Response of two bean varieties under two different soil water availability conditions. III. variation in total leaf water potential and in its components for the variety Aroana 80.

Abstract

A field trial was conducted in order to study total leaf water potential, osmotic potential and pressure potential for two different stages of growing period of the bean (Phaseolus vulgaris L.) variety Aroana 80 under two different water deficit conditions. This trial was conducted at the Escola Superior de Agricultura "Luiz de Queiroz"/Universidade de São Paulo ESALQ/USP at a latitude of 22.70°S, longitude of 47.63°W and altitude of 586 metros a.s.l. Two different sowing times (time interval of 15 days) were used. When the first plot was at pod formation stage and the second plot at bud formation stage, irrigation was suspended over a 17 day period. During this period the variety Aroana 80 was evaluated for the following parameters leaf water total potential variation (Ψt), matric potential (Ψm), osmotic potential (Ψo) and pressure potential (Ψp), during the day period and part of the night period. The Ψt, Wo and Ψm + Wo potentials were determined by means of the hygrometric thermocouple method and the Ψp and Ψm potentials were determined by equation Ψt = Ψo + Ψp + Ψm. Differences were observed in the medium values of Ψp, Ψo and Ψm when two growing stages were compared: pod formation stage presented higher total leaf water potential under lower deficit conditions. After some days of study, it was observed an increase in the values of Ψp about noon which night be related to the interaction of the environmental factors and the plant. Generally, all component values influenced by atmospheric component variations.