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Perspectives on physiology in support of fruit production and future opportunities: lessons from 40 years of fruit research

Lakso, A. N.
Acta horticulturae 2017 no.1177 pp. 1-12
apples, carbon, field experimentation, fruiting, genetics, humid zones, irrigation scheduling, molecular biology, monitoring, remote sensing, researchers, simulation models, soil, stomatal movement, temperature, trees, vines, woody plants
For many years fruit crop physiology was primarily explanatory of processes and behaviors that growers already understood how to manipulate. Our research in the past 40 years has focused on the physiological bases directly related to practical issues for growers and attempted to provide opportunities for physiology to improve practice. Several examples of this approach are reviewed. (1) Fundamental studies of apple tree carbon relations combined with simulation modeling of supply/demand balances and the interacting effects of light and temperature identified the period of greatest carbon deficit for fruit development to be 1-3 weeks after bloom. Although originally a research tool, the simulations of yearly weather in combination with long-term field trials by collaborators led to the utilization of the model to estimate weather-induced tree sensitivity to chemical thinners. The simulations provide growers with real-time estimates of carbon balance via the web leading to improved regulation of cropping via chemical thinning. (2) Studies of apple tree water relations, and specifically regulation of stomatal behavior and aerodynamic coupling to the environment, identified an unusual stomatal response to VPD. It was found that apple ET in a cool humid climate was not well predicted by ETo. This has led to the development of an apple-specific Penman-Monteith ET model that is available on the web for growers to refine irrigation scheduling. (3) The lack of practical automated methods of monitoring dynamic tree or vine water potentials stimulated the development of an electronic microtensiometer for continuous monitoring of soil and plant water potentials. The sensor has calibrated over a wide range of water potentials and will provide possibilities to embed inside woody plants to monitor stem water potentials. All of these advances required close collaboration with researchers of varying disciplines, extension specialists and growers. In the future, this type of fruit physiology research will be needed to provide whole-plant physiological understanding in relation to remote sensing, molecular biology and genetics.