菊花耐淹水指標與水分生理

Abstract

菊花在臺灣大多以露天栽培，然而梅雨和颱風豪雨造成田間淹水，易導致菊花死亡，嚴重影響產量。本研究探討臺灣菊花品種在模擬夏季高溫淹水和回復正常澆水後之生長與生理反應差異性，進而選拔出較耐淹水之商業品種，並找出快速、可靠之耐淹水性指標，以利未來耐淹水育種之用。除了極端之淹水逆境，合理化的土壤水分管理有助於菊花產量和品質的提升，本研究亦探討菊花不同生長時期最適合的土壤含水量範圍。 高溫淹水三天即造成參試21個菊花品種生長受影響，根莖葉乾重、株高、葉片大小和葉數減小，且新生葉片黃化，但不同品種受淹水減少生長的程度不同。菊花之高溫淹水耐受性具有品種間差異，淹水三天及缺氧逆境10天處理下，‘F15’和‘雙色紅’皆生長良好，‘花御殿’和‘青心黃’之生長則明顯受影響。 淹水三天後，‘F15’和‘雙色紅’之光合作用、氣孔導度和蒸散速率下降幅度小於不耐淹水之 ‘花御殿’ 和 ‘青心黃’，且回復正常澆水後，其光合作用迅速回升。較不耐淹水之‘花御殿’ 和 ‘青心黃’不僅於淹水期間，光合作用、氣孔導度和蒸散速率大幅降低，回復正常澆水後，氣孔導度和光合作用仍低，但細胞間隙CO2濃度升高，顯示除氣孔因素之外，羧化代謝受限制之非氣孔因素亦導致光合作用能力下降。試驗期間菊花各品種葉片之Fv/Fm無明顯下降，顯示葉綠素螢光可能非為菊花耐淹水性之良好指標。淹水三天後，不耐淹水 ‘青心黃’ 嫁接於耐淹水 ‘F15’根砧處理之氣孔導度、光合作用和蒸散速率回升現象高於‘F15’嫁接於 ‘青心黃’根砧處理，可見主要決定菊花淹水耐受性主要來自根部表現而非地上部。 淹水三天回復正常澆水後，較耐淹水 ‘F15’ 和 ‘雙色紅’ 葉片H2O2和丙二醛 (Malondialdehyde, MDA) 濃度無大量增加，超氧歧化酶 (Superoxide dismutase, SOD) 活性升高。不耐淹水之‘花御殿’和‘青心黃’ 葉片H2O2和MDA大量累積，‘花御殿’之SOD、過氧化氫酶 (Catalase, CAT)、抗壞血酸過氧化酶 (Ascorbate peroxidase) 和榖胱甘肽還原酶 (Glutathion reductase, GR) 活性無上升，‘青心黃’之SOD、CAT和GR活性雖有提升，仍無法有效清除過量之自由基。 利用土壤含水量測定儀WET Sensor和WaterScout SM100可制定良好菊花灌溉標準，兩儀器與重量法進行迴歸皆為直線相關 (R2=0.89、R2=0.95)。以WET監測為51%含水量下，菊花具最高光合作用速率，且光合作用下降早於葉片水勢，顯示缺水下光合作用表現較葉片水勢敏感。可見花苞前栽培以SM100監測為平均30%含水量下，菊花株高、莖粗、葉數和葉面積生長快速。栽培於平均50%含水量之過量澆灌下，不耐淹水菊花品種萎凋死亡；低於平均20%含水量之限水灌溉，植株因生長減緩而延遲到花天數且花徑減小。不同菊花品種耐旱性相異，其中 ‘青心黃’ 隨著土壤含水量下降，氣孔導度和生長速率下降幅度最大，為參試四品種中最不耐旱。 菊花四品種於可見花苞後以SM100監測為平均14%和22%含水量之限水澆灌下，不會影響花朵顯色時間以及開花採收所需日數，採收時花徑、主花序梗長和顯色花數減少，但瓶插時期花徑增加比率較大，且花朵開放數與平均40%和55%含水量處理無差異。限水澆灌下，瓶插前期鮮重增加量較多且瓶插後期鮮重減少量較小，此因瓶插時期切花之氣孔導度和蒸散速率較小，導致植體較不易失水。不過，可見花苞後不同含水量處理對四品種菊花瓶插壽命影響不大。 綜上所述，測量淹水逆境下菊花光合作用下降幅度、H2O2和MDA累積情形，以及回復正常澆水後光合作用回升趨勢和細胞間隙CO2濃度有無大幅升高，可作為品種耐淹水性之良好指標。不耐淹水 ‘花御殿’ 和 ‘青心黃’ 於高溫淹水三天期間，葉片氣孔導度下降，導致光合作用速率下降，且H2O2和MDA大量累積；回復正常澆水後，除了氣孔因素外，羧化代謝受限制亦減少光合作用進行，且H2O2和MDA累積加劇。耐淹水 ‘F15’ 和 ‘雙色紅’ 於淹水期間氣孔因素降低光合作用進行，但逆境解除後氣孔導度和光合作用迅速回升。菊花水分管理上，於可見花苞前以SM100量測平均含水量50%之過量澆灌處理亦會使不耐淹水品種遭受淹水逆境。參試四品種菊花栽培於平均含水量30%，生長快速且不遭受淹水及缺水逆境。而菊花於可見花苞後則可維持平均含水量14%-22%之限水澆灌，以利切花水分平衡。

Chrysanthemum [Dendranthema ×grandiflorum (Ramat.) Kitam.] is majorly cultivated in the field in Taiwan. Heavy rain may result in waterlogging, which affects plant growth and yield. It is vital to determine growth and physiological responses to flooding of chrysanthemum cultivars and to establish the criteria for the breeding or selection of waterlogging tolerant chrysanthemum cultivars. The results in chapter 3 experiment 1 showed that 3 days short-term waterlogging caused growth reduction of 21 chrysanthemum cultivars. Root and shoot weights, plant heights, leaf sizes, and leaf number were reduced, together with chlorosis in recently fully developed leaves on 14 days after the waterlogging treatment. Among the chrysanthemum cultivars tested, ‘F15’ and ‘Remix’ grew well either after a 3-day waterlogging or a 10-day hypoxia. Three-day waterlogging followed by 7-day recovery in chapter 4 experiment 1 showed that stomatal conductance and net photosynthesis reduced more in ‘Hua-Yu-Dieng’ and ‘Regatta’ than in ‘F15’ and ‘Remix’. After 1-day drainage, stomatal conductance and photosynthesis recovered in ‘F15’ and ‘Remix’. The concomitant increase in intercellular space CO2 concentration and the decrease in stomatal conductance and net photosynthesis after drainage of ‘Hua-Yu-Dieng’ and ‘Regatta’ suggested that waterlogging not only reduced stomatal conductance but also caused carboxylation limitation. No significant decrease in the maximal quantum yield of photosystem II photochemistry (Fv/Fm) after waterlogging in the four tested cultivars. The waterlogging-intolerant ‘Regatta’ grafted on tolerant ‘F15’ rootstock resulted in increased photosynthesis after waterlogging, suggesting that waterlogging tolerance is closely related to root performance. Three-day waterlogging followed by 6-day recovery in chapter 5 showed that H2O2 and MDA concentrations remained unchanged in ‘F15’ and ‘Remix’, but increased in ‘Hua-Yu-Dieng’ and ‘Regatta’. H2O2 and MDA concentrations in leaves could be reliable makers for evaluating the waterlogging tolerance of chrysanthemum cultivars. The activities of SOD, CAT, APX, and GR were unaffected after waterlogging in ‘Hua-Yu-Dieng’. ‘Regatta’ had higher but appeared insufficient of SOD, CAT, and GR activities after waterlogging, because H2O2 and MDA concentrations still increased. Linear relationships were found between measurements of WET and SM100, and with gravimetric method, indicating that using WET Sensor (WET) and WaterScout SM100 (SM100) soil moisture sensors to measure volumetric water contents (VWC) would facilate irrigation management. Plants had the highest net photosynthesis rate when grown at 50% VWC as measured with WET. Drought reduced photosynthesis rate earlier than the leaf water potential, suggesting that measurement of photosynthesis was more sensitive than that of leaf water potential. Before visible floral bud stage, chrysanthemum grew well at 30% VWC as measured with SM100. Waterlogging-intolerant cultivars wilted when grown with higher VWC (50% measured with SM100). Lower VWC (below 20% measured with SM100) resulted in reduced plants growth and inflorescence diameter. Stomata conductance and growth were reduced more in ‘Regatta’ than in ‘F15’, ‘Remix’, and ‘Hua-Yu-Dieng’. Deficit irrigation (14%-22% VWC) after visible floral bud stage did not alter time to anthesis, although plants had smaller inflorescences diameter and shorter main peduncle length at harvest. Well irrigated (40%-55% VWC) plants exhibited increases in inflorescence diameter and number of opened inflorescence during vase life. Plants grown under deficit irrigation after visible floral bud stage had cut flowers with lower stomatal conductance and transpiration rate, which led to better water balance and delayed water loss. However, different irrigation treatments after visible floral bud stage did not affect the vase life of the cultivars tested. In waterlogging-intolerant cultivars, stomatal conductance and net photosynthesis reduced during waterlogging together with accumulation of H2O2 and MDA in leaves. After drainage, intolerant cultivars exhibited stomatal closure and carboxylation limitation. In contrast, waterlogging-tolerant cultivars showed recovery of stomatal conductance and photosynthesis after drainage. The waterlogging-intolerant cultivars did not grow well when grown under 50% VWC, as measured with SM100. Plant grew faster under well irrigated (30% VWC measured with SM100) before visible floral bud stage than those under 20% VWC. Reduced irrigation to 14%-22% VWC as measured with SM100 after visible floral bud stage resulted in cut flowers with delayed water loss.