Physiological characterization of grapevine rootstocks grown in soil with increasing zinc doses/Caracterizacao fisiologica de porta-enxertos de videira cultivados em solo com doses crescentes de zinco

This study aimed to evaluate the performance of grapevine rootstocks under increasing levels of Zn in the soil and to identify physiological variables that can be used as indicators of excess of Zn in the soil. The rootstocks SO4, Paulsen1103, IAC572, IAC313 and 420A were grown in pots containing soil, which received Zn doses of 0, 20, 40, 80 or 160 mg [kg.sup.-1] of soil. Dry matter (DM), Zn content in shoots and roots, chlorophyll index, initial fluorescence ([F.sub.o]), maximum fluorescence ([F.sub.m]), maximum quantum yield of photosystem II ([F.sub.v]/[F.sub.m]), effective quantum yield of photosystem II (Y-II) and non-photochemical quenching (NPQ) were evaluated. The increase of Zn levels in the soil decreased DM in all rootstocks, and IAC572 was superior to the others. The variation in the indices of chlorophyll a and b had little expression in relation the soil Zn levels, but allowed identifying that the rootstocks Paulsen 1103, 420A and SO4 are sensitive to Zn toxicity and that IAC572 and IAC313 were not sensitive to the tested levels. Fluorescence analysis showed a negative effect of Zn contents on the variables [F.sub.o], [F.sub.m], Y-II and NPQ in all rootstocks, which proved to be good indicators of Zn phytotoxicity. Key words: heavy metal toxicity chlorophyll fluorescence Vitis spp. Objetivou-se, neste trabalho, avaliar o crescimento de porta-enxertos (PEs) de videira cultivados em niveis crescentes de Zn no solo e identificar variaveis fisiologicas que possam ser indicadoras do excesso de Zn no solo. Os PEs SO4, Paulsen1103, IAC572, IAC313 e 420A foram cultivados em vasos contendo solo e submetidos a adicao de 0, 20, 40, 80 e 160 mg [kg.sup.-1] de Zn. Avaliaram-se a materia seca (MS), o teor de Zn na parte aerea e raizes, o indice de clorofila, a fluorescencia minima ([F.sub.o]), a fluorescencia maxima ([F.sub.m]), o rendimento quantico maximo do fotossistema II ([F.sub.v]/[F.sub.m]), o rendimento quantico efetivo (Y-II) e a dissipacao nao fotoquimica (NPQ). O aumento da concentracao de Zn no solo reduziu a MS em todos os PEs sendo que o IAC572 foi superior aos demais. A variacao dos indices de clorofilas a e b foi pouco expressiva em relacao aos niveis de Zn no solo mas permitiu identificar que o Paulsen 1103, 420A e SO4 sao sensiveis a toxicidade de Zn e que o IAC572 e IAC313 nao apresentaram sensibilidade nos niveis testados. Com a analise de fluorescencia observou-se que o teor de Zn interfere negativamente sobre as variaveis [F.sub.o],