIDA SILVA^{5   1}Doutorando em Agronomia (Agricultura), Dpto. de Produção e Melhoramento Vegetal – Faculdade de Ciências Agronômicas –UNESP/Botucatu. lucas_holanda_@hotmail.com ²Pós doutoranda, Instituto de Biologia, Dpto de Genética, Evolução e Bioagentes – UNICAMP. claudianamourabio@yahoo.com.br ³Prof. MSc. Instituto Federal de educação, ciência e tecnologia do Mato Grosso – Campus Confresa. givaldosampaio@bol.com.br ⁴Prof. Doutor. Dpto. de Engenharia Rural - Faculdade de Ciências Agronômicas –UNESP/Botucatu. padua@fca.unesp.br ⁵Prof. Doutor. Dpto. de Produção e Melhoramento Vegetal – Faculdade de Ciências Agronômicas –UNESP/Botucatu. marcelosilva@fca.unesp.br   1 RESUMO   O déficit hídrico está entre os fatores que mais limitam o crescimento e a produtividade agrícola. Mesmo a cana-de-açúcar sendo uma cultura com tolerância moderada à seca, apresenta grandes perdas de produtividade sob esse fator abiótico. Por isso, a seleção de genótipos tolerantes ao déficit hídrico pode representar uma alternativa para diminuir a quantidade de água utilizada na irrigação. Esse trabalho foi desenvolvido com o objetivo de conhecer o desempenho de quatro cultivares de cana-de-açúcar durante o desenvolvimento inicial sob condições de deficiência hídrica, por meio de variáveis morfológicas, visando auxiliar na seleção de genótipos mais tolerantes à seca. O experimento foi conduzido em casa de vegetação, no Departamento de Engenharia Rural da Faculdade de Ciências Agronômicas – UNESP/Botucatu - SP, no período entre 26/11/2010 e 05/04/2011. Foram avaliadas quatro cultivares de cana-de-açúcar (RB855453, RB92579, RB965902 e RB965917) em um tratamento controle (100% da capacidade de campo) e com déficit hídrico (50% da capacidade de campo). As avaliações foram feitas aos 0, 28 e 63 dias após a aplicação do tratamento. Foram avaliados altura da planta; área foliar; comprimento da folha; largura da folha; número de folhas verdes; matéria seca da parte aérea e das raízes. As cultivares RB855453 e RB92579 produziram mais matéria seca da parte aérea e das raízes no tratamento sob déficit hídrico, podendo ser consideradas tolerantes. As cultivares RB965902 e RB965917 tiveram menor produção de matéria seca, sendo consideradas suscetíveis.   Palavras chave: Cultivar, seca, características morfológicas, Saccharum spp, deficiência hídrica.     HOLANDA, L., A.; SANTOS, C., M.; SAMPAIO NETO, G., D.; SOUSA, A., P.; SILVA, M., A. MORPHOLOGICAL VARIABLES OF SUGAR CANE AS A FUNCTION OF THE WATER REGIME DURING  INITIAL DEVELOPMENT   2 ABSTRACT   Water deficit is one of the factors which most limit agriculture yield and growth. Although sugar cane has moderate tolerance to drought, it presents high yield losses under the influence of this abiotic factor. Based on this fact, selection of genotypes tolerant to water stress may represent an alternative for decreasing the amount of water used for irrigation, while keeping or increasing yield. This study was performed in order to evaluate the performance of four sugarcane cultivars during initial development under water stress conditions, by means of morphological variables to select more tolerant genotypes to drought. The experiment was carried out in a greenhouse at the Department of Rural Engineering, College of Agricultural Sciences - UNESP/Botucatu – SP, from November 26th 2010 to April 5th 2011. A total of four sugar cane cultivars were evaluated (RB855453, RB92579, RB965902 and RB965917) under two treatments as follows: control (100% field capacity) and water stress (50% field capacity). Evaluations were performed at 0, 28 and 63 days after treatment application. The following morphological variables were analyzed: plant height, leaf area, leaf length, leaf width, number of green leaves, shoot and root dry matter. The RB855453 and RB92579 cultivars produced more shoot and root dry matter under water stress treatment, while the RB965902 and RB965917 cultivars had lower shoot and root dry matter production under the same conditions. Therefore, the RB855453 and RB 92579 cultivars can be considered tolerant while the RB965902 and RB965917 cultivars can be considered susceptible. Keywords: cultivar, drought, morphological characteristics, Saccharum spp, water stress.