Photosynthetic rates and partitioning of absorbed light energy in photoinhibited leaves

Abstract

Parameters for the evaluation of the effects of photoinhibition on photosynthetic carbon gain were studied in Chenopodium album leaves. The light‐response curve of photosynthetic rate was determined at 36 Pa CO2 partial pressure and fitted by a non‐rectangular hyperbola. Both the initial slope of the curve and the light‐saturated rate decreased in photoinhibited leaves, although the decrease in the latter was small. The convexity of the curve was also smaller in photoinhibited leaves. The capacities of ribulose‐1,5‐bisphosphate carboxylation (Vcmax) and electron transport (Jmax) were estimated from the CO2‐response curves. Vcmax and Jmax decreased similarly with increasing photoinhibition. Energy partitioning in photosystem II (PSII) was estimated using chlorophyll fluorescence parameters. The fraction of energy that was consumed by photochemistry decreased with increasing photoinhibition. However, an increase in inactive PSII, decreasing energy partitioning to active PSII, relaxed the excitation pressure in PSII, and led to a reduction in the fraction of excess energy that was neither consumed by photochemistry nor dissipated as heat.

Effects of soil warming and nitrogen fertilization on leaf physiology of Pinus tabulaeformis seedlings

“…First, from linear regression of the photosynthetic rate on PPFD at 0-200 lmol m -2 s -1 , U, R d , and LCP were obtained as the slope, y-intercept and the x-intercept of these regressions, respectively. Then, a non-rectangular hyperbola was fitted to the whole curve using the U and R d values to obtain P max and h (Hikosaka et al 2004). Each individual per subplot were randomly selected for determination and the mean value of two individuals for each treatment within the same blocks was used as the replicate for statistical analysis.…”

Growth and physiological responses of Picea asperata seedlings to elevated temperature and to nitrogen fertilization

“…First, from linear regression of the photosynthetic rate on PPFD at 0-200 lmol m -2 s -1 , U, R d and LCP were obtained as the slope, y-intercept and the x-intercept of these regressions, respectively. Then, a nonrectangular hyperbola was fitted to the whole curve using the U and R d values to obtain P max and h (Hikosaka et al 2004). After the measurements, the measured leaves were collected and their projected areas were determined with a scanner and a UTHSCSA ImageTool analysis system.…”

Different growth and physiological responses to experimental warming of two dominant plant species Elymus nutans and Potentilla anserina in an alpine meadow of the eastern Tibetan Plateau

“…First, from the linear regression of the photosynthetic rate on PAR at 0-200 μmol m -2 s -1 , φ, R D , and photosynthetic light compensation point (LCP) were obtained as the slope, y intercept and x intercept of these regressions, respectively. Then, a nonrectangular hyperbola was fitted to the whole curve using the φ and R D values to obtain P max and θ (Hikosaka et al 2004). …”