Relationship between the Occurrence of Hollowing in Watermelon and the Size and the Number of Fruit Cells and Intercellular Air Spaces.

Abstract

Hollowing (formation of a central cavity) in watermelons plagues the growers by reducing their market values. This paper reports the relationship between the occurrence of this disorder and fruit weight, cell size and number, and the volume of the intercellualr air spaces as by a) nodal position of the fruit, b) NAA application, and c) partial defoliation of the bearing. Fruits borne on the lower, basal nodes (Treatment L) were lighter at harvest than those borne on higher, distal nodes (Treatment H) but the former trended to develop hollowing, whereas the latter did not exhibit this physiological disorder. The basal fruits had fewer but larger cells through the transverse diameter than those of distal fruits ; they also had larger intercellular air spaces than the distal melons did. Fruits painted with NAA (Treatment N) and those on partially defoliated shoots (Treatment D) produced smaller melons having a small or no hollowing. Compared to the basal melons, the NAAtreated ones and those on defoliated shoots had proportionately less large cells and smaller intercellular air spaces. From these results, the following assumptions are drawn. The growth of cells in the inner region of basal fruits with its lower cell density cannot keep pace with the growth of the peripheral cells and of the rind having higher cell density. This differential growth causes cleavage to arise in the inner part of the fruit which gradually develops into a hollowing. When the growth of the fruit is suppressed by NAA or by defoliation, the cells in the inner region are able to grow as fast as those in and near the rind so that no stress is generated within the fruit. Conversely, when the number of cells per fruit is large, as it is in fruits on distal nodes, the growth of cells of the inner region keeps pace with that of the rind. Consequently, no internal strain ensues and no cavitation occurs.

Spatial accumulation pattern of citrulline and other nutrients in immature and mature watermelon fruits

“…38 Future research on the relationships between spatial/temporal patterns of citrulline accumulation and cell anatomy in watermelon fruits will be important to understand citrulline metabolism in watermelon. Hollowing (formation of a central cavity) in the fruits is another phenomenon commonly observed during watermelon maturation, 39 although cavity formation in mature fruits was not observed in the present study.…”

RAPID MESOCARP CELL ELONGATION ENHANCES GUMMING SYNDROME IN JAPANESE APRICOT (PRUNUS MUME SIEB. ET ZUCC.) FRUIT

“…Internal pressure during rapid fruit growth causes hollowing of the fruit flesh of tomatoes and watermelons (Kano 1993). In prune fruit, Sterling (1953) found that the formation of a gum duct was initiated during the rapid growth stage just before fruit maturation (Stage III).…”

Effects of Night-heating of Fruit on Cell Size and Sucrose Accumulation in the Outer Portion of Watermelon (Citrullus lanatus Matsum. et Nakai)

“…Optimum temperature for growth of watermelon is 25 to 30°C during the day and 16 to 20°C during the night (Saito, 1991). Cell division in watermelon fruit stops at 6 DAA (Kano, 1993). In this experiment, watermelon fruits were treated after 6 DAA.…”