Abstract:

Cinnamomum camphora is one of the dominant green species in the southern districts in China,and also acid rain is widespread contaminants in the environment.In this paper,we tried to study if photosynthetic characteristics of C.camphora seedlings planted in pots would change by irrigating with three different pH values(3.0,4.0,5.0)of simulated acid rain.The results showed that the light compensation point and saturation point of C.camphora fell under pH3.0,but rose under pH4.0 and pH5.0.Apparent quantum yield(AQY)increased by 54.53%,30.74%,and the net photosynthetic rate(P_n)increased by 27.07%,22.61% under pH3.0 and pH4.0,respectively,but decreased by 23.79% and 4.14% under pH5.0.The dark respiration rates(R_d)rose under three different pH treatments.The diurnal variation of P_n in C.camphora treated with acid rain presented the asymmetry double peak curves,occurring at 10:00 and 14:00 respectively.Midday depression of P_n was found at 12:00.The range of diurnal variation of P_n decreased by 27.68%,10.77%,28.90% under pH3.0,4.0 and 5.0 treatments,respectively,but under pH3.0 and 4.0 treatments,the daily P_n all ascended.The minimum of stomatal conductance(G_s)decreased by 19.38%,70.93% and 14.10% in view of different pH values(3.0、4.0、5.0)of simulated acid rain,but the maximum increased by 40.12%,24.39% and the range of diurnal variation of G_s increased by 61.29%,58.31% under pH3.0 and 4.0,respectively.The minimum of intercellular CO₂ concentration(C_I)increased by 13.22%,9.87%,3.27%,but the range of diurnal variation of stomatal limit(L_s)decreased by 33.15%,43.31%,52.35% under pH3.0,4.0,5.0 treatments,respectively.

Key words: simulated acid rain, Cinnamomum camphora, seedling, photosynthetic characteristics