| Rapeseed is one of the most important oil crops in the world, the yield and planting area of rape inChina occupied the first place in the world.85%of the total area of rapeseed in China distributes in theReaches of Yangtze River, which has rich water resources and higher underground water, most rapeseedgrows after rice, in this rotation system, the paddy soil and rich rain could easily lead to waterloggingand reduction of the yield and quality of rapeseed. At present improved agronomic measures andwaterlogging-tolerant varieties optimization were applied to relief the damage of waterlogging. Becauseagronomic measures based on furrowing consumes material and workforce, and the breeding cycle islong and seriously regional restricted, it is hard to achieve satisfactory waterlogging control effects.Therefore, it is vital to reveal the waterlogging-tolerant mechanism of rapeseed and explore economicand effective waterlogging control measures that are easy to spread.Zhongshuang No.9and Zhongyouza No.12were used as experimental materials to carry out thepot experiment aimed at systematically studying the influence of sustainable waterlogging on thegrowth and physiological metabolism of this two rape species, comparing and analyzing the differencesof shoot and root response to waterlogging, preliminarily determining the death time of this two rapespecies;6-benzyl aminopurine (6-BA), abscisic acid (ABA), salicylic acid (SA) and uniconazole wereused to select the optima one that could alleviate the damage from waterlogging and then tried toinvestigate relative mechanism of waterlogging alleviation. The results as follows:1. It showed that continuous waterlogging stress seriously affected the shoot and root ofZhongshuang No.9and Zhongyouza No.12. Overall, the growth of rape was slightly promoted in thebeginning of waterlogging and then suppressed. In the later period of waterlogging, the growth anddevelopment of rape were significantly inhibited, and the damage of waterlogging got strengthened withwaterlogging stress prolonging: the rate of superoxide radical (O2-) production and the MDA contentwere significantly increased, total chlorophyll concentration and antioxidant enzyme activity (SOD andCAT) decreased seriously, roots get decayed accompanied by the decrease of biomass and morphologyparameters (root length, root surface area and root volume). After waterlogging23-25days, almost allof the rapeseed seedings died.The total effects' trends of waterlogging stress on rape shoot and root were similar, while the timewhen the growth and physiological metabolism of root changed significantly was earlier than that ofrape shoot. After waterlogging for5days, some physiological indexes of root changed obviously, butthe time when some indexes of rape shoot changed significantly was10days after waterlogging started.It was concluded that root of rape could perceive waterlogging stress and reacted earlier than shoot did.We primarily identified waterlogging5d as the critical point of waerlogging tolerance of these tworapeseed varieties.2.6-BA, ABA, SA and uniconazol were foliar sprayed after waterlogging for5days, resultsindicated that application of plant growth regulators could alleviate waterlogging damage in certain extent. Among these plant growth regulators6-BA and ABA had better and permanent effect.Chlorophyll content, shoot and root dry weight, plant height and root length were increased by6-BAand ABA treatment, while soluble sugar content and MDA content were reduced. The death time ofwaterlogged rapeseed was delayed about3to5days by6-BA and ABA treatment.3. Zhongshuang No.9and Zhongyouza No.12were sprayed with6-BA to study the influencemechanism of6-BA on the waterlogged rapeseed after waterlogging. Results showed that waterlogginghad aftereffect on the growth and development of rape. Even when waterlogging stress was eliminated,rapeseed could not recover in short time.6-BA promoted the resistance and growth recovery ofwaterlogged rape by increasing total chlorophyll content, carotenoid content, SOD and CAT activity.However, the rate of O2-production and H2O2content and the MDA content were significantly reduced.It was thus concluded that waterlogging led to the increase of oxygen free radical, and6-BA enhancedwaterlogging tolerance of rape through improving antioxidant enzymes activities and thus scavengedoxygen free radical weakening lipid peroxidation of membrane, and simultaneously inhibitedchloroplasts destroyment caused by H2O2. Therefore, rape could keep certain chlorophyll andcarotenoid content in order to grow better and recover during and after waterlogging stress. |
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