蕹菜與葉用甘藷之防寒研究

Abstract

寒害為低溫引起之非生物性逆境，抑制許多熱帶與亞熱帶作物之生長與發育。蕹菜 (water convolvulus or water spinch; Ipomoea aquatica Forsk.) 與葉用甘藷 (leafy sweetpotato; Ipomoea batatas (L.) Lam.) 皆為暖季蔬菜，耐寒力弱。本研究共進行四個試驗，預試驗希望瞭解低溫逆境對蕹菜與葉用甘藷植株外觀與生理反應之影響，試驗一至三透過設施、調控養液鈣與磷濃度及葉面施用鈣與磷等方式，希望找到減緩寒害之最適處理。預試驗結果顯示低溫會抑制蕹菜生長，並引起蕹菜與葉用甘藷的氧化逆境。試驗一結果說明不織布覆蓋可提供保護以防止寒害，故蕹菜含水量比未覆蓋之對照組佳；簡易隧道棚比對照組具有較高的土溫，但不影響蕹菜與葉用甘藷園藝性狀；25℃溫水滴灌對兩種蔬菜的耐寒性幾乎沒有益處。試驗二中，將養液鈣濃度由 2.5 mM 提高至 3.125 mM 可顯著提高低溫後蕹菜之含水量，降低過氧化氫與丙二醛濃度；將養液磷濃度由 500 μM 提高至 750 μM 可減緩低溫造成蕹菜之含水量下降，並降低丙二醛濃度。葉用甘藷不適合以調整養液鈣濃度的方式減緩寒害；但生長在 1000 μM 磷之養液中，植株耐寒性較佳，除了可減少低溫對地上部造成之生長抑制，低溫後也可維持較高之葉片葉綠素含量及含水量。試驗三結果顯示低溫前葉片預施鈣與磷無助於蕹菜與葉用甘藷之耐寒性。綜上所述，蕹菜較適合以不織布覆蓋、調整養液鈣濃度至 3.125 mM 或調整養液磷濃度至 750 μM 等方式來減緩寒害；葉用甘藷則推薦以不織布覆蓋或調整養液磷濃度至 1000 μM 來減緩低溫傷害。

Chilling is an abiotic stress caused by low temperature that results in inhibition of growth and development in many tropical and subtropical crops. Water convolvulus (Ipomoea aquatica Forsk.) and leafy sweetpotato (Ipomoea batatas (L.) Lam.) are both warm-season vegetables and have little tolerance toward low tempersture. Four experiments were conducted in this research. Pre-experiment aims to investigate the effects of low temperature on appearance and physiological responses of water convolvulus and leafy sweetpotato. Experiment I to III are intend to identify the most appropriate ways that can mitigate the chilling injury of water convolvulus and leafy sweetpotato through protection facility, regulating of calcium and phosphorus concentration in nutrient solution and leaf spray of calcium and phosphorus. The results in pre-experiment showed that low temperature inhibits the growth of water convolvulus, and causes oxidative stress in water convolvulus and leaf sweetpotato. The results in experiment I showed that water convolvulus with non-woven floating cover provided protection against chilling and thus had better water content than the uncovered control. Row cover provided higher soil temperature than the uncovered control, but had no effect on the horticultural characters of water convolvulus and leafy sweetpotato. Drip irrigation with 25℃ water had little benefit to cold resistance of both vegetables. In experiment II, raising the calcium concentration of nutrient solution from 2.5 mM to 3.125 mM can significantly increase the water content of water convolvulus after low temperature, and decrease the concentration of hydrogen peroxide and malondialdehyde (MDA). Increasing the phosphorus concentration of nutrient solution from 500 μM to 750 μM can reduce the decrease in water content of water convolvulus caused by low temperature and decrease the concentration of MDA. Regulating of calcium concentration in nutrient solution was unsuitable to alleviate the chilling injury on leafy sweetpotato. But plants grown in nutrient solution with 1000 μM of phosphorus have better cold resistance, which can reduced the growth inhibition caused by low temperature on the shoot, and maintain higher chlorophyll content and water content after low temperature. The results in experiment III showed that leaf spray of calcium and phosphorus before low temperature had no obvious effect on increasing the cold resistance of water convolvulus and leafy sweetpotato. In summary, water convolvulus is more suitable for non-woven floating cover, adjust the calcium concentration in nutrient solution to 3.125 mM or adjust the phosphorus concentration in nutrient solution to 750 μM to reduce the chilling injury. For leafy sweetpotato, it is recommended to use non-woven floating cover or adjust the phosphorus concentration in nutrient solution to 1000 μM to reduce the damage caused by low temperature.