植物生長調節物質處理對芥藍淹水反應之影響

Abstract

臺灣夏季高溫多濕且常遭受颱風豪雨的侵襲，蔬菜因淹水逆境造成傷害，無法恢復生長或死亡。近年有多種生長調節物質應用於增強植物對非生物性逆境的抗性。本研究針對夏季芥藍(Brassica oleracea L. var. alboglabra)生產面對淹水傷害之風險，探討施用植物生長調節物質對芥藍在苗期和成株期淹水後之生理影響，以及植物生長調節物質對減輕芥藍淹水傷害的應用效果。芥藍苗期淹水及施用植物生長調節物質的試驗在臺灣大學人工氣候室進行，以‘翠寶’、‘西螺芥藍’、‘白花芥藍’和‘翠津’四個包括一般葉用、苔用的品種供試。各品種先於常溫(25/20℃)下生長四週，在淹水前三天以不同植物生長調節物質處理，再分別於兩種溫度(25/20℃和35/30℃)下淹水三天、排水三天為恢復期。所用植物生長調節物質有海藻萃取物(綠寶)、生長素(根毛王)、細胞分裂素(速喜)、硫酸鋅及腐胺。結果在兩個溫度下受到淹水的逆境影響以在25/20℃比在35/30℃小，而各品種對高溫或淹水之耐受性以‘西螺芥藍’最差，‘翠寶’較佳。在常溫下淹水處理前施用生長調節物質，以施用海藻萃取物(綠寶)對於芥藍各品種淹水生理反應之緩和效果最好，增加葉片相對含水量及葉片相對葉綠素含量、減少電解質滲漏率及丙二醛含量、葉綠素螢光反應Fv/Fm的差值減少以及脯胺酸含量增加。但在排水恢復期這些生理指標的恢復效果比其它調節物質硫酸鋅、腐胺、生長素(根毛王)小。在高溫下芥藍淹水前，生長調節物質處理對減輕芥藍生理指標變化幅度的效果顯示，施用海藻萃取物減輕淹水後的葉片生理指標變化、施用硫酸鋅減輕淹水後及恢復期的生理指標變化。芥藍成株夏季淹水試驗增加供試品種數到8個，在農業試驗所試驗田(台中霧峰) 分兩批(八月及九月)進行。兩批皆先以穴盤育苗，待植株長至3-4片本葉，定植於試驗田，移植前所有植株施用生長素(根毛王) 0.5 mg/L。定植後約5週、即採收前進行淹水處理。在淹水處理前三天先給予不同的植物生長調節劑，有生長素(根毛王，0.5 mg/L)、海藻萃取液(綠寶，稀釋800倍；天下補，稀釋800倍)、細胞分裂素(速喜，稀釋600倍)、硫酸鋅 (稀釋2000倍)及腐胺 (2 mM)共六種。試驗處理分為不淹水(對照組)、不淹水但施用植物生長調節劑、淹水前施用不同植物生長調節劑以及淹水而未施植物生長調節劑四種。田間進行淹水三天、再排水五天，芥藍植株大量萎凋或死亡，處理生長調節劑之植株黃化萎凋情形較緩和。各品種對淹水逆境之反應表現差異，各項生理指標變化由大至小的品種在八月試驗依序為翠津、黃花芥藍、芥藍花、翠寶，而在九月依序為西螺芥藍、白格林、格林花、蕙津、翠寶。綜合八、九月田間施用各植物生長調節物質的效果，以綠寶、天下補(皆為海藻萃取物)和速喜(細胞分裂素)對於減輕芥藍淹水後、排水恢復期生理反應的效果較好。植株因淹水逆境造成的鮮、乾重損失以‘白格林’最嚴重，而受淹水影響仍可採收者為‘翠寶’。各植物生長調節物質前處理對各品種皆有不同程度的減緩失重。整體上，海藻萃取物—天下補、綠寶和細胞分裂素(速喜)可減少芥藍因淹水逆境所造成的失重。藉由非破壞性且快速的葉片葉綠素螢光反應(Fv/Fm)分析，可觀察各芥藍品種在淹水前、後的光合作用能力變化。淹水前各品種的Fv/Fm值介於0.8~0.6，經過淹水三天後，各品種之Fv/Fm值下降，但程度不同。到排水恢復期F1品種如 ‘翠寶’Fv/Fm值稍有回復，而較不耐淹水的品種如‘黃花芥藍’和‘白花芥藍’的Fv/Fm值則持續下降，可作為芥藍在淹水逆境下的生理指標。根據研究結果，夏季栽培芥藍，在品種的選擇上可選用葉用F1品種如‘翠寶’，遇夏季豪雨造成的影響傷害較小。而苔用品種會因溫度不適，生長勢不佳，加上淹水逆境的影響，傷害更大。芥藍在不同生長時期所經歷淹水逆境的表現不同，在苗期較成株對於淹水忍受度較大。在栽培期適時施用植物生長調節物質能減緩其淹水傷害，若如其他研究增加施用植物生長調節物質的次數，可能效果更好。

The summer in Taiwan is high in temperature and humid, and it is common that vegetable crops succumb to heavy rain and typhoons. Plants are not able to restore their growth and crop loss results. Recently there are several plant growth regulators (PGRs) in market for use to diminish the crop loss from abiotic stresses. The study is undertaken to investigate the physiology responses of Chinese kale (Brassica oleracea L. var. alboglabra) upon flooding in summer, both at seedling and ready-to-harvest stages and to evaluate the efficacy of various plant growth regulators to sustain plants from the stress. The seedlings of four Chinese kales varieties ( cv. ‘Tsuei-Bao’(F1), ‘Si-lo’, ‘White-flowered’ and ‘Tsuei-jin’ (F1)) were grown under 25/20℃(day/night) for four weeks before 3 days of flooding at room temperature (25/20℃) or at high temperature (35/30℃). Three days prior to flooding plants were given different PGRs and flooding was lasted for three days, then followed by 3 days of drainage for plant recovery. The study was carried out at the phytotron of National Taiwan University, Taipei and the PGRs including auixn (Lysine#3), seaweed extract (Algreen), cytokinin (Biogrow), ZnSO4 and putricene were tested. The flooding impact under 25/20℃was milder than 35/30℃ and there are varietal differences in their response to flooding and/or high temperature with ‘Tsuei-Bao’ (F1) being most tolerant and ‘Si-lo’ the least. Pretreatment of seaweed extract (Algreen) gives better ameliorative effect to Chinese kale plant flooded under 25/20℃(D/N) in terms of keeping higher relative water content (RWC) and relative chlorophyll content (SPAD value), less electrolyte leakage rate and malon- dialdehyde (MDA) content, less drop in chlorophyll fluorescence (Fv/Fm) and higher content of proline. However, the mitigating effect from seaweed extract application to the plants during recovery period was less than from Lysine#3, zinc sulfate and putrescine. The pretreatment of seaweed extract to Chinese kale plants before being flooded under 35/30℃ resulted in less change of various plant physiological indices in response to flooding and the pretreatment of ZnSO4 gave the plants less physiological response during both flooding and recovery time. Field experiments with eight varieties in total including both leaf type and fleshy flower stalk type were conducted in August and September at experimental farm of Taiwan Agricultural Research Institute in Wu-Feng, Taichung. Plug seedlings of three to four leaf stage were treated with 0.5 mg/L Lysine#3 (auixn) before field transplanting. About 5 weeks after transplanting, plants at ready to harvest stage were waterlogged. Three days prior to flooding, the plants were given one of six PGRs including auxins (Lysine#3, 0.5 mg/L), seaweed extracts (Algreen, dilution factor(DF) 800；Keltak, DF 800), cytokinin (Biogrow, DF 600), ZnSO4 (DF 600) and putrescine (2 mM). Field treatments included no waterlogging (control), PGRs pretreatment without waterlogging, PGRs pretreatment with waterlogging, and waterlogging only, three replicates for each treatment. Flooding lasted for three days, followed by draining the field for five days for plant recovery. The plants without PGR pretreatment wilted or died after waterlogging, and treated plants had less yellowing or wilting. The intensity of the varietal response to field flooding is determined from the change of various physiological indices. The response intensity from 4 varieties to August flooding in descending order follows ‘Tsuei-Jin’ (F1), ‘Yellow-flowered’, ‘Kai-lan Flower’, and ‘Tsuei- Bao’ (F1). The response intensity from 5 varieties in September in descending order gives ‘Si-lo’, ‘White-gelin’, ‘Ge-lin Flower’, ‘Huei-Jin’ (F1) and ‘Tsuei-Bao’ (F1). The comprehensive results from both August and September study showed that both seaweed extracts (Algreen and Keltak) and cytokinins (Biogrow) had better alleviating effects than other PGRs tested to plants in flooding and in recovery. The plant dry weight and fresh weight loss from waterlogging stress was most severe in ‘White-gelin’ while ‘Tsuei-Bao’ (F1) remained most for harvest. Overall seaweed extract (Keltak) pretreatment could most reduce the plant weight loss from waterlogging and followed by seaweed extract (Algreen) and cytokinins (Biogrow). The chlorophyll fluorescence (Fv/Fm) being a fast and non destructive index indicates the photosynthetic rate of plants upon flooding. The Fv/Fm value decreased from regular 0.8-0.6 upon flooding at high temperature, the value continued to decrease during the recovery period with susceptible plants like ‘White-flowered’ and ‘Yellow-flowered’. While the value would somewhat recover after drainage in resistant plants like ‘Tsuei-Bao’ (F1). The results suggest that ‘Tsuei-Bao’ (F1) is a good choice for summer planting for its less damage from flooding and the fleshy flower stalk type is not suitable for early fall-winter season when temperature still remains high. Chinese kale at seedling stage has better tolerance to flooding than plants of ready-to-harvest stage. The application of PGR is helpful to reduce the crop loss of Chinese kale from flooding. More times of PGR application as suggested in other study may also enhance the protective effect.