A Study of Total Photosynthesis Rate and Growth Pattern in Nine Asian Pear (Pyrus serotina Rhed) Cultivars Grown under Tehran Environmental Conditions

Knowledge of environmental and ecological factors as well as growth and development pattern of fruit trees is an important task in orchard management and fruit industry. In addition, determination of growth pattern is an important aspect in the orchard management system. In this research, the total photosynthesis rate and growth pattern was measured in nine Asian pear cultivars. Experiment was arranged as split plot design in time based on randomized complete block design (RCBD) with 9 cultivars and 14 sampling time, in 5 replicates. According to results, significant differences (P≤0.01) were observed in the amount of total photosynthetic rate, among cultivars and sampling times. Among the studied cultivars, ‘KS13’ with 17.10 and ‘KS14’with 11.15 μmol CO2 m-2 s-1, had maximum and minimum of total photosynthesis rate, during 14 weeks measurement, respectively. The highest total photosynthesis rate (25.24 μmol CO2 m-2 s-1) was observed in the week 14th, whereas the lowest amount (7.37 μmol CO2 m-2 s-1) was obtained in the second week of measurements. According to the results, ‘KS13’ and ‘KS6’ cultivars showed highest total photosynthetic rate. Also, seasonal changes in cumulative vegetative (branches) and reproductive (fruit) growth were measured during the growing season. Results indicated the existence of a simple fruit sigmoid growth curve for all studied cultivars. However, duration of each cumulative fruit growth phase was different among the studied cultivars. The growth reduction phase was happened 62 days after full bloom (DAFB) in KS13, KS14 and KS12 cultivars and 72 DAFB in the KS6, KS7, KS8, KS9, KS10 and KS11 cultivars. Results indicated that KS7, KS10, KS11 and KS14 are early; KS6, KS9, KS13 are mid-season, and KS8 and KS12 are late-season maturing fruit cultivars. Fruit data revealed that these cultivars have good adaptation to Tehran environmental conditions with optimum crop yield as a result of optimum photosynthesis activity during the growing season. In conclusion, the obtained results on vegetative and reproductive growth can be used for better and improved management of Asian pear orchards grown under Tehran environmental conditions.