Abstract
Melon (Cucumis melo L. group) plants of two resistant lines and one susceptible line to viviparous sprouting were grown with three different concentrations (2.4, 4.2, and 6.0 me·L−1) of potassium to investigate the relationship between viviparous sprouting and endogenous abscisic acid (ABA). Seed yield per fruit was considerably decreased with decreasing potassium application in the susceptible line. In the resistant line, however, no influence on seed yield was observed. Potassium concentrations both in the petiole and in the juice around the placenta were higher in the resistant line than in the susceptible lines. Vivipary increased with decreasing concentration of potassium applied to the susceptible lines. No viviparous sprouting was observed in any potassium treatments for the resistant line. ABA content in the fruit juice decreased with decreasing potassium concentration. A germination test was carried out with different concentrations of ABA, and resulted in sharp decline of seed germination with increasing ABA concentrations in the resistant line. These results suggest that lower potassium application may cause a decreased ABA content in fruit juice, may cause a increase of viviparous sprouting in the fruit, and that the resistant line showed an inhibitory effect of ABA on sprouting at a lower threshold value of ABA concentration.
