Study on Diurnal Variation of Photosynthesis for OAioglossum thermale Kom and Its Relation to Environmental Factors

The diurnal variation of photosynthesis for OAioglossum thermale Kom leaves had been studied under the natural conditions.The results were as follow: In autumn clear days,the curves of diurnal variations of net photosynthetic rate(Pn) had two peaks,which had an obvious phenomenon of midday decline of photsynthetic efficiency.The mid-depress of Pn was principally caused by non-stomatal limited elements i.e,photo in hibition and photo respiration.The optimal equation of the diurnal variation of Pn was attained by the method of stepwise multi-regression.The analys is of partial correlation and path coefficient on Pn and factors showed that the diurnal variation of Pn had closer relation to photosynthetic active relation(Q),air relative hum idity(RH),and CO2 concentration(Ca) in the air.Q,RH and Ca were the primary direct factors affecting Pn.