Salt Tolerance of Muskmelons as Affected by Diluted Sea Water Applied at Different Growth Stages in Nutrient Solution Culture

Abstract

Muskmelons (Cucumis melo L.) were grown with nutrient solutions to examine the effect of stage and duration of exposure to diluted sea water treatments at stage I (transplanting to pollination), stage II (pollination to fruit net development) and/or stage III (fruit net development to harvest) on the growth at harvest in experiment I and the growth at the end of three stages in experiment II.
Experiment I Whole plant dry weight and fruit fresh weight tended to increase with reduced exposure to diluted sea water and to decrease with increased sea water concentrations. Fruit fresh weight increased and Cl and Na contents in leaves remained unaffected when plants grown in diluted sea water at stage I were grown in base nutrient solution at stages II and III. The shorter the duration of the treatments the lower the Cl and Na contents in leaves.
Experiment II The deleterious effect of treatment solution on growth generally decreased with plant age and reduced exposure to treatment solution. The exposure to treatment solution at stage III reduced whole plant dry weight and fruit fresh weight, but did not affect leaf+stem+root dry weight. Saltiness in fruit increased with longer exposure. Cl and Na contents in leaves at harvest were significantly higher when exposed to treatment solution at stage III. Osmotic potential of leaves was proportional to that of the nutrient solution at each stage.
As a result, early stage till pollination and fruit development stages were most sensitive to saline conditions when whole plant dry weight, and fruit fresh weight and quality of muskmelons were used as index of salt tolerance, respectively.