Abstract:
It is difficult to identify the gender of dioecious seedlings, and the population characteristics are easily affected by the gender differences of seedling stress resistance. The male and female cuttings of
Broussonetia papyrifera were treated for 60 days at mild, moderate and severe drought respectively, and leaf characteristics, photosynthetic pigments and photosynthetic parameters were measured to analyze the gender differences of the effects of drought intensity on photosynthesis of seedlings. The results showed that: (1) There was a significant gender differences in drought stress on the photosynthetic leaf area of the seedlings (
P<0.05). The female plants responded to drought by reducing leaves number and the male plants by reducing single leaf area and increasing leaf thickness, but total photosynthetic leaf area of female plants was significantly lower than that of male plants (
P<0.05). (2) Drought stress significantly affected the composition and content of photosynthetic pigment in seedlings (
P<0.05), and the order was Caro > Chla+b > Chla > Chlb > Chla/b. Chla and Chla+b content of female plants were significantly higher than those of male plants (
P<0.05), but there were no gender differences in Chlb, Caro content and Chla+b (
P>0.05); (3) Drought stress significantly affected photosynthetic parameters of seedlings (
P<0.05), and mild drought was beneficial for Pn and Gs, moderate drought was beneficial for Tr and
Ci, severe drought inhibited photosynthesis. Gender had significant influence on photosynthetic parameters (
P<0.05), the order of the influence was
Tr >
Pn >
Ci >
Gs. The actual Pn of male plants was higher than female plants, while the potential Pn was lower than that of female plants. In conclusion, male and female seedlings adopt different strategies of adjusting photosynthetic leaf area, pigment and photosynthetic rate to cope with drought and the photosynthetic capacity of male plants was stronger than that of female plants.