Ecophysiological responses of leaves and fine roots of Indocalamus barbatus Mcclure seedlings to heat and drought

摘要

This study investigated the impact of global warming and the resulting hot and arid climate on the growth and afforestation of I ndocalamus barbatus McClure seedlings. Different naturally occurring conditions of heat and drought were simulated in order to observe the ecophysiological responses to them in 2a I . barbatus seedlings, such as leaf gas exchange, fine root and leaf water potential, and antioxidase activity. The results showed that the following. 1) 2a I . barbatus seedlings responded differently to different heat and drought conditions; elevated temperatures significantly increased the transpiration rate and stomatal conductance, but non-stomatal limitations caused a decrease in the photosynthetic rate and restricted diurnal fluctuations in photosynthesis under extreme heat conditions. 2) Under moderate drought and its compounded conditions with heat, stomatal limitations caused a decreased photosynthetic rate. 3) Under severe drought and its compounded conditions with heat, the physiological processes of seedlings were severely impacted, and this was further compounded by the effects of high temperature, resulting in significantly decreased rates of transpiration, photosynthesis, stomatal conductance, and water use efficiency. 4) In the control, high temperature, and extreme temperature groups, water potential decreased more dramatically in fine roots than in mature leaves. 5) The effects of heat and drought on three types of antioxidases in the fine roots and mature leaves were consistent; superoxide dismutase activity in fine roots was higher than in mature leaves, while the reverse was observed for catalase and peroxidase activity. Therefore, fine roots are a critical structure in the adaptation of I . barbatus seedlings to heat and drought, as water absorption organs are more sensitive than transpiration organs. This study showed that I . barbatus seedlings are relatively resistant to heat and drought, and are able to increase the ecophysiological adaptability of the leaves and fine roots within certain temperature and humidity ranges. In particular, under compounded conditions, heat and drought have a synergistic effect on growth performance in plants. Extreme drought, however, results in damage to gas exchange mechanisms in leaves, as well as an impaired water intake in leaves and fine roots. Therefore, I . barbatus is not suitable for long-term cultivation under extreme drought condition, as high temperatures will aggravate the aforementioned damage.