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Scientia Silvae Sinicae ›› 2015, Vol. 51 ›› Issue (1): 29-41.doi: 10.11707/j.1001-7488.20150104

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Short-Term Responses of Leaf Gas Exchange Characteristics to Drought Stress of Cotinus coggygria Seedlings

Li Jinhang, Qi Xiuhui, Xu Chengyang, Wang Chang, Liu Haixuan, Sun Peng   

  1. Key Laboratory for Forest Silviculture and Conservation of Ministry of Education, Key Laboratory for Silviculture and Forest Ecosystem in Arid and Semi-arid Areas of State Forestry Administration, Beijing Forestry University Beijing 100083
  • Received:2014-04-15 Revised:2014-07-20 Online:2015-01-25 Published:2015-01-23

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Abstract:

[Objective]This research was carried out to investigate the short-term responses and regular patterns of leaf gas exchange characteristics of Cotinus coggygria seedlings, collected from different locations, to soil water stress.[Method]A field experiment was set and the one-year-old C. coggygria seedlings were collected from three locations: Xishan Mountains in Beijing, Taishan Mountains in Shandong Province and Jiangxian County in Shanxi Province. The seedlings were subjected to three water regimes, including control (CK, 75%-80% of field water capacity), moderate stress (MS, 55%-65% of field water capacity) and severe stress (SS, 35%-45% of field water capacity). A LI-6400 portable photosynthesis measurement system was used to determine the light response curves (Pn-PAR) and CO2 response curves (Pn-Ci) of the mature leaves, and the statistical analysis software SPSS 20.0 was applied to fit the curves. Each photosynthetic parameter was calculated according to Levenberg-Marquardt iterative principle of nonlinear least square method.[Result]1) The CO2 assimilation ability of C. coggygria seedlings decreased significantly (P < 0.05) as drought stress degree increased and drought stress time prolonged. The decrease was mainly ascribed to block of CO2 diffusion and photosynthetic electron transport and decline of light energy utilization efficiency when water deficit occurred. The stomatal conductance to CO2 + mesophyll diffusion conductance to CO2(gsc+ gm), apparent quantum yield (AQY), light saturation point-light compensation point (LSP-LCP), maximum electron transport rate (Jmax) and maximum electron transport rate / maximum carboxylation rate (Jmax / Vc,max) of C. coggygria seedlings treated with severe stress were lower than those in control by 50.5%, 12.0%, 21.0%, 37.9% and 16.9%, respectively. The gsc, gm, AQY, LSP-LCfP and Jmax / Vc,max of C. coggygria seedlings during late stage of drought stress were lower than those during mid-stage of drought stress by 18.7%, 81.0%, 19.3%, 4.6% and 5.5%, respectively. 2) Water deficit promoted the low light use efficiency and carboxylation rate of C. coggygria seedlings to a certain extent. 3) The limitation on photosynthesis due to stomatal conductance to CO2 (ls) and due to mesophyll diffusion conductance (lm) treated with moderate and severe drought stress were higher than that in control by 36.9% and 25.3%, 9.7% and 103.0%, respectively. Thus, stomatal limitation and mesophyll diffusion limitation were the main reasons for net photosynthetic rate decline under moderate drought stress and severe drought stress environment, respectively. Additionally, the average drought-treated ls and lm treated were higher than those in control by 17.7% and 46.0%, and those during late stage of drought stress were higher than those during mid-stage of drought stress by 47.0% and 71.1%, respectively. 4) Compared with those seedlings before drought stress treatment, the light-saturated maximum net photosynthetic rate (Pn,max), CO2-saturated maximum photosynthetic capacity (Amax), maximum net photosynthetic rate limited by Rubisco activity and amount (Ac,max), maximum net photosynthetic rate limited by RuBP regeneration (Aj,max), Vc,max, triose phosphates utilization rate (VTPU) of seedlings under SS treatment were all declined, and those declines of seedlings from Shanxi were greater than those of seedlings from Beijing and Shandong by 38.0% and 50.3%, 40.7% and 46.3%, 45.7% and 51.2%, 52.4% and 54.2%, 47.3% and 55.8%, 55.5% and 82.6%, respectively. However, the LCP and dark respiration rate (Rd) of seedlings from Shanxi Province under continuous drought stress were lower than seedlings from Beijing and Shandong Province by 31.2% and 47.5%, 27.2% and 9.2%, respectively. [Conclusion]There were significant differences in the sensitivity to continuous drought stress among the C. coggygria seedlings from the three locations of Xishan Mountains in Beijing, Taishan Mountains in Shandong Province and Jiangxian County in Shanxi Province. The leaf carbon assimilation ability of seedlings from Shandong under severe drought stress was remarkably stronger than that from Beijing and Shanxi, and the ability of seedlings from Beijing was significantly stronger than seedlings from Shanxi. The diffusive resistance to CO2 and photosynthetic electron transport resistance of seedlings from Shanxi were significantly greater than seedlings from the other two locations, while the LCP and Rd were the smaller than the other two locations. Consequently, the photosynthetic characteristic parameters of C. coggygria seedlings from Jiangxian County in Shanxi changed more violently than those from Xishan Mountains in Beijing and Taishan Mountains in Shandong in response to arid environment, however, the seedlings from Shanxi were more capable of lowering the light compensation point and the level of dark respiration metabolism to ensure accumulation of photosynthetic assimilation products than those from the other two locations.

Key words: Cotinus coggygria seedlings, drought stress, leaf gas exchange, mesophyll diffusion limitation, stomatal limitation

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