釋氧物質與氯化鈣提升菊花對高溫短暫淹水之耐受性

Abstract

熱帶與亞熱帶地區之夏季高溫與豪雨造成土壤低氧，使露天栽培之菊花 [Dendranthema ×grandiflorum (Ramat.) Kitam.] 生長不佳或死亡。本研究探討高溫短暫淹水對菊花生長之影響，及釋氧物質 (Oxygen release compound, ORC) 與氯化鈣預處理對淹水耐受性不同之菊花光合作用、氧化逆境與抗氧化酵素生理反應等之影響。 高溫淹水3天時，部分參試菊花品種幼葉下垂，於莖基部產生不定根，但於回復正常澆、排水後隨即乾枯死亡。高溫淹水3天且回復正常澆、排水14天後，多數夏菊與秋冬菊品種之地上部生長減緩、株高較矮、葉片數較少及根部生長不佳。以根乾重減少比率評估所有參試品種中以‘黃精競’較耐高溫淹水逆境，而‘卡迪娜’為高溫淹水逆境敏感。 菊花‘黃精競’之淨光合作用速率 (Net photosynthesis rate, Pn)、氣孔導度 (Stomatal conductance) 及蒸散作用速率 (Transpiration rate)，於30/25 oC淹水第3天下降，但於回復正常澆、排水9天後Pn快速回升。而高溫淹水3天使不耐淹水‘卡迪娜’之Pn下降甚多，於高溫淹水前1天施用1 g•L-1 ORC處理可使‘卡迪娜’之株高、根乾重增加，較能維持固碳反應，因此Pn較淹水處理較高。 於30/25 oC下，淹水3天回復正常澆、排水之試驗期間，‘黃精競’之葉片過氧化氫 (Hygrogen peroxide, H2O2) 和丙二醛 (Malonialdehyde, MDA) 濃度變化不大，顯示氧化傷害不大，且葉片之過氧化氫酶 (Catalase, CAT)、抗壞血酸過氧化酶 (Ascorbate peroxidase, APX) 及榖胱甘肽還原酶 (Glutathion reductase, GR) 活性變化不大。而高溫淹水3天回復正常澆、排水後，不耐淹水‘卡迪娜’之葉片APX、GR活性增加，但葉片H2O2及MDA濃度大幅增加，無法降低氧化逆境之傷害；高溫淹水前施用1 g•L-1 ORC可提升‘卡迪娜’之葉片APX活性，減緩葉片H2O2累積，但葉片MDA濃度仍較高。 於高溫淹水前1及3天，分別澆灌0、60、90、120 mM氯化鈣於介質，對‘黃精競’之生長無顯著影響；而高溫淹水使‘卡迪娜’株高、總葉片數及根乾重，隨氯化鈣預處理濃度由0 mM提高至120 mM增加。於高溫淹水前進行120 mM氯化鈣預處理，可減緩淹水造成之根乾重下，降由80.9%降至42.2%。 高溫淹水前進行120 mM氯化鈣預處理，不影響‘黃精競’地上部生長、光合作用、氣孔導度、蒸散作用速率及細胞間隙二氧化碳濃度 (Intercellular CO2 concentration) 之變化，亦對葉片H2O2、MDA濃度、CAT、APX、GR活性無顯著影響。然而120 mM氯化鈣預處理，減緩淹水處理之‘卡迪娜’葉片MDA產生，於回復正常澆、排水後，維持其葉片CAT、APX、GR活性。

Heavy summer rain in subtropical and tropical areas causes soil hypoxia, resulting in poor growth or death of field-grown chrysanthemums [Dendranthema ×grandiflorum (Ramat.) Kitam.]. Growth responses to waterlogging were measured in chrysanthemum cultivars in this study. The effects of oxygen release compound (ORC) and CaCl2 pretreatments on growth, photosynthesis, oxidative stress, and antioxidant enzyme activities responses were studied in waterlogging-tolerant and intolerant cultivars subjected to short-term (3 days) waterlogging and high temperature (25-31 oC) conditions followed by the recovery (9-14 days). Three-day waterlogging caused wilting of young leaves and the formation of adventitious roots, which died soon after the recovery in many cultivars. Shoot growth, plant height, leaf number, and root growth in most cultivars reduced after 3-d waterlogging followed by 14-d recovery. Among the chrysamthemum cultivars tested,‘Huang Gin-Ging’is the most tolerant while‘Kaa Dei-Na’is the most sensitive to waterlogging, as shown by the reduction in root dry weight. Photosynthesis was measured in‘Huang Gin-Ging’and‘Kaa Dei-Na’, with control (without waterlogging), waterlogging (3-d waterlogging followed by 9-d recovery) and pretreatments with 1 g·L-1 ORC before waterlogging at 30/25 oC. In‘Huang Gin-Ging’net photosynthesis rate (Pn), stomatal conductance, and transpiration rate all decreased after 3-d waterlogging but recovered at 9-d recovery, regardless of ORC pretreatment. In contrast, 3-d waterlogging caused significicant decrease of Pn in‘Kaa Dei-Na’. Plants pretreated with ORC were taller, had more root dry weight, higher Pn and lower intercellular CO2 concentration (Ci), as compared to the waterlogged plants without ORC. Plants of‘Huang Gin-Ging’after 3-d waterlogging did not exhibit marked changes in leaf H2O2 and MDA concentrations, and CAT, APX, and GR activities at 30/25 oC. In contrast, waterlogged plants of‘Kaa Dei-Na’showed dramatic increase in leaf H2O2 and MDA concentrations, despite the higher APX and GR activities. Plants pretreated with 1 g·L-1 ORC could reduce leaf H2O2 concentration through early activated APX before waterlogging, while leaf MDA concentration was still high. Plant growth of 3-d waterlogged‘Hunag Gin-Ging’did not differ among pretreatments with 30 mL of 0, 60, 90, 120 mM CaCl2, while plants of‘Kaa Dei-Na’exhibited increased plant height, leaf number, and root dry weight as CaCl2 concentration increased from 0 to 120 mM. Application of 120 mM CaCl2 pretreatment alleviated waterlogging-injury of‘Kaa Dei-Na’through maintaining higher root dry weight (80.9% vs.42.2%). Shoot growth, photosynthetic parameters, H2O2, MDA, CAT, APX, GR did not differ in waterlogged‘Huang Gin-Ging’whether pretreated with 120 mM CaCl2 or not. However, plants of‘Kaa Dei-Na’pretreated with 120 mM CaCl2 had lower leaf MDA concentration and remained leaf CAT, APX, and GR activities after 9-d recovery.