Fruit Shape

Fruit weight or diameter is not the only important result of fruit growth. Fruit shape may change over the season of growth, giving unique forms to different fruit. The general shape of fruit is determined relatively early in fruit development (i.e., young fruit generally look very similar to mature fruit). Several fruit, however, have distinctive features. Examples are peaches, apricots, and other stone fruit that have a pronounced suture groove running the length of the fruit, and the 'Delicious' apple, with its distinct conical shape and five lobes.

Changes in fruit shape over the season are the result of differential growth of tissues in particular locations in the fruit, such as the lobes in the 'Delicious' apple (Figure F3.5). The difference in growth may be due to more or less growth in certain tissues, to a difference in the type of cells produced (e.g., smaller, more compact cells), or to the relative growth differences in one dimension versus another. For example, because the relative growth of apple flesh is somewhat greater in the radial direction than in the longitudinal direction, the shape of an apple tends to become more oblate (wider) as it grows. Many fruit develop under hormonal stimuli from seeds, so that a failure of seed development may alter fruit shape dramatically.

Temperate tree fruit exhibit several different patterns of fruit growth. Within a species, the pattern of fruit growth depends on the

MONTH BEFORE BLOOM (LATE APRIL]

AT HARVEST (EARLY OCTOBER|

FLOWER AT BLOOM

OVARY AND SEED CAVITY AT BLOOM

3 MONTHS (HID AUGUST I

FRUIT 2 MONTHS AFTER BLOOM (MID JULY)

FIGURE F3.5. Development of size and form of'Delicious' apple fruit from its inception in the flower to the fruit at harvest dimension monitored—diameter, fresh weight, or dry weight. Diameter and fresh weight are important in commerce, but dry weight is more important to the physiology of the tree.

Related Topics: CARBOHYDRATE PARTITIONING AND PLANT GROWTH; FLOWER BUD FORMATION, POLLINATION, AND FRUIT SET; LIGHT INTERCEPTION AND PHOTOSYNTHESIS; TEMPERATURE RELATIONS; WATER RELATIONS

SELECTED BIBLIOGRAPHY

Bollard, E. G. (1970). The physiology and nutrition of developing fruits. In Hulme, A. C. (ed.), The biochemistry of fruits and their products (pp. 387-425). London, England: Academic Press. Coombe, B. G. (1976). The development of fleshy fruits. Ann. Rev. Plant Physiol. 27:508-528.

DeJong, T. M. and J. Goudriaan (1989). Modeling peach fruit growth and carbohydrate requirements: Reevaluation of the double-sigmoid growth pattern. J. Amer. Soc. Hort. Sci. 114:800-804. Lakso, A. N., L. Corelli-Grappadelli, J. Barnard, and M. C. Goffinet (1995). An expolinear model of the growth pattern of the apple fruit. J. Hort. Sci. 70:389-394.

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