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Taking the DH population of wheat cultivar Hanxuan10/Lumai14 as test object, and by the methods of correlation analysis and path analysis, this paper studied the relationships of the flag leaf stomatal density (SD), stomatal length and width (SL and SW), stomatal conductance (g(s)), photosynthetic rate (P(n)), and transpiration rate (T(r)) on the 10th and 20th day after anthesis with the yield and the index of drought-resistance under the conditions of drought stress and normal irrigation. Under the two conditions, most of the test leaf traits on the 10th day after anthesis had less correlation with the yield and the index of drought-resistance, whereas the leaf traits on the 20th day after anthesis had significant positive correlations with thousand kernel weight but less correlation with grain number per ear, grain yield per plant, and index of drought-resistance. Path analysis showed that g(s), P(n), and T(r) were the main factors affecting the grain yield per plant (YPP) and the index of drought resistance (IDR), and the effects were stronger both in direct and in indirect ways. The direct and indirect effects of SD, SL, and SW on the YPP and IDR were lesser. Under both drought stress and normal irrigation, and on the 10th and 20th day after anthesis, there were significant correlations between SD and SL, and between SL and SW, g(s), P(n), and Tr, but the correlations of SD and SL with g(s), P(n), and T(r) changed with water condition or growth stage. Therefore, it would be not always a good means to select the leaf stomatal density and size as the targets for breeding to improve the leaf stomatal conductance, photosynthetic rate, and transpiration rate, and further, to promote the yield.

Taking one hundred and fifty doubled haploid (DH) lines of winter wheat cultivars Hanxuan 10 x Lumai 14 as well as their parents as test materials, the genetic bases of top three leaves length, breadth, and angle at mid-filling stage, and their correlations with yield traits were studied under two water regimes rainfed (drought stress, DS) and well-irrigation (WI) in 2005-2007. Under DS, the leaf length and width of DH lines and their parents were significantly lower than those under WI, whereas the leaf angle had a miscellaneous variation. Under the two water regimes, all the test traits of DH lines had a transgressive segregation, with the variation coefficients ranged from 5.1% to 45.9%. The heritability and gene numbers for the given traits showed great differences. Under WI and DS, the heritability of flag leaf angle (FLA) was the highest (91% and 97%, respectively), and that of the third leaf angle (TLA) was the lowest (23% and 31%, respectively). However, the gene number for FLA (4 and 2 under WI and DS, respectively) was the least, and that of TLA (21 and 25, respectively) in 2007 was the most. Interactive effects were observed among the genes controlling FLA, second leaf angle (SLA), and TLA under WI and DS, and controlling third leaf length (TLL) under WI. The grain number per spike and the grain weight per spike were positively correlated with the length and width of top three leaves, and the thousand-grain weight and the yield per plant were significantly correlated with TLL, FLA, and SLA, but all correlation coefficients were smaller (0.481). It was suggested that the selection of top three leaves length and width should be carried out in the early generations of breeding procedure, while that of leaf angles should be carried out in advanced generations. An appropriate soil moisture regime retained in the critical growth period of the leaves would promote their growth and contribute to the grain yield.