土壤水分條件影響芒果生理特性之研究

Studies on Physiological Characteristics of Non-Bearing Mango (Mangifera indica, L.) Trees as Affected by Soil Moisture Conditions

盆栽愛文芒果樹以PVF式自動吸水裝置，設定土壤含水量為土壤最大含水量之30%、45%、60%及75%，亦即土壤水分潛勢為-0.95MPa、-0.55MPa、-0.35MPa及可0.25MPa等四種處理，以研究土壤水分與芒果樹植株生長之關係。試驗期間自民關78年4月至10月，為台灣夏季高溫期，結果發現土壤水分嚴重影響芒果樹之生長，如土壤水分潛勢為-0.95MPa時，芒果樹之植株比其他較高土壤水分潛勢的芒果植株，減少抽梢2次，樹幹直徑生長（肥大生長）較小，吸水量較低且因氣孔開孔活躍性較低，故蒸散率亦較低；但不影響葉數、葉面積及每段枝梢的長度。植株如生長於-0.55MPa、-0.35MPa、及-0.25MPa等較高土壤水分潛勢時，除了-0.55MPa有較大的樹幹直徑生長，較高的生物量及較低的需水量外，其餘生長特性如抽梢次數及長度、葉數與葉面積、吸水量、蒸散率、氣孔開孔活躍性等，均未隨著土壤水分潛勢的增加而增高，顯然芒果樹生長最適合之土壤水分潛勢為明0.55MPa。此外芒果樹的凋萎點約在葉片水分潛勢-2.0MPa，亦即土壤含水量7%附近。又調查資料顯示，地溫在四種不同土壤水分潛勢處理時差異極小，並非生長之限制因子。

One-year grafted mango (Mangifera indica L.) seedling (cv. Irwin/Native) were growing in 20 liter containners with the medium of sandy loam soil. The soil moisture conditions were divided into -0.95MPa, -0.55MPa, -0.35MPa and 0.25Mpa of soil water potentials, respectively, which were controlled by different height of PVF (polyvinyl formate) strips. Continuous surveys were conducted during the hot summer season from April to October 1989 to evaluate the plant growth and water relations. The plants growing m the -0.95MPa of soil water potential (SWP) showed much less in diameter growth of trunk than growing in the other higher SWP. Meanwhile, the number of shooting was also reduced two times in the -0.95MP SWP. Owing to the weak activity of stomatal aperature of the plant in the -0.95MPa SWP, the water absorption rate and transpiration rate decreased significantly than others. However, the number of leaves, leaf area and length of shoot were not affected by these different treatments of soil water potentials. In the higher soil moisture conditions, -0.55MPa, -0.35Mpa and -0.25MPa SWP included, the number of shooting, shoot length, number of leaves, leaf area, water absorption rate, transpiration rate and activity of stomatal aperature were not increased with increasing soil water potentials, however the plants growing in the -0.55MPa SWP had the characteristics of higher diameter growth of trunk and biomass and lower water requirement. Apparently -0.55MPa SWP is the most suitable soil water potential for mango growth. The wilting point and the change of soil temperature of potted mango trees will also be discussed.