Corelli and Lakso- Effects of physiological factors and environmental conditions on fruit growth

L'effetto di fattori fisiologici e delle condizioni ambientali sullo sviluppo dei frutti

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Luca Corelli Grappadelli1* e Alan N. Lakso2
1 Dipartimento Colture Arboree, Università di Bologna, Viale Fanin 46, 40127 Bologna
2 Dept. Horticultural Sciences, N.Y.S.A.E.S. - Cornell University, Geneva, NY (USA)

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Effects of physiological factors and environmental conditions on fruit growth

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Key words: apple, cell division, carbon balance, light, apple, peach, temperature.

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Abstract

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This paper focuses on the processes occurring in the fruit between fertilization and harvest, with particular emphasis on some physiological, energetic and modelling aspects affecting the growth of this organ. As fruits transition from flower to actively growing fruitlets, cell division sets the bases for final fruit size, which is the result of the product cell number x cell volume. If cell volume is relatively constant, a fruit with more cells should be larger at harvest. The importance of the cell division phase has been confirmed in apples that show a correlation between fruit growth during this early stage and final fruit size. Fruit growth rates have in turn been correlated to daily temperature regimes: warmer temperatures can induce faster growth in the initial stages, and can thus result in larger fruit at harvest. Cell volumes may also vary in fruits adding variation to final size. The interplay of length of season and temperature regimes needs to be evaluated along with other factors that influence this process, such as the type of leaves that support fruit growth, the light microclimate, crop load, vegetative growth and changes in the fruit anatomy/physiology. Along with endogenous hormones, nutrients and water relations involved in the control of fruit growth, the plant carbon balance plays a major role. The energy required for fruit growth expressed by their cost of production is more or less constant per fruit during the growing season, despite the fact that, depending on the type of organ (i.e. stone vs. pome fruit), the specific cost of production of different tissue components (e.g. mesocarp vs. endocarp or seed proper) may vary widely. The cost of production of organs is useful as it provides a uniform expression for comparison to photosynthetic energy production. In conclusion, there are many factors capable of influencing the growth of the fruit, and also the quality attributes that the fruit attain after harvest. Knowledge and integration of these factors is important if the goal is to produce large amounts of top quality fruit.

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