Diurnal Variation of Photosynthetic Characteristics In Coolidge Pineapple Guava

The pineapple guava (Feijoa sellowiana Berg.), a great commercial plant for its fruit quality and unique flavor, has been introduced into China in recent years. To better grow this plant for orchard, the diurnal variations of photosynthesis on Feijoa sellowiana ‘Coolidge’ were studied using a Li-6400 portable photosynthesis system. Relationships between net photosynthetic rate (Pn) and its physio-ecological factors, including photosynthetic active radiation (PAR), relative humidity of the air (RH), temperature of leaves (Tl), atmospheric CO₂ concentration (Ca), stomatal conductance (Cond), intercellar CO₂ concentration (Ci), and transpiration rate (Tr) etc. were determined by path analysis and stepwise regression equation. The curve of diurnal variation of Pn was demonstrated two peaks in a clear day, which appeared at 12:00 and 14:00, respectively. There was a clear depression at noon. Correlation analysis showed that there were positive relationship between Pn with Cond and Tr. Their correlation equations were Pn=6.1883 Cond2+66.0030 Cond-0.6763, (R2=0.893) and Pn=0.5473 Tr3-5.9285 Tr2+22.1925 Tr-18.042, (R2=0.914), respectively. Among the ecological factors, PAR was the major one that influenced the variations of Pn. Cond and Tr were two key physiological factors that influenced the variations of Pn. The correlation equation between Pn and the major physio-ecological factors was Pn=73.82-0.0041 PAR+1.8069 RH+1.9585 Tl-0.4479 Ca-102.62 Cond+3.6657 Tr-0.1354 Ci (R2=0.999). This study can provide foundational data on the physiological ecology in pineapple guava for its introduction, cultivation and production.