Características Morfofisiológicas E Produtividade De Cana-De-Açúcar Variam De Acordo Com a Cultivar E O Regime Hídrico

Abstract

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). marcelosilva@fca.unesp.br2Programa 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 (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

Inter‐relationship between photosynthetic efficiency, Δ13C, antioxidant activity and sugarcane yield under drought stress in field conditions

“…On the other hand, RB72454, RB855113 and RB855536 varieties presented lower yield under drought stress. Similar results were found in drought‐sensitive sugarcane (Begum & Islam, ; Silva et al, ; Silva et al, ).…”

“…Among the analysed varieties, the RB72454 and RB855536 varieties presented greater reductions in stomatal conductance and transpiration, which may suggest greater sensitivity to drought stress. Different studies on sugarcane reported that greater stomatal closures and reduced transpiration were found in varieties considered more sensitive to drought stress in greenhouse experiments (Machado et al, ; Silva et al, ; Zhao, Glaz, & Comstock, ) and in the field conditions (Endres, Silva, Ferreira, & Barbosa, ; Silva & Costa, ; Silva et al, ).…”

Water potential and gas exchanges in sugarcane irrigated with saline waters

“…At 229 DAP, the RB867515 variety, which is known as tolerant to water stress (Silva et al, 2015), exhibited a mechanism of adaptation to saline stress, evidenced at 229 DAP, because even with reduced stomatal conductance (Figure 1), it was able to maintain photosynthetic rates similar to those of plants with 140 DAP (Figure 3), the moment in which stomatal conductance was higher. Studies conducted by Reis & Campostrini (2008) demonstrate that the photosynthetic rate can be related to stomatal movement.…”

Morphological changes recorded in different phenophases of sugarcane plants subjected to water stress in tropical field conditions

“…At the same time, this variety presented high stalk production, which resulted in high sugar amounts per hectare. Studies on sugarcane plants grown in different regions address that the varieties presenting high purity and Brix rates also have high sucrose concentration in the stalk, fact that leads to high yield in industrial production lines Guo et al, 2014; Silva et al, 2015). Varieties RB92579 and RB867515 recorded the highest stalk yield per hectare, even when they were under water deficit conditions.…”

“…However, these areas are known for being more exposed to water deficit than the traditional producer regions (Guimarães Cardoso et al, 2015). Nowadays, water deficit is one of the major issues faced even by traditional cropping regions; it affects many sugarcane crops worldwide and is the main yield-limiting factor for them (Endres et al, 2010;, Inman-Bamber and Smith, 2012;Gentile et al, 2015;Silva et al, 2015). Besides, stronger drought effects are expected to come due to climate changes and to increased water scarcity, which may further worsen the problem (Zhao and Li, 2015).…”