Irradiance influences tea leaf (Camellia sinensis L.) photosynthesis and transpiration

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Abstract

Rates of net photosynthesis (PN) and transpiration (E), and leaf temperature (TL) of maintenance leaves of tea under plucking were affected by photosynthetic photon flux densities (PPFD) of 200–2 200 μmol m−2 s−1. PN gradually increased with the increase of PPFD from 200 to 1 200 μmol m−2 s−1 and thereafter sharply declined. Maximum PN was 13.95 μmol m−2 s−1 at 1 200 μmol m−2 s−1 PPFD. There was no significant variation of PN among PPFD at 1 400–1 800 μmol m−2 s−1. Significant drop of PN occurred at 2 000 μmol m−2 s−1. PPFD at 2 200 μmol m−2 s−1 reduced photosynthesis to 6.92 μmol m−2 s−1. PPFD had a strong correlation with TL and E. Both TL and E linearly increased from 200 to 2 200 μmol m−2 s−1 PPFD. TL and E were highly correlated. The optimum TL for maximum PN was 26.0 °C after which PN declined significantly. E had a positive correlation with PN.

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