Eficiência de uso da água em genótipos de cana-de-açúcar submetidos à aplicação de herbicidas

Abstract

RESUMO -Objetivou-se com este trabalho avaliar os efeitos de ametryn e trifloxysulfuronsodium, em aplicações isoladas ou em mistura, sobre as características associadas à eficiência do uso da água em genótipos de cana-de-açúcar. O delineamento experimental foi em blocos casualizados, com quatro repetições, em parcelas subdivididas. As parcelas foram compostas pelos herbicidas ametryn e trifloxysulfuron-sodium e pela mistura formulada de ametryn + trifloxysulfuron-sodium, aplicados aos 65 dias após o plantio, além de uma testemunha sem presença de plantas daninhas; e as subparcelas, pelos genótipos RB72454, RB835486, RB855113, RB867515, RB947520 e SP80-1816. Decorridos 15 dias da aplicação dos herbicidas, foram realizadas as avaliações de condutância estomática de vapores de água (Gs), gradiente entre temperatura da folha e do ar (∆T) e taxa de transpiração (E), sendo calculada ainda a eficiência do uso da água (WUE). Foi determinada também a matéria seca da parte aérea das plantas. O genótipo RB855113 foi o que apresentou maiores danos à eficiência do uso da água e transpiração, sendo, por isso, considerado o mais sensível aos herbicidas ametryn e trifloxysulfuron-sodium, enquanto os genótipos SP80-1816 e RB867515 estiveram entre os mais tolerantes. Condutância estomática, temperatura da folha, transpiração e eficiência de uso da água são características eficientes para identificar danos de herbicidas a plantas cultivadas, principalmente aqueles com efeito sobre a taxa fotossintética. Os genótipos de cana-de-açúcar avaliados diferiram quanto à sensibilidade aos herbicidas aplicados; as variedades SP80-1816 e RB867515 destacaram-se como as menos afetadas pelo ametryn e trifloxysulfuron-sodium, isolados ou em mistura, enquanto RB855113 foi a mais sensível.Palavras-chave: Saccharum spp., uso eficiente da água, mistura herbicida, cultivares de cana-de-açúcar.ABSTRACT -The objective of this study was to evaluate the effects of the herbicides ametryn and trifloxysulfuron-sodium, applied alone or in mixture, on the characteristics associated to water use efficiency in sugarcane varieties under field conditions. The trial was installed in a completely randomized block design with split-plots and four replications. Plots were composed by the herbicides ametryn, trifloxysulfuron-sodium or a commercial mixture of ametryn + trifloxysulfuron-sodium, applied 65 days after planting, plus a control mechanically free of weed infestation; split-plots were composed by sugarcane varieties (RB72454, RB835486, RB855113, RB867515, RB947520 and SP80-1816). Fifteen days after herbicide application, stomatal conductance (Gs), temperature gradient between leaf and air (DT) and transpiration rate (E) were evaluated, and water use efficiency (WUE) was obtained as a function of photosynthesis and transpiration rates. Plant shoots were also collected for dry matter determination. Variety RB855113 presented the greatest damage to water use efficiency and transpiration and was thus considered the most sensitive to ametryn and trifloxysulfuron, ...

Directed-spray application of paraquat and diuron in physic nut plants

“…According to Galon et al (2010), the photosynthetic parameters g s , E and WUE are Directed-spray application of paraquat and diuron in physic ... efficient at identifying herbicide damage to cultivated plants, especially those affecting the photosynthetic apparatus, which indirectly influences the parameters associated with water use. Therefore, it can be inferred that diuron had negative effects on net photosynthesis, probably as a result of damage to the leaf tissue after the production of peroxides in the inhibition of electron flow in OS II, which consequently induced the production of abscisic acid (ABA) and stomatal closure, because these effects reduce stomatal conductance and CO 2 in the inner space of the leaf (Zhang et al 2001;Tironi et al 2010).…”

“…According to Galon et al (2010), because herbicides have different mechanisms of action, they may influence photosynthetic activity directly or indirectly. Thus, the damage caused by plant phytotoxicity can be more efficiently measured from the photosynthetic rate and variables associated with it, such as stomatal conductance, transpiration, internal CO 2 concentration and water use efficiency.…”

Alterações nas características fisiológicas de cultivares de cana-de-açúcar submetida à aplicação de herbicidas

“…Com relação à cana-de-açúcar, no Brasil há poucos estudos que avaliaram o efeito de herbicidas na eficiência do uso da água em genótipos de cana-de-açúcar. Galon et al (2010b), ao trabalharem com vários genóti-pos de cana-de-açúcar, constataram que o RB855113 apresentou a menor eficiência de uso da água quando submetido à aplicação de ametryn e do trifloxysulfuron-sodium.…”

Influência de Brachiaria brizantha nas características fisiológicas relacionadas a fotossíntese e uso eficiente da água em cana-de-açúcar

“…The competitive ability of weeds in capture of environmental resources vary depending on the species present at the area, the population density and the timing of weed emergence in relation to the emergence of the crop (Vidal et al, 2004), as well as the competitive ability native to the crop variety (Galon et al, 2010). The competition between weeds and crops leads to a lower supply of resources for some species -the less efficient in capturing that given resource, causing deficiencies that culminate in changes at physiological parameters related to photosynthesis.…”

“…Whereas the competition with weeds cause physiological changes in crops, it is assumed that the physiological characteristics related to photosynthesis and water use efficiency can be indicators of the level of competition between these species and crops (Concenço et al, 2009;Galon et al, 2010). Therefore, this study aimed to evaluate the interference of populations of Brachiaria brizantha in traits related to photosynthetic activity and water use efficiency of sugarcane varieties RB72454, RB867515 and SP80-1816.…”