PHOTOSYNTHETIC CHARACTERISTICS OF AVOCADO LEAVES

An understanding of the impact of environmental conditions and cultural practices on avocado leaf photosynthetic performance will not only address the lack of knowledge in this area, but also help growers make decisions about the timing of cultural practices to optimize photosynthetic performance and, in turn, yield. Our work to date has resulted in a better understanding of the basic photosynthetic performance of avocado leaves. New leaves of the spring flush attain a net positive photosynthetic rate approximately 17 days after emergence and reach their maximum photosynthetic capacity 40 to 50 days after emergence. The leaves that developed during the previous season are the primary photosynthetic sources until new leaves begin to contribute to the net carbon gain of the plant, at which point the photosynthetic capacity of older leaves declines. We have found that the hot, dry summer climate of southern California results in high temperature and low humidity stress on avocado leaves, resulting in optimal leaf photosynthesis for a relatively short portion of the day. There is evidence, however, that certain cultivars of avocado may not be affected as severely by these stresses as others. We are currently investigating the use of cultural practices to prolong this period of optimal photosynthesis.