Respostas agronômicas, bioquímicas e fisiológicas de variedades de cana-de-açúcar submetidas a estresse hídrico associado à nematoide de galhas.

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

05/03/2012

RESUMO

The objective of the present study was to evaluate 1) the effect of hydric deficiency on growth of sugarcane varieties and implications of Meloidogyne incognita parasitism on plant response, 2) hydric relations and gaseous change in sugarcane varieties under both nematode parasitism and hydric deficit, 3) concentration of photosynthetic pigments and organic solutes formed in sugarcane plants under hydric deficit and nematode parasitism. Sugarcane seedlings were inoculated with 30,000 eggs of M. incognita and five days after inoculation, treatments were differentiated in completely randomized design in a 3 (sugarcane varieties RB72454, RB867515 e RB92579) ×2 (hydric treatment 100% CP and 40% CP) ×2 (inoculum level with and without nematode) factorial arrangement. Evaluations were carried out until 45 days after differentiation (DAD). Hydric suppress, besides influence number of leaves and plant height, affected stalk diameter from 14 DAD, being the last one variable that presented lower variation among varieties. RB92579 presented higher number of stalk, differing from the others from 14 DAD. At 40% CP, all varieties had decreased development decreasing root dry matter production, independently of nematode presence. There was no difference in biomass allocation to shoots in parasite and no parasite plants at 100% CP. However, at 40% CP parasite plants decreased 4.86% biomass allocation to shoots. RB867515 stood out presenting root/shoot ratio higher than 50% at 100% CP than 40% CP. Reproduction of M. incognita was significantly higher at 100% CP. inoculated plants had 25% lower development under hydric deficit than at 100% CP as well a 26% reduction under 40% CP when compared to noninoculated ones. RB92579 was the most sensible to hydric suppress. Hydric deficit affected leaf turgescent , being RB867515 the variety that maintained the leaf turgescent. RB92579 presented negative potential at 100% CP. RB867515 was the variety less influenced by hydric deficit (40% CP). Reductions along experimental period on gaseous change, stomata conductance (gs), transpiration (E) and photosynthesis (A) were observed, as well among varieties, hydric treatments and nematode density. Except RB867515, all varieties presented reduction of conductance in presence of nematode under 40% CP. In the absence of nematode, eta nem ndaRB867515 reached the highest stomata conductance values under 100% CP at 45 DAD. Under 100% CP, varieties with nematode presented higher decrease on plant conductance than under 40% CP in relation to non-inoculated. The CO2 liquid assimilation level was highly affected by hydric supress. In plants without nematode under 100% CP there was difference among all varieties, but RB867515 presented the higher photosynthesis. At 40 DAD, RB867515 showed the highest photosynthetic levels in all treatments. RB72454 presented higher amount of carotene and obtained higher amounts of chlorophyll in all treatments, except under 40% CP with no nematode, while RB867515 presented the highest amount in chlorophyll b content as treatment severity increased. In general, soluble carbohydrates concentration decreased as hydric availability decreased in leaves. In roots, carbohydrate concentration promoted interaction among all variables studied with significant increase in this solute concentration in almost all plants inoculated. There was no difference in amino acid concentration within varieties under 100% CP, but under 40% CP RB72454 showed the lowest amino acid concentration. Proline accumulation was stood out in leaves of plants infected with nematode on RB72454 and RB867515 under 100% CP. Protein concentration in leaves showed that, in general, plants with nematode, independently of hydric availability, presented reduction in proline amount. However, plants either with or without nematode presented decrease in protein amount as hydric availability decreased.

ASSUNTO(S)

biomassa clorofila condutância estomática fotossíntese meloidogyne incognita prolina saccharum ciências agrárias biomass chlorophyll stomatal conductance photosynthese prolin

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