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: This study was conducted to investigate the effect of atmosphere-leaf vapor pressure deficit (VPD) in Allium microdictyon Prokh. and Allium ochotense Prokh. The vapor pressure deficit (VPD) was rapidly increased with increasing temperature and decreasing relative humidity. Taken as a whole, the stomatal transpiration reaction was slightly late with increading of VPD. Maximum photosynthetic rate at high-VPD condition was 5.98 µmol CO 2 · m −2 · s −1 in Allium microdictyon, which was a little lower than 6.59 µmol CO 2 · m −2 · s −1 in Allium ochotense, respectively. After 2 p.m, stomatal transpiration of Allium microdictyon at the high VPD condition were rapidly decreased. Ci/Ca began to decline sharply at 8 a.m and showed the lowest value at 2 p.m, The results showed that Ci/Ca decreased with being used CO 2 in the mesophyll intercellular space for photosynthesis. In high VPD condition, The water potential values showed the highest at 5 a.m, and the lowest at 1 p.m in high VPD condition. The water saturation deficits (WSD) in high VPD condition showed about 1.5 times higher than in low VPD condition. The results indicated that physiological activities in Allium microdictyon is more limited from high VPD conditions.

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: This study was conducted to investigate the changes of chlorophyll contents, chlorophyll fluorescence, photosynthetic parameters, and leaf growth of Synurus deltoides under different shading treatments. S. deltoides was grown under non-treated (full sunlight) and three different shading conditions (Shaded 88~93%, 65~75%, and 45%~55%). Light compensation point (L comp ), dark respiration (D resp ), maximum photosynthesis rate (Pn max ), photo respiration rate (P resp ), carboxylation efficiency (Φ carb ), and photochemical efficiency were decreased with increasing shading level; However, CO 2 compensation point (CO 2 comp ), total chlorophyll content, and specific leaf area (SLA) were shown the opposite trend. S. deltoides under 88~93% treatment showed the lowest photosynthetic activity such as maximum photosynthetic rate (Pn max ), photochemical efficiency, and CO 2 compensation point (CO 2 comp ). Therefore, photosynthetic activity will be sharply decreased with a long period of 8~12% of full sunlight. With the shading level decreased, carotenoid content and non-photochemical fluorescence quenching (NPQ) increased to prevent excessive light damage. This result suggested that growth and physiology of S. deltoides adapted to high light intensity through regulating its internal mechanism.