甜菜鹼與幾丁質對萵苣和玉米水分利用效率之影響

Abstract

受氣候變遷和全球暖化的影響，臺灣近年降雨次數變少，乾旱頻率與時間都增加，台灣農業用水占整體年需水量之70%，未來可能面臨更多缺水壓力。控制田間容水量(field capacity, FC)與施用生物刺激劑(biostimulants)被認為是可以提升農業用水灌溉效率的方式。本研究探討萵苣和玉米等蔬菜作物，在控制灌溉方式下搭配施用生物刺激劑以達到省水或提升產量的可行性。 生物刺激劑屬天然成分及植物和微生物的代謝物，僅影響農作物本身，不傷害環境。本試驗藉由添加被認為具有對抗非生物逆境的功能的甜菜鹼(betaine)與幾丁質(chitin)，探討福山半結球型萵苣(Lactuca sativum var. capitata)和玉米‘玉美珍’ (Zea mays ‘White Pearl’) 在正常給水(normal irrigation)和調缺灌溉(regulated deficit irrigation, RDI)下生物刺激劑對其生長和水分利用效率(water use efficiency, WUE)之影響。 結果顯示：在調缺灌溉下噴施50 mM甜菜鹼的萵苣，葉面積較調缺灌溉下未施用甜菜鹼的處理顯著增加48.5%，其產量與對照組沒有顯著差異但節省53.5%的灌溉水，使產量水分利用效率(WUEyield)提升1.1倍；正常給水下噴施50 mM甜菜鹼的萵苣淨光合作用速率提升，產量比對照組多21.6%，但未達顯著差異，且較對照組減少12.7%灌溉水量。玉米在調缺灌溉下噴施100 mM的甜菜鹼，株高、葉面積和產量與對照組無顯著差異，但可節省78.1%的灌溉水；在正常給水下噴施100 mM甜菜鹼可減少17.3%灌溉水量，產量比對照組多20.9%，但未達顯著差異。因此認為甜菜鹼可提升淨光合作用速率並維持光合作用所需之蒸散作用速率，在作物缺水時穩定其生長，維持或增加產量及水分利用效率，在正常給水下也可增加淨光合作用速率提高產量。 萵苣在調缺灌溉下施用2 g/Kg的幾丁質，葉面積較對照組顯著增加25.6%，地下部鮮重顯著提升，產量與對照組無顯著差異，但節省48.3%的灌溉水，WUEyield比對照組增加1.3倍；正常給水下施用4 g/Kg的幾丁質，株高顯著提高，葉面積比對照組顯著增加62.8%，減少8.8%灌溉水量、顯著增產83.6%，淨光合作用速率提高，葉片水分利用效率(WUEi)、WUEyield和乾物重水分效率(WUEbiomass)都較對照組高；玉米在調缺灌溉下施用2 g/Kg的幾丁質，株高、葉面積、果實產量和葉綠素計讀值(chlorophyll meter reading, CMR, SPAD-value)皆顯著高於對照組，節省84.8%的灌溉水並比對照組顯著增加2.3倍的產量；玉米在正常給水下施用4 g/Kg的幾丁質，使葉面積顯著提升，較對照組減少31.1%灌溉水量並顯著增產2.5倍，且比對照組有更高的水分利用效率(WUEi、WUEyield和WUEbiomass)。因此認為幾丁質可促進根系發展，使作物吸收水分能力增強，且增加葉片淨光合作用速率，使作物水分利用效率提升。 萵苣在調缺灌溉下複合施用50 mM甜菜鹼和2 g/Kg的幾丁質，葉面積、產量、乾物重和淨光合作用速率皆較對照組有提升，然結果並未比單獨施用甜菜鹼或幾丁質有更顯著的提升，玉米在調缺灌溉下複合施用100 mM甜菜鹼和2 g/Kg的幾丁質也有相似結果。 綜上所述，施用甜菜鹼和幾丁質，可穩定萵苣和玉米在調缺灌溉下的生長，提升缺水時的產量，在減少灌溉量下提升水分利用效率，達到省水並提高產量的效果。

Affected by climate change and global warming, Taiwan's rainfall has decreased and the frequency and period of drought have increased in recent years. In Taiwan, agricultural water demand accounts for 70% of the total annual water demand. Water shortage pressure may become serious in the future. Controlling field capacity (FC) and the application of biostimulants are considered to be the ways to increase the efficiency of agricultural water irrigation. This study access the feasibility of using biostimulants to save water and increase yields in vegetable crops such as lettuce (Lactuca sativum var. capitata) and maize (Zea mays ‘White Pearl’). Biostimulants are natural constituents and metabolites of plants and microorganisms that affect the crop itself and do not harm to the environment. The effects of betaine and chitin, which are thought to have a function against abiotic stress, on the growth and water use efficiency (WUE) of Lactuca sativum var. capitata and Zea mays ‘White Pearl’ under normal irrigation and regulated deficit irrigation (RDI) were investigated. The results showed that the leaf area of lettuce which sprayed with 50 mM betaine under RDI significant increase of 48.5% that compared with the lettuce which sprayed 0 mM betaine under RDI. The yield of lettuce did not different with the control but saved 53.5% of the irrigation water. Thus, the yield of water used efficiency (WUEyield) increased by 1.1 times. The lettuce which sprayed with 50 mM betaine under normal irrigation had increased the net photosynthesis rate and decrease 12.7% of irrigation water compared with the control. The yield increased 21.6% than the control, but there was no significant difference. Maize sprayed with 100 mM betaine under RDI which the plant height, leaf area and yield were not significantly different with the control but save 78.1% of irrigation water. Maize sprayed with 100 mM betaine under normal irrigation which the yield was not significantly different with the control but 20.9% more and reduced 17.3% of irrigation water. The results showed that betaine could increase net photosynthesis rate and maintain transpiration rate required for photosynthesis. It could stabilize plants growth, maintain or increase yield and WUE when crops facing water shortage, even under normal irrigation. After treated with 2 g/Kg of chitin under RDI, lettuce leaf area increased significantly by 25.6% compared with the control. The root fresh weight showed a significant increase. Besides, it could save 48.3% of the irrigation water, the yield was not significantly different from the contro. WUEyield increased 1.3 times comparing with the control. Lettuce which applied 4 g/Kg of chitin under normal irrigation had significantly increased plant height and 62.8% of leaf area comparing with the control. It decreased 8.8% of irrigation water and increased 83.6% of the yield , and also promoted photosynthesis rate. Water used efficiency (WUEi), WUEyield and biomass of water used efficiency (WUEbiomass) of leaf were all higher than the control. Maize which applied 2 g/Kg of chitin under RDI, its plant height, leaf area, fruit and chlorophyll meter reading (CMR, SPAD values) were significantly higher than control. It saved 84.8% of irrigation water and the yield rose 2.3 times than control. Maize which applied 4 g/Kg of chitin under normal irrigation, its leaf area was significantly increased. It saved 31.1% of irrigation water and the yield was 2.5 times higher than control. All of water used efficiency (WUEi, WUEyield and WUEbiomass) were higher than control. The results indicated that chitin could promote the development of root system, enhance the water absorb capacity of crops and net photosynthesis rate of leaves, which improved crops WUE. Compared with the contro, lettuce which was applied 50 mM betaine and 2 g/Kg chitin under RDI could improve leaf area, yield, biomass and net photosynthesis rate. However, the results were not better than the treatments with only betaine or chitin. Maize which was applied 100 mM betaine and 2 g/Kg of chitin under RDI also showed similar results. In summary, the application of betaine and chitin could stabilize the growth of lettuce and maize under RDI. Betaine and chitin increased the yield when the water shortage and improve the WUE under RDI to achieve the effects of saving water and increasing production.