The Effect of Plant Growth Regulators on Chinese kale (Brassica oleracea L. var. alboglabra) to Waterlogging stress
Date Issued
2011
Date
2011
Author(s)
Shin, Wan-Jyun
Abstract
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.
Subjects
Chinese kale
hypoxia stress
plant growth regulators
seaweed extracts
chlorophyll fluorescence (Fv/Fm)
stress tolerance
Type
thesis
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