Grafted Melons Irrigated with Fresh or Effluent Water Tolerate Excess Boron

Abstract

The effects of boron and effluent (treated sewage water) on vegetative growth, fruit yield, and boron uptake of grafted and nongrafted melons (Cucumis melo L. cv. Arava) were studied. Nongrafted melon plants and melon plants grafted onto the commercial Cucurbita maxima Duchesne × Cucurbita moschata Duchesne rootstock ‘TZ-148’ were grown in pots filled with perlite in a heated greenhouse and were irrigated with fresh water or effluent. The two irrigation waters contained boron in five concentrations ranging from 0.1 to 10.4 mg·L−1. The boron concentration in the plants increased linearly with that in the irrigation water. The highest boron concentrations were found in old leaves, the lowest in the fruit, and intermediate concentrations were noted in the roots. The boron concentrations were, in general, significantly lower in grafted than nongrafted plants, possibly because the root system of the former had higher selectivity and lower boron absorption than that of the latter. Fruit yield and dry weight accumulation in shoots and roots decreased linearly as the boron concentration in the irrigation water increased, the nongrafted plants were more sensitive than grafted ones to the boron level, and both were more sensitive under fresh water irrigation than under effluent irrigation. It is suggested that the higher boron sensitivity of the root systems of the nongrafted plants probably decreased their capability to absorb water and nutrients, which in turn sharply reduced their fruit yields.