PHYSIOLOGICAL RESPONSES OF THREE WOODY SPECIES SEEDLINGS UNDER WATER STRESS, IN SOIL WITH AND WITHOUT ORGANIC MATTER

摘要

The low availability of water in the soil is one of the limiting factors for the growth and survival of plants. The objective of this study was to evaluate the responses of physiological processes in early growth of guanandi (Calophyllum brasilense Cambess), African mahogany (Khayai vorensis A. Chev) and oiti (Licaniato mentosa Benth Fritsch) over a period of water stress and other of rehydration in the soil with and without addition of organic matter. The study was conducted in a greenhouse and the experimental design was completely randomised into a 3 x 2 x 2 factorial scheme, comprising three species (guanandi, African mahogany, and oiti), two water regimes (with and without water restriction) and two levels of organic fertilisation (with and without the addition of organic matter). Irrigation was suspended for 15 days in half of the plants, while the other half (control) continued to receive daily irrigation, the soil being maintained near field capacity for these plants. At the end of the stress period, the plants were again irrigated for 15 days to determine their recovery. Water restriction reduced leaf water potential and gas exchange in the three species under study, more severely in soil with no addition of organic matter. The addition of this input increased soil water retention and availability to the plants during the suspension of irrigation, reducing the detrimental effects of the stress. During the period of rehydration, there was strong recovery of water status and leaf gas exchange. However recovery was not complete, suggesting that some of the effects caused by stress irreversibly affected cell structures and functions. However, of the species being studied, African mahogany displayed a greater sensitivity to stress, with poorer recovery.