Gas exchange in litchi under controlled and field conditions

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• 作者：Jer-Chia Chang ; Tzong-Shyan Lin
• 关键词：Litchi chinensis Sonn. ; Photosynthesis ; Stomata conductance ; Quantum yield ; Internal CO₂ concentration ; Transpiration ; Leaf age ; Cropping
• 刊名：Scientia Horticulturae
• 出版年：2007
• 出版时间：20 November 2007
• 年：2007
• 卷：114
• 期：4
• 页码：268-274
• 全文大小：749 K

文摘

Gas exchange of 3-year-old potted ‘73-S-20’ litchi (Litchi chinensis Sonn.) plants were measured under controlled conditions. At 28.8 ± 0.3 °C, dark respiration (R_d) was estimated at 0.6 CO₂ μmol m⁻² s⁻¹, quantum yield (Φ) was 0.024 mol CO₂ mol⁻¹, and light compensation point (PPFD_comp) was 24 μmol m⁻² s⁻¹ photosynthetic photo flux density (PPFD). Maximum net CO₂ assimilation (A_CO2) (6.5–8 μmol m⁻² s⁻¹), stomatal conductance (g_s) (0.07–0.09 mol m⁻² s⁻¹) and transpiration (E) (0.7 mmol m⁻² s⁻¹) were recorded at PPFD >800 μmol m⁻² s⁻¹, leaf temperature (T_L) between 27 and 32 °C, and vapor pressure deficit (VPD) <0.7 kPa. When VPD and T_L simultaneously increased maximum A_CO2 was obtained between 25 and 28 °C. CO₂ compensation point (C_comp) was recorded between 90 and 100 ppm. A_CO2 saturated at external CO₂ concentration >800 ppm. A_CO2 responses to light, and VPD were mainly regulated by stomata. On the other hand, A_CO2 response to internal CO₂ was mainly through leaf photochemistry. At T_L < 28 °C leaf photochemistry dominated A_CO2 responses, while at T_L > 28 °C stomatal regulated A_CO2 responses. Effects of leaf age and location as well as cropping on gas exchange were also studied on 9-year-old in the field trees. Leaf A_CO2, g_s and E on the well-exposed, younger flushes and adjacent to fruit were greater than those on shaded older flushes and woods or those on de-fruiting shoots. Our findings indicated that potential depression of leaf photosynthetic efficiency in litchi might occur due to low temperature in bloom season and early fruit set, as well as due to hot and dry mid-day in early summer.