Water stress and leaf necrosis symptom of rambutan seedlings ( Nephelium lappaceum Linn.)

N. C. Wong and R. Nadeson

Abstract

Rambutan trees ( Nephelium lappaceum Linn.) experience leaf scorchings on the lower branches, particularly in areas with a distinct dry season. Glasshouse experiments were conducted to investigate the causes of this scorching phenomenon. The experiments were conducted using a completely random design with varying watering regimes as treatments on rambutan seedlings. When soil moisture content was reduced gradually to below 20.0% by weight, signs of leaf scorching were observed on these seedlings within 3 weeks. By the sixth week when the soil moisture content was further decreased to less than 15.0%, severe leaf scorchings developed. At the 10th week, leaf scorchings were very prominent when soil moisture content was below 14.0%. The leaf area affected by scorching was significantly correlated with the soil moisture content. In addition, the affected rambutan seedlings exhibited apical small leaf characteristics and that no new shoot emerged. Moisture stress had been shown to cause leaf necrosis in rambutan seedlings. This was confirmed when necrotic seedlings recovered rapidly upon rewatering. Subsequently, no further leaf scorching was observed. New shoots and leaves emerged which proceeded to develop normally.

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