Photosynthetic characteristics of Stipa purpurea under irrigation in northern Tibet and its short-term response to temperature and CO2 concentration

doi:10.3724/SP.J.1258.2011.00311

Abstract

Abstract:

Aims Stipa purpurea is a dominant species of alpine grassland in northern Tibet, a region sensitive to climate change. Environmental variations in temperature, water and atmospheric carbon dioxide (CO₂) concentration caused by regional climate change should affect the photosynthetic physiology of plants. Our objective was to investigate the response of S. purpurea to environmental variation.
Methods We irrigated natural alpine grassland to imitate rainfall increasing soil moisture and then used a portable gas exchange system (LI-6400) to measure photosynthesis parameters at the irrigated field (H) and a natural field (CK). During measurement, we set three levels of leaf temperature (15, 20 and 25 °C) and gradually elevated CO₂ concentration from 50 to 1 500 μmol·mol^-1.
Important findings CO₂, temperature and soil moisture affected photosynthesis parameters of S. purpurea significantly, and interactions were apparent among these three factors. Rising CO₂ gradually increased net photosynthetic rate (P_n) until it decreased at extremely high CO₂. Higher temperature caused P_n to decrease, but sufficient water supply partially alleviated the negative effect. Sufficient water supply increased P_n. With rising CO₂, intercellular CO₂ concentration (C_i) increased, transpiration rate (T_r) decreased, water use efficiency (WUE) increased and stomatal conductance (G_s) decreased; higher temperature caused G_s to decrease faster. The photosynthesis parameters above were also impacted by the combined actions of humidity and temperature. G_s was maximized at 20 °C, and sufficient water supply increased G_s further. C_i increased with increased temperature, and this response was more pronounced with sufficient water. T_r was positively correlated with temperature and soil water. Vapor pressure deficit (VPD) was directly proportional to temperature and decreased with sufficient water. Increased temperature and increased water supply made WUE decline. Therefore, increased soil water had compensatory effects on the relationship between high temperature and photosynthetic parameters.

Key words: CO₂ concentration, photosynthesis, soil moisture, Stipa purpurea, temperature

GUO Ya-Qi, BORJIGIDAI Almaz, GAO Qing-Zhu, DUAN Min-Jie, GANZHU Zhabu, WAN Yun-Fan, LI Yu-E, GUO Hong-Bao. Photosynthetic characteristics of Stipa purpurea under irrigation in northern Tibet and its short-term response to temperature and CO₂ concentration[J]. Chin J Plant Ecol, 2011, 35(3): 311-321.

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URL: https://www.plant-ecology.com/EN/10.3724/SP.J.1258.2011.00311

https://www.plant-ecology.com/EN/Y2011/V35/I3/311

Figures/Tables 8

Fig. 1 Daily variations of soil moisture during growing season from June to September.

Fig. 2 Response of net photosynthetic rate (Pn) of Stipa purpurea leaves to CO2 concentration under different soil moisture and temperature treatments (mean ± SD).

Fig. 3 Comparsion of net photosynthetic rate (Pn) (I), stomatal conductance (Gs) (II), transpiration rate (Tr) (III), vapour pressure deficit (VPD) (IV) of Stipa purpurea leaves at 370 and 570 μmol·mol-1 CO2 concentration under different soil moisture and temperatures (mean ± SD). Statistical analysis bars carrying same letter under the same temperature, having the same but case sensitive letter means significantly different at p < 0.05.

Fig. 4 Response of stomatal conductance (Gs) of Stipa purpurea leaves to CO2 concentration under different soil moisture and temperature treatments (mean ± SD).

Fig. 5 Response of transpiration rates (Tr) of Stipa purpurea leaves to CO2 concentration under different soil moisture and temperature treatments (mean ± SD).

Fig. 6 Response of vapour pressure deficit (VPD) of Stipa purpurea leaves to CO2 concentration under different soil moisture and temperature treatments (mean ± SD). CK, control treatment; H, irrigation treatment.

Fig. 7 Response of intercellular CO2 concentration (Ci) of Stipa purpurea leaves to ambient CO2 concentration under different soil moisture and temperature treatments (mean ± SD).

Fig. 8 Response of water use efficiency (WUE) of Stipa purpurea leaves to CO2 concentration under different soil moisture and temperature treatments (mean ± SD).

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Photosynthetic characteristics of Stipa purpurea under irrigation in northern Tibet and its short-term response to temperature and CO₂ concentration

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