Abstract
In this research, we hypothesized that Ormosia arborea (Vell.) Harms seedlings should grow better and achieve greater levels of gas exchange when grown in soils with higher water availability. Thus, this study was developed to assess the metabolic responses of the seedlings to different levels water availability. Irrigation was performed on alternate days, at water holding capacities (WHC) of 25%, 50%, 75%, and 100%. The metabolic responses were analyzed at 15, 50, 85, and 120 days after starting treatments. The O. arborea plants grown in conditions of higher water availability (75% and 100% WHC) had higher leaf water potential and chlorophyll content, in addition to higher values for chlorophyll a fluorescence and gas exchange, than those grown in other conditions. Water deficit caused by low levels of water availability (25% or 50% WHC) reduces leaf water potential, chlorophyll a fluorescence, and gas exchange. As a strategy to tolerate stress, seedlings tend to invest in their antioxidant system, as shown by the high levels of activity of the enzymes Superoxide dismutase (SOD), Peroxidase (POD), and Catalase (CAT). Although the seedlings may be tolerant to cultivation under 50% WHC, the best functioning of the photosynthetic apparatus occurred under WHC of 75%.
Keywords:
Antioxidant enzymes; Chlorophyll a fluorescence; Hydric stress; Photosynthesis
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Source: Authors (2019). In where: Water potential of the leaves - Ψw (A); index of chlorophyll (SPAD) - IC (B); potential quantum efficiency of photosystem II (Fv/Fm) (C); Photosynthetic rate - A (D); transpiration - E (E); water use efficiency - WUE (F) in Ormosia arborea (Vell.) Harms depending on different water retention capacity (WRC) and evaluation times (days).
Source: Authors (2019). In where: Internal CO2 concentration - Ci (A); stomatal conductance - gs (B); carboxylation efficiency of ribulose RUBISCO - A/Ci (C); intrinsic water use efficiency - IWUE (D) in Ormosia arborea (Vell.) Harms depending on different water retention capacity (WRC) and evaluation times (days).
Source: Authors (2019). In where: Enzimatic activity in leaves and roots of superoxide dismutase (SOD leaves and roots) (A, B) and roots (SOD roots) (B); of peroxidase (POD leaves and roots) (C, D); of catalase (CAT leaves and roots) (E, F) in Ormosia arborea (Vell.) Harms depending on different water retention capacity (WRC) and evaluation times (days).