二氧化碳、氣溫及紫外線升高對作物生育及產量之影響

Abstract

近年來，CO2及CH4 等會發生溫室效應及其他足以破壞臭氧層的氣體排放量增加，使得地球氣候發生變化，紫外線增加。由於CO2 是光合作用的原料，故提高CO2濃度有助於增加光合速率，一般結果指出，提高CO2對提升作物乾物質累積及產量之效果以C4型較小，C3型較大，具有固氮能力的豆科作物之效果更大。但是高COZ 濃度尚會影響代謝、氣孔開度與密度、葉面積及其他性狀，故高CO2之效果隨實驗條件而異，結果也很分歧。如缺水、缺氮或葉片互相遮蔽時，都會降低CO2增加對作物之增產效果，而且不同溫度下CO2增加之效果亦不相同。近幾年在水稻之試驗結果顯示，群落狀態下，單純CO2倍增時，水稻生物量之增加率為24~40%間，稻穀增產率則為15~40%間，增產之原因多是穗數及稔實率增加所致，唯溫度增加時，對生物量沒有大影響，但稻穀產量則會因為稔實率降低而抵消了CO2倍增之效果。至於紫外線(UV-B)，現有結果已知其可影響多種植物之生理作用，而作物之葉綠素含量、葉分化、乾鮮重及產量均會受到影響。唯紫外線對水稻影響之結果也很分歧，需要更多的研究來說明。而且現已發現不同的品種間對UV-B有不同的抗性。對二氧化碳、氣溫及紫外線升高因應之道，除了可嘗試選育品種外，或可嘗試改善栽培法及改變栽植時期。 The effects of CO2 enrichment (EC), high temperature (HT) and ultraviolet on photosynthesis, biomass production and yield of crops are reviewed. Although many characteristics, such as metabolism, leaf area index, stomatal frequency and conductance, transpiration, etc., would be influenced by EC, HT and other conditions, the results are very variable due to the varied conditions in the field and greenhouse. In recent years, some experiments combined EC and HT in rice were investigated. The results indicated that the biomass production was markedly promoted by EC, and negligibly small affected by HT. On the contrary, the grain yield was 15- 40% higher in EC with low temperature, but remarkably reduced due to the high temperature induced sterility. Numerous studies have shown that ultraviolet-B (UV-B) can damage biologically important molecules in plants and has adverse effects on plants growth and yield. Growth and yield of rice was affected by UV-B and varied among cultivars. However, the results are variable among experiments. It requires more experiments carrying out under various climatic and solar UV-B regimes.