Photosynthesis in Relation to Growth and Distribution of Fruit in Peach Trees

Abstract

The rate of photosynthesis and the total daily photosynthesis of a peach tree [Prunus persica (L.) Batsch.] were found to be closely related to changes in carbon requirements caused by changes in the stage of fruit growth and by fruit removal at harvest. Although the light regime was superior in the topmost zone of leaves, the rate of photosynthesis was lower than in intermediate zones during the period of most rapid fruit growth. In contrast, the rate of photosynthesis in the horizontal zones of the tree was closely related to the weight of fruit per unit of leaf area in each zone. This coupling between supply and demand was also demonstrated by assimilate build up in the leaf when fruit were removed, i.e. 14C turnover was substantially reduced. During the final stage of rapid fruit growth (DW III) the growth of fruit was stimulated above and inhibited below a cincture through the phloem of the main branches, which indicated that the level of assimilate available for fruit growth was lower in the bottom of the tree. This conclusion was supported by the observation that the mean leaf density (mg dry weight/cm�) increased with increasing height in the canopy. It was concluded that the data were good evidence of a strong coupling between the supply of assimilates by the leaves and the growth requirements of the tree.

Fruiting Effects on Leaf Characteristics, Photosynthesis, and Root Growth in Peach Trees.

“…The percentages of the chloroplast compartment area per cross-section of a chloroplast from leaves of defruited trees were 48.8% in spongy cell and 50.5% in palisade cell, whereas the percentages were 91.4% and 83.5%, respectively, in leaves of fruiting trees. The Pn of leaves from fruiting and non-bearing trees are similar to that reported by Hansen (1970), Chalmers et al (1975), Fujii and Kennedy (1985), De Jong (1986), and Wood (1988. However, other researchers using other plant species have questioned the effects of carbohydrate accumulation in leaves on the photosynthetic rate (Ballantine and Forde, 1970;Wilkinson and Beard, 1975;Geiger, 1976;Hariri and Brangeon, 1977;Carmi and Shomer, 1979;Melis and Harrey, 1981;Lichtenthaler et al, 1982).…”

“…That photosynthetic rates differed between leaves of fruit trees with and without fruits is well known; fruiting actively promotes the photosynthesis of an individual leaf during the fruit maturation period (Chalmers et al, 1975;Fujii and Kennedy, 1985;De Jong, 1986;Wood, 1988). The reduction in Pn as a consequence of decreasing sink strength through fruit thinning is attributed to increased carbohydrate levels in leaves, a form of feed-back inhibition (Noel, 1970;Milford and Pearman, 1972;Thorne and Koller, 1974;Nafziger and Koller, 1976).…”

Tansley Review No. 27 The control of carbon partitioning in plants

“…These two examples refer to reproductive growth and probably the strongest case for sink limited photosynthesis is provided by the relation between high photosynthetic rates and fruiting. This has been shown for example with apples (Maggs, 1963), pea (Flinn, 1974), peach (Chalmers et al, 1975), pepper (Hall & Milthorpe, 1978) and soybean (Kokubun & Watanabe, 1983;Seddigh & Jolliff, 1984). A similar response is also associated with other rapidly growing storage organs such as potatoes (Burt, 1964;Nosberger & Humphries, 1965) and tuberous roots (Hozyo & Park, 1971).…”

Carbon allocation in fruit trees: from theory to modelling

“…3). Similarly, a decrease in photosynthesis with low fruit loads has been observed for different tree species (Gucci et al 1995;Chalmers et al 1975;BenMimoun et al 1996;Franck et al 2006;Iglesias et al 2002;Syvertsen et al 2003). The diurnal variation of leaf carbohydrate content (Fig.…”