POLYAMINES IN CHLORIDE-STRESSED CITRUS PLANTS - ALLEVIATION OF STRESSBY NITRATE SUPPLEMENTATION VIA IRRIGATION WATER

A study was conducted to elucidate the effects of chloride in the irri gation water on growth and development of two citrus rootstocks, 'Cleo patra' mandarin (Citrus reshni Hort. ex Tan) is salt tolerant and 'Tro yer' citrange (Poncirus x Citrus sinensis) is salt sensitive, Increasi ng chloride from 2 to 48 mM in the irrigation water resulted in increa sed leaf chloride levels, more severe damage of the leaves, and reduce d branch growth, High chloride in the irrigation water also caused inc reased putrescine (PUT) and decreased spermine (SPM) contents of the l eaves. These effects were slight in 'Cleopatra' but highly apparent in 'Troyer', The symptoms caused by high chloride were associated with h igh PUT and low SPM levels in the leaves. PUT may be involved in the d evelopment of chloride toxic symptoms, and SPM may protect or have no effect on chloride plant injury, The leaf polyamine profiles of 'Troye r' and 'Cleopatra' under nonstress chloride conditions were different, In 'Troyer' leaves, PUT level was 9-fold higher than in 'Cleopatra'; in 'Cleopatra' leaves, SPM level was 25-fold higher than in 'Troyer', Nitrate supplement to saline water reduced chloride accumulation in th e leaves and reduced the increase in PUT. The possible connection betw een ethylene production and PUT and SPM levels in the leaves of stress ed plants is discussed.