Effects Of Simulated Warming On Growth And Water Utilization Of C₃and C₄Plants

In order to investigate the response of growth and water utilization of C3and C4plants to climate warming, author regarded Stipa bungeana(C4) and Bothriochloa ischaemum(C4) as objects, which are coexisting in Inner Mongolia typical warm temperate grassland. OTC (Open Top Chamber) was designed to simulate warming, and the seed emergence, seedling morphology, photosynthetic parameters, leaf water physiological characteristics, water consumption, biomass accumulation, biomass allocation and water use efficiency of the two plants were observed to reveal the growth characteristics, water consumption and water use policies of C3and C4plants in the treatment of warming. The results can provide the basis for further research of the composition, distribution and adaptability of C3and C4plants under climate warming. The main conclusions as follow:(1)Simulated warming(1.34℃) significantly increased the seed emergence percentage and emergence rate of two plants. However, compared with S.bungeana (C3), warming played a greater role in promoting the seed emergence percentage and emergence rate of B.ischaemum(C4), and also decreased its seedling mortality percentage and seedling mortality rate. Therefore, the B.ischaemum(C4) showed a larger emergence advantage.(2)The morphological growth of C3and C4plants responded to warming in different ways. Leaves of B.ischaemum(C4) grew exuberantly and leaf water retention capacity was strong in the early period (July). While the height of S.bungeana (C3) increased significantly in both early and later period (September).(3)The biomass accumulation of C3and C4plants responded to warming in different ways. The shoot biomass, root biomass and total biomass of B.ischaemum(C4) increased significantly in the early period as the promotion of warming to growth. However, due to the slowing growth rate, the biomass accumulation of B.ischaemum(C4) had no significant change in the later period. The biomass accumulation of S.bungeana (C3) had no significant change in early or later period. The simulated warming had no significant effect on root-shoot ratio of C3and C4plants.(4)The stomatal conductance(gs) and transpiration rate(Tr) of S.bungeana (C3) increased significantly in the treatment of warming, but the net photosynthetic rate(Pn) did not change significantly, therefore led to a slight decrease in water use efficiency of leaves. The gs, Tr and Pn of B.ischaemum(C4) increased significantly in the treatment of warming, but the increase of Pn was greater than Tr, and thus led to an increase in water use efficiency of leaves. The water use efficiency of B.ischaemum(C4) was higher than S.bungeana (C3).(5)In the later period, the water use efficiency of individual level was lower due to the large amount of water consumption of S.bungeana (C3). While the water use efficiency of individual level of B.ischaemum(C4) was higher compared with S.bungeana (C3) although its Tr and total water consumption increased greater than that of S.bungeana (C3). Therefore, B.ischaemum(C4) may be a high water consumption and high water use efficiency specie.In conclusion, compared with S.bungeana (C3), B.ischaemum(C4) showed greater growth and water utilization advantages in the treatment of warming through seed emergence, vigorous early growth and higher water use efficiency. Based on these results we can predict that the B. ischaemum(C4) will benefited from the air temperature rise of2℃in the future.