科研之友
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摘要
leaf water potential is one of the most important factors affecting stomatal functioning. the aim of this study was to assess the effect of variation in diurnal irradiance and vapour pressure deficit on photosynthesis (a), stomatal conductance (gs) and leaf water potential (y) in carapa guianensis (aubl.). data were collected from 07:00 to 17:00 h. photosynthetic rates reached a maximum (2.5 米mol m-2 s-1) at 10:00 h, thereafter declined to a minimum of 1 米mol m-2 s-1 at 16:00 h. stomatal conductance oscillated during the day, from 0.04 mol m-2 s-1 (at midday) to 0.02.mol.m-2.s-1 at the end of the afternoon. leaf water potential was higher early in the morning (-0.3 mpa) and lower (-0.75 mpa) at mid-afternoon (14:30 -15:00 h). after reaching a minimum, y increased up to -0.64 mpa at sunset. photosynthetic rates increased linearly as a function of gs (p %26lt; 0.01). also there was a positive relationship between y and gs (p%26lt; 0.01). photosynthetic rates declined during the day after reaching a peak early in the morning, which makes clear that environmental factors that influence y greatly affect carbon assimilation of c. guianensis.
