Some morphological, anatomical, and physiological changes in the pear fruit (Pyrus communis var. Williams Bon Chrétien) during development and following harvest

Abstract

Morphological, anatomical, and physiological changes occurring in the developing fruit of Pyrus communis var. Williams Bon Chretien were studied at frequent intervals, from blossom until after commercial maturity, in three successive seasons. Morphological changes were shown by increase in measurements of volume, long and short axis, and the width of the cortex (flesh), the morphology of the fruit being interpreted by the receptacular theory, Anatomical changes were given by the duration and distribution of cell division, differentiation of tissues, cell size, and cell number. Physiological changes were expressed as changes in fresh weight, dry weight, and moisture content for the whole fruit, and separately for the flesh, peel, and core in the second and third seasons. Total and reducing sugars, starch, titratable acidity, and total and protein nitrogen were estimated per gram of dried flesh at each sampling. Respiration rates for whole fruit were measured by the Pettenkofer method. Physiological changes could not be expressed on a per cell basis because of the complex structure of pear tissue. Data presented on the basis of the number of days from blossom showed two distinct stages in fruit growth. Stage I, the first 42-56 days of development, corresponded to the main cell division period and was characterized by more rapid morphological but slower physiological changes (except for increase in protein nitrogen) than Stage 11, the remainder of the time on the tree. Comparable trends were found in the three seasons, but drought reduced growth rate in the first season. Some ripening changes were followed on removal from the tree and after periods of cold storage at 0°C.