Comparison of photosynthetic characteristics between two herbaceous peony (Paeoniaceae) cultivars.
The photosynthetic characteristics of two herbaceous poeny(Paeonia lactiflora Pall.,Paeoniaceae) cultivars were studied by the portable photosynthesis system(LI-6400).The results showed that diurnal changes of net photosynthetic rates(Pn) in leaves of the two cultivars presented a typical bimodal curve;both had 'Midday depression' phenomenon,and the highest Pn for 'Zhusha Pan' and 'Huang Jinlun' was 16.33 ?mol·m-2·s-1,18.25?mol·m-2·s-1,respectively at 8:00 A.M.There was significant difference in stomatal conductance(Cond),intercellular CO2 concentration(Ci),transpiration rate(Tr) as well as water usage efficiency(WUE) between two cultivars.The relationship between Pn and other factors for photosynthesis with each cultivar was studied,and the equations were Pn=-3.9989-0.0008PAR-1.5078Ta+1.4596Tleaf-0.1038RH+84.767Gs+0.0443Ci-0.2625Tr(R2=0.975) and Pn=-18.3765+0.0086PAR+0.2402Ta+0.3663Tleaf+0.4994RH+34.7959Gs-0.076Ci-2.0367Tr(R2=0.991),respectively.The reason for the depression of Pn for two cultivars was different,for 'Zhusha Pan',the reason is non-stomatal factor,and for 'Huang Jinlun',however,it is stomatal factors.