鵲豆在輕度高溫下之生理反應及耐熱指標

Abstract

鵲豆可用於蔬菜、雜糧、覆蓋作物等多重用途，同時對乾旱逆境耐受性高，在未來極端氣候中具有持續穩定供應糧食之潛力。為了確認鵲豆高溫下之生理反應，以應用於後續選育工作，本研究首先選出可於夏季花芽分化之日長不敏感鵲豆種原，接著調查所選出之農業試驗所9項種原於35°C輕度高溫中生長狀況，綜合評估株高、葉面積與乾重三項生長指標，選取L3、L19兩項為熱敏感品系及L12、L14兩項為耐熱品系，並測定生理反應指標。鵲豆苗期淨光合作用於35°C處理1天後效率皆提升，氣孔導度及蒸散作用提升指出鵲豆可能透過此路徑降低高溫傷害，光合作用系統二最大光效能(Fv/Fm)於熱敏感品系中未顯著變化，耐熱品系則於高溫後Fv/Fm輕微下降、非光化學淬熄係數(qN)上升，顯示光合作用系統二有受損情形，並透過熱能逸散出多餘能量。高溫後耐熱品系L12及L14丙二醛含量累積量較低，顯示氧化逆境在耐熱品系中較為輕微，抗氧化酵素抗壞血酸過氧化酶及過氧化氫酶於高溫處理後活性皆被誘導，而過氧化酶活性及脯胺酸含量高溫後皆未顯著變化。為建立快速評估耐熱性之方法，利用離體葉片進30°C至60°C高溫處理，觀察細胞膜熱穩定度與葉綠素螢光表現之變化，並比對半致死溫度與生長指標變化量之相關性，葉綠素螢光表現與各項生長指標均屬於低度相關，細胞膜熱穩定度之半致死溫度與葉面積變化具中等相關性。結果顯示丙二醛與離體葉片之細胞膜熱穩定度表現，與耐熱性相關性較高，可做為未來耐熱選拔之指標。

Lablab bean is a multipurpose crop, that is used as vegetable, pulse and covered crop. Apart from various uses, lablab bean has great tolerance to drought, having potential to stabilize food production under extreme climate. In this study, light period insensitive accessions which is capable to differentiate flower bud under summer were selected. Growth of nine selected accessions from Taiwan Agricultural Research Institute were observed under moderate high temperature to understand the physiological response of lablab bean under heat stress and apply to breeding program. Comprehensive evaluation of three growth indicators, plant height, leaf area and dry weight were conducted. We selected L3 and L19 as heat susceptible accessions, and L12 and L14 as heat tolerant accessions. After 35°C treatment for 1 day, net assimilation rate was induced. At the same time, stomatal conductance and transpiration rate raised, indicating lablab bean could alleviate heat damage by transpiration. Maximal quantum efficiency of PSII photochemistry (Fv/Fm) did not change in heat susceptible accessions. However, Fv/Fm of heat tolerant accessions slightly decreased and non-photochemical quenching coefficient (qN) increased, indicating that PSII could be damaged and excessive energy was dissipated thermally. Under heat stress, L12 and L14 accumulated less malondialdehyde (MDA), suggesting that heat tolerant accessions have less oxidative pressure. Antioxidant enzymes ascorbate peroxidase (APX) and catalase (CAT) were induced after heat treatment. However, peroxidase (POD) activity and proline content remained at the same level. In order to establish an index to screen heat tolerance rapidly, we determined the correlation between semi-lethal temperature and growth parameters, using detached leaves to give heat treatment from 30°C to 60°C. Correlation between chlorophyll fluorescence and growth parameters were low. The correlation between cell membrane thermostability (CMS) and plant height were medium level. In conclusion, MDA content and CMS of detached leaves have higher correlation with heat tolerance, indicating that MDA and CMS can apply to heat tolerance selection in the future.