Title: PHOTOSYNTHETIC RESPONSES OF CITRUS TO ENVIRONMENTAL CHANGES
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: November 24, 1998
Publication Date: N/A
Interpretive Summary: Citrus is one of the major fruit crops in world trade today. Yield of citrus, similar to other crops, is the net result of photosynthesis, a process by which leaves absorb carbon dioxide (CO2) from the air to make components required for growth and development. The rate of photosynthesis is dependent on a series of reactions, each of which potentially has a unique response to environmental stress. The ability of citrus to adapt and/or compensate for environmental stress is critical to its survival and performance. Current knowledge of citrus photosynthesis in response to changes in sunlight, air temperature, available soil water, and atmospheric CO2 is limited. This hinders the development of highly productive cultivars tolerant to environmental stress. An understanding of how citrus reacts to environmental stress and which pathways and/or products are affected is required before genetic engineering can be employed to produce stress-tolerant plants.
This review examines current understanding of the physiology and biochemistry of citrus photosynthesis in response to changes in solar irradiance, air temperature and humidity, soil water availability, and growth CO2. Unfavorable changes in the environment affect stomatal and nonstomatal components of the CO2 exchange rate (CER), modify characteristics of key photosynthetic enzymes, alter synthesis and partitioning of photosynthates, and reduce citrus productivity. Elevated CO2 enhances citrus CER, growth and yield, and can compensate for adverse effects of high temperature, high vapor pressure deficit, decreased available soil water and low light intensity on photosynthesis. Certain biochemical and metabolic features could contribute to citrus growth and survival under suboptimal conditions. There is indeed a critical need to explore more deeply how citrus responds to stress, to understand the mechanisms of stress responses, and to identify the targets for a genetic/breeding approach designed to enhance stress tolerance/resistance.