強制根圈通氣對兔眼藍莓(Vaccinium virgatum Ait.)植株浸水逆境後樹冠發展、葉片氣體交換及養分吸收之影響

Abstract

藍莓(Vaccinium spp.)要求保水性高但排水且通氣性亦佳的土壤。在亞熱帶地區夏季暴雨過後，田間短暫但頻繁的淹水問題會影響植株生育。根圈通氣可以立即改善土壤通氣性，但過度通氣可能改變土壤的氧化狀態和化學性質，從而影響土壤礦物質營養的可利用率和植株的生長。根圈通氣對藍莓植株生長的影響尚未有深入探討，因此本研究的目的為測試強制根圈通氣對盆植兔眼藍莓於浸水逆境後，植株樹冠發展、葉片氣體交換以及養分吸收的影響，以期作為藍莓植株在亞熱帶地區栽培管理之參考。試驗自2019年7月1日至10月29日進行，包含浸水和根圈通氣兩個變因。盆植‘NTU-104’兔眼藍莓分為正常灌溉及每日5小時浸水處理，處理後分別強制通氣0、3、6或12小時。試驗結果顯示，每日浸水處理結束後的淋洗作用導致栽培介質的pH值上升及EC值下降。浸水及強制通氣不影響植株枝條總長、葉片總數以及全株乾重，但浸水處理顯著降低植株平均單葉面積 (13.23 ± 0.40 cm^2) 和總葉面積 (3751.50 ± 184.88 cm^2)，而強制根圈通氣並無法緩解此負面影響。植株葉片氣體交換以及葉綠素相對含量(SPAD 值)不受浸水或根圈通氣影響。葉片中的巨量和微量元素濃度也不受任一處理影響，惟在正常灌溉條件下，植株根部鎂元素濃度因強制根圈通氣而顯著上升，浸水處理則顯著提高葉片和莖部中鈣元素的濃度。整體而言，強制根圈通氣並未有效減緩短期但頻繁浸水對兔眼藍莓植株營養生長所造成的影響。

Blueberry bushes (Vaccinium spp.) require moist but well-drained and aerated soil. Temporary but frequent waterlogging after heavy summer thunderstorm in the subtropics may affect plant growth. Forced rhizosphere ventilation (FRV) can instantly improve soil aeration but excessive ventilation may change soil oxidative status and chemical properties, thus affecting soil mineral nutrient availability and plant growth. However, the effects of excessive rhizosphere ventilation on blueberry bushes have yet to be thoroughly explored. Therefore, the objective of this study was to document the effects of FRV on canopy development, leaf gas exchange and nutrient uptake in rabbiteye blueberry (V. virgatum Ait.) bushes after waterlogging. The expected outcome will serve as a reference for cultivation and management of blueberry bushes in subtropics. The effects of FRV on blueberry growth after waterlogging was investigated from 1 July to 29 October 2019. Container grown ‘NTU-104’ rabbiteye blueberries were subjected to normal irrigation or 5-hour daily rhizosphere waterlogging. FRV was enforced inside the container for 0, 3, 6, or 12 hours every day after waterlogging treatments. Daily waterlogging increased medium pH but decreased medium EC due to leaching effect. Total lengths of shoots, leaf number and dry weight were not affected by either experiment variable. However, average leaf area (13.23 ± 0.40 cm^2) and total leaf area (3751.50 ± 184.88 cm^2) were significantly reduced by waterlogging and were not alleviated by FRV. Leaf gas exchange and SPAD values were not significantly affected by either irrigation or FRV. Macro- and micronutrient concentrations in leaves were also not significantly affected by either treatment. However, Mg concentrations in roots were significantly increased by FRV under normal irrigation condition while waterlogging significantly increased Ca concentrations in leaves and shoots. Overall, FRV had little effect on alleviating the impact of short-term but frequent waterlogging on vegetative growth in rabbiteye blueberry.