Objective: To study the diurnal variation of net photosynthetic rate (P(n)) and main influencing factors in different types of Pueraria thomsonii, aimed at providing the theoretical basis for breeding the fine varieties of P. thomsonii suitable for the local light condition.
Method: Diurnal variations of photosynthesis in leaves of different types of P. thomsonii were determined with the Li-6400 Portable Photosynthesis System.
Result: (1) Diurnal variation of P(n), transpiration Rate (T(r)), stomatal conductance (G(s)) in leaves of six varieties of P. thomsonii showed unimodal curve and asymmetric bimodal curve. Diurnal variation of water use efficiency (WUE), intercellular CO2 concentration (C(i)) showed single valley curve. Diurnal variation curve of stomatal limitation value (L(s)) was single peak and S-type. (2) P(n) in leaves of six varieties of P. thomsonii was positively correlated with photosynthetic active radiation (PAR), air temperature (T(a)), G(s), and negatively correlated with air relative humidity (RH), C(i), P(n) of all varieties were very significantly correlated with PAR, G(s).
Conclusion: Diurnal variations of photosynthesis in leaves of different types of P. thomsonii show significant difference. Jiuding, Chuanyu, Gange, Dijin No. 1 planted in Ya'an overcome "midday depression" phenomenon. Hechuan has the greatest photosynthetic potential, suitable for planting in forest understory and intercropping with high stalk to avoid the strong flashes. Planted in long-day region was beneficial to its growth. CO2 use efficiency of Geboshi No. 11 and Dijin No. 1 were significantly higher than that of the others. The accumulation efficiency of organics can be increased in cultivation management by fertilizing CO2.