Trocas gasosas e fluorescência da clorofila a em variedades de cana-de-açúcar submetidas à deficiência hídrica

Abstract

RESUMOO estresse hídrico afeta grande parte da agricultura mundial, razão por que se propôs, através deste trabalho, avaliar o comportamento, em casa-de-vegetação, de quatro variedades de cana-de-açúcar (SP79-1011, RB72454, RB98710 e RB92579) submetidas a déficit hídrico durante a fase inicial de crescimento vegetativo. As plantas foram cultivadas em vasos plásticos contendo 15 kg de solo. O estudo foi um fatorial (4 variedades x 3 níveis de água disponível no solo), em delineamento inteiramente casualizado, com cinco repetições. Os níveis de água no solo foram baseados na capacidade de água disponível (CAD) ficando assim definidos: controle (80 a 100% da CAD), estresse hídrico moderado (40 a 60% da CAD) e estresse hídrico severo (0 a 20% da CAD). A deficiência hídrica provocou reduções significativas na condutância estomática (g s ), transpiração foliar (E), fotosíntese líquida (A) e na eficiênca de uso da água de produção (EUA p ), independente da variedade. As variedades SP79-1011 e RB98710 apresentaram maior sensibilidade estomática, reduzindo g s e E aos 71 dias após início do estresse, mesmo sob condições controle; entretanto, em tais condições A foi pouco afetada, indicando que as plantas são capazes de manter a taxa fotossintética, mesmo com os estômatos parcialmente fechados. O estresse hídrico provocou pouca redução na eficiência fotoquímica potencial das variedades estudadas.Palavras-chave: fotossíntese, condutância estomática, estresse hídrico Gas exchange and chlorophyll a fluorescence of sugarcane varieties submitted to water stress ABSTRACT Water stress affects a great part of the world's agriculture. Thus, this work was conducted to evaluate photosynthetic traits in four varieties of sugarcane (SP79-1011, RB72454, RB98710 and RB92579) submitted to water stress during the early stage of the vegetative period. The plants were cultivated in plastic pots (15 kg of soil). The study was a factorial (4 varieties x 3 levels of soil water content based on available water capacity (AWC)), in a completely randomized design with 5 replications. The levels of water content in the soil were as follows: control (80 to 100% of AWC), moderate water stress (40 to 60% of AWC) and severe water stress (0 to 20% of AWC). Water stress provoked a significant reduction in stomatic condutance (g s ), foliar transpiration (E), net photosynthesis (A) and in the water use efficiency of production (WUE y ), irrespective of varieties. The varieties SP79-1011 and RB98710 showed greater stomatal sensitivity, reducing g s and E by the 71 days after the beginning of the water stress treatments, even in the control. However, under such conditions A was little affected, indicating that the plants are capable to fixing CO 2 with stomata partially closed. Water stress caused a small reduction in the potential photochemical efficiency (F v /F m ratio) in the studied varieties.

Growth and physiological characteristics of the weed false johnsongrass ( Sorghum arundinaceum (Desv.) Stapf)

“…(2010) observed an E value . A similar behavior was observed for the stomatal conductance (gs), in the different phenological phases of S. arundinaceum ( Figure 5C), which also are similar to findings in the literature for sugarcane (Gonçalves at al., 2010) and corn ). The conductance is proportional to the number and size of stomata and their opening diameter, which depend on factors inherent to the genotype and the environment (Brodribb & Holbrook, 2003).…”

Arugula production as a function of irrigation depths and potassium fertilization

“…For both K 1 and K 2 doses, the chlorophyll index decreased always when the water deficit, caused by the application of the lowest irrigation depths, was accentuated. Gonçalves et al (2010) and Jangpromma et al (2010) also observed reduction in the chlorophyll index of plants subjected to water stress, in comparison to plants satisfactorily irrigated. The highest value of chlorophyll was observed in the treatment L 4 K 1 , related to the irrigation depth of 100% ETc and K dose equal to 200 kg ha -1 of K 2 O.…”

Physiological responses to intense water deficit in two genotypes of crambe (Crambe abyssinica Hochst.)

“…Under water deficit, structural and functional alterations of photosynthetic apparatus can be estimated using the chlorophyll a fluorescence (CF) analysis (Stirbet and Govindjee, 2011;Zushi and Matsuzoe, 2017). The CF is a non-destructive, simple, and rapid testing method used to evaluate the functionality of the photosynthetic apparatus under environmental stress (Chen et al, 2015;Gonçalves et al, 2010;Oukarroum et al, 2007). Under water deficit, CF analysis has been used to monitoring and screening tolerance of species, genotypes and lineages to stress (Campos et al, 2014;Gomes et al, 2012;Oukarroum et al, 2009).…”