Citrus Response to Salinity

Abstract

Citrus is among the most salt sensitive of horticulture crops. Growth and yield of citrus are seriously limited by salinity in many areas worldwide. Salt damage usually manifests as trees physiological disturbances and growth reduction. Factor affecting citrus response to salinity included salinity levels for onset and rate of yield decline in mature trees. The salinity is concerned with the regulation of chloride and sodium concentration in the leaves, stems and roots. The factors underlying changes in leaf gas exchanges parameters, reduction in growth and foliage damage at increasing salinity levels depended on scion-rootstock combination. Foliage damage as leaf burn and defoliation associated with accumulation of excess toxic levels of sodium and chloride in leaf cells. However, this problem can be minimized by using rootstocks that restrict the uptake of these ions. Genetic transformation methods have been applied in citrus to improvement salt-tolerance mechanism.柑桔是對鹽分敏感的園藝作物之一，在世界上有許多地區之柑桔生長及產量因鹽害而受到嚴重的限制。一般柑桔發生鹽害時常出現生理失調及生長遲緩的現象，其受害程度及降低之產量與鹽分濃度高低有關。植體的根、莖及葉內鹽害之發生與Na+及Cl-的調節及水分變化有關，利用適當接穗及砧木組合，可減緩鹽害所造成葉片氣體交換係數之改變、葉片生長遲緩及葉傷等現象。而葉傷的症狀，如葉燒及落葉之原因為葉片細胞累積過量的Na+及Cl-。不過該問題可藉由砧木的應用而限制離子之吸收加以改善，目前已有利用基因轉殖的方法促進柑桔對鹽害之忍受機制