毛白杨杂种无性系叶片δ^(13)C差异与气体交换参数

Difference in δ^(13)C and gas exchange parameters among Populus tomentosa clones

在苗木生长的不同时期对13个毛白杨(Populus tomentosa)杂种无性系叶片碳同位素δ13C和气体交换参数(净光合速率Pn、蒸腾速率Tr、瞬时水分利用效率WUEi、气孔导度Gs和胞间CO2浓度Ci)的差异进行研究,分析不同无性系间δ13C与气体交换参数的相互关系,目的在于探求δ13C在筛选高光合及高水分利用效率毛白杨杂种无性系中的应用价值。结果表明:不同生长时期和不同无性系间δ13C、Tr、WUEi、Gs和Ci的差异均显著,δ13C和WUEi表现为9月>7月,Tr、Gs和Ci表现为7月>9月,Pn在不同生长时期差异不显著。季节变化是引起毛白杨杂种无性系叶片δ13C差异的主要原因。同一时期,无性系间δ13C和WUEi表现出较好的一致性,即WUEi较高的无性系30、42、46、83、BL2和BL5,其δ13C值也较高,WUEi较低的无性系B331和TG34,其δ13C值也较低,且不同时期(7月和9月)δ13C和WUEi呈较强的正相关,相关系数r分别为0.7390和0.5458,高δ13C可以作为筛选高WUEi毛白杨的有效指标,且在苗木生长旺盛时期选育能得到更为可靠的结果。对毛白杨而言,高WUEi的无性系,一般具有适中或较低的Gs和Ci,但不一定具有很高的Pn,气孔调节使得毛白杨在不影响光合作用的同时保持较高的WUE。

Aims Fast, efficient breeding of fast-growth and high water use efficiency （WUE） in Populus tomentosa clones is a pressing need for afforestation in arid and semi-arid regions. There is much research on the correlation between stable carbon isotope and WUE in crops and a few trees, but little in different clones of P. tomentosa. Our objective was to explore the application of δ^13C on selection of clones with high photosynthesis and WUE. Methods We examined 13 clones of Populus-grafted seedlings in Beijing Forestry University （39°46＇ N, 116°19＇ E） Nursery in Beijing, China. We studied leaf δ^13C of the seedlings by MAT-251-MS in two different growth periods （mid-July and September） and gas exchange parameters （net photosynthetic rate （Pn）, transpiration rate （Tr）, instantaneous water use efficiency （WUEi）, stomatal conductance （Gs） and intercellular CO2 concentration （Ci）） by LI-6400 portable photosynthesis system between 9：30 and 11：30 a.m. in the same periods. Important findings Leaf δ^13C, Tr, WUEi, Gs and Ci significantly differed between the periods and among clones. Leaf δ^13C and WUEi were higher in July than September; however, Tr, Gs and Ci were lower in July than September and P, showed no significant difference between periods. The main reason for the difference of leaf δ^13C was seasonal variation. Leaf δ^13C and WUEi of the clones were consistent during the same period, i.e, the higher WUEi appeared in clones of 30, 42, 46, 83, BL2 and BL5 with higher δ^13C and the lower WUEi occurred in clones of B331 and TG34 with lower δ^13C. There was strong positive correlation between δ^13C and WUEi （r = 0.739 0 and 0.545 8 in July and September, respectively）; therefore, high δ^13C can be used as an effective indicator of high WUEi in Populus. Clones with higher WUEi may have moderate or low G, and C, but not necessarily high Pn.