Abstract:

Bermudagrass (Cynodon dactylon L.), as wildly used turfgrass, is often subjected to extreme drought stress resulting in dehydration of leaves. In this paper, the effects of dehydration stress on the photochemical activities of photosystems including photosynthetic system 2 (PSⅡ) and photosystem 1 (PSI) of bermudagrass leaf were studied using fast chlorophyll fluorescence transient and 820 nm light absorption technology. The results showed that dehydration in the dark degraded the leaf chlorophyll and severely damaged the photochemical activity of the photosynthetic apparatus. With the exacerbation of dehydration, the activity of PSI and PSⅡ decreased gradually and significantly. The decrease of PSI activity (ΔI/Io) was earlier and more serious than the decrease of PSⅡ (Fv/F and Ψo). It demonstrated that the PSI activity was more sensitive to dehydration than PSⅡ activity. The photosynthetic performance index based on light energy absorption basis (PI_ABS) accurately and sensitively reflected the response of photosynthetic electron transport chain leaf between two photosystems of Cynodon dactylon L. to dehydration in the dark, and could be used as a rapid and effective index for cultivation and identification of drought tolerance varieties of bermudagrass.

Key words: Cynodon dactylon L., Dehydration, Photosynthesis apparatus, Chlorophyll a fluorescence transient

摘要：

狗牙根（Cynodon dactylon L.）作为应用广泛的草坪草时常会遭遇极度干旱胁迫从而造成叶片脱水。本文采用快速叶绿素荧光以及820 nm光吸收技术，研究了脱水胁迫对狗牙根叶片光合机构包括光系统2（PSⅡ）和光系统1（PSⅠ）光化学活性的影响。研究结果表明脱水导致狗牙根叶片叶绿素降解，严重伤害狗牙根叶片光合活性。随着脱水程度的加重，PSI和PSⅡ活性的受损程度增加，其中，PSⅠ活性（ΔI/Io）的下降在时间上先于PSⅡ活性（Fv/Fm和Ψo）的下降，且PSⅠ活性下降程度大于PSⅡ活性下降程度。这说明PSⅠ活性较PSⅡ活性对脱水更敏感。以光能吸收为基础的光合性能指数（PI_ABS）准确灵敏地反映了狗牙根叶片光合电子传递链对脱水的响应，可作为狗牙根耐旱品种培育及鉴定的一种快速有效的检测指标。

关键词: 狗牙根, 脱水, 光合机构, 快速叶绿素荧光