缺水及鹽分對水稻生產之影響

Abstract

影響水稻產量的關鍵大致可歸納於：提高單位面積產量與擴展栽培面積。自綠色革命以來，水稻單位面積產量的變化已逐漸達到平峰，短期內難以突破，而地表仍有大面積土地，具有乾旱與鹽害問題。若能改進水稻耐旱耐鹽能力，則可利用這些土地生產，以增加水稻產量。缺水下水稻植株易表現出葉片捲曲、氣孔關閉等現象，而長期的鹽分處理則會造成，Na在葉片中累積，抑制光合作用，並加速葉片老化。水稻在生殖生長期對乾早與鹽分最為敏感，這些逆境均會傷害穗的發育，進而影響到開花與稔實率，降低總產量。水稻各品種耐鹽耐旱能力不同，抵抗這些逆境的機制可歸納為：（一）調整生育時期以逃避乾早。（二）改變植物體結構，提高用水效率。（三）調節細胞內滲透壓。（四）有效解除離子毒害。這些抗性的機制是透過多基因的作用，並參與複雜的生理反應，故以過去的育種方法所得成果有限。現在可以利用分子生物技術，建立基因輿圖，定位出與耐旱耐鹽有關的量性狀基因座，則可望突破這些限制。近年來也有不少研究，以粒子槍射擊法或農桿菌汰等基因轉殖技術，獲得高效率的轉植水稻。期望能將陸續發現的耐旱耐鹽基因轉入水稻中，以增強水稻的抗逆境能力。 Drought and salt stress are two major constraints to rice production and yield stability in many regions on earth. In general, rolled leaves and closed stomata were easily found under drought stress. Accumulation of Na, decreasing of photosynthesis and enhancing of senescence were also found when plants were subjected to salt stress. Rice plant is most sensitive to both stress during reproductive stage. Loss of grain set and yield is tightly associated with the failure of panicle to exsert from the flag leaf, the reduced floret number and the lower pollen fertility. Several drought / salt-resistance mechanisms have been identified for rice: (1) drought escape via appropriate phenology, (2) moderated water-use through morphological changes, (3) the capacity for osmotic adjustment, and (4) efficiently devoid the ion toxicity. In the past, the breeding for both stress tolerance was slowly progressed because the complexity and the involvement of multi genes in drought / salt-resistance. However, recent development of molecular linkage markers for root traits and osmotic adjustment as well as transgenic techniques offer new opportunities for drought I salt-resistance breeding.