| 摘要： 本試驗利用溫室水耕栽培與盆植淹水兩種方式，來探討缺氧與淹水對番石榴與蓮霧葉片光合作用與植株生育的影響。在溫室水耕栽培系統，經由氧氣的調整，隨著根域環境溶氧值降低，葉片淨光合成作用、氣孔導度、細胞間隙二氧化碳濃度、蒸散作用以及葉片水份潛勢均顯著降低，也造成枝條以及新葉生長量減少，和葉片黃化脫落；在不同溶氧處理間，隨著氧氣量降低，番石榴花芽生成量減少，但蓮霧並無顯著差異。氣溫高於30℃，缺氧處理葉片溫度比氣溫高，但對照組則相反。蓮霧低氧處理植株，養液面環境乙烯濃度明顯較高。低氧或無氧下蓮霧均有皮孔、不定根形成，番石榴則無。兩者在無氧環境下均造成根系的嚴重傷害，在七十日以上的試驗期間，番石榴植株死亡率約38%，蓮霧則無植株死亡。在無氧環境下，番石榴根部元素濃度，一般較高，但葉片中氮濃度，則明顯隨著根域溶氧值降低而減少 在自然田間環境下，以盆植番石榴進行不同時期淹水處理，淹水後明顯降低番石榴的淨光合作用，並抑制植株生長，發生大量落葉。隨著淹水日數增加，根系傷害愈嚴重，排水後，淹水處理八日以下，成熟葉片光合作用有恢復的現象，淹水處理八日以上，則因葉片黃化脫落嚴重或植株死亡，而難以回復；在淹水處理三十日，有高達67%的植株死亡率。番石榴經淹水後，外觀仍有活性者，排水後亦能迅速產生新的枝梢，並發新根，恢復生長。The effects of hypoxia in root zone and flooding on the photosynthetic characteristic and growth of guava and waxapple were explored by hydroponic culture and pot flooding. In hydroponic culture with hypoxia in the root zone manipulated through different oxygen flow, net CO2-assimilation rate (Pn), stomatal conductance to water vapor (gs), intercellular CO2 concentration (Ci), transpiration rate (Tr) and leaf water potential (φleaf) were significantly decreased with decreasing dissolved O2 concentration (DO) from 7.0 to 0 ppm. Also, inhibition in shoot growth, leaf yellowing and leaf abscission increased with decreasing DO. Rate of flower formation decreased in guava but not in waxapple during hypoxic treatment period. As ambient air temperature higher than 30℃, temperature of the fully-aerated leaves was lower than the ambient temperature, whereas those of the hypoxic ones were higher than the ambient temperature. Concentration of ethylene in the headspace of hypoxic root zone was higher than the fully-aerated one. Under both hypoxic and anoxic condition, formation of hypertrophy lenticels and adventitious roots was enhanced in waxapple but nil in guava. Serious root injury was noted under anoxic condition in both fruit species. During 70 days of anoxic periods, 38% of guava plants died but none in waxapple. Mineral contents in the roots of anoxic plant were generally higher than in fully-aerated ones but the reverse was true for leaf nitrogen content. With flooding period varied from 5 to 30 days on potted guava plants, similar responses happened as those in hydroponic culture, i.e., After the drainage, those plants which had been flooded less than 8 days recovered in Pn, gs, Ci, Tr and φleaf. On the other hand, plants which had been flooded more than 8 days recovered insignificantly due to severe leaf abscission and plant death. The mortality reached 67% after 30 days of flooding. Guava plants which survived during flooding produced new leaf and new roots after drainage. |
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