| Tumorous stem mustard(Brassica juncea var.tumida Tsen et Lee)commonly known as pickle,is a stem variety mustard species of Brassica in the cruciferous family,with an enlarged tumorous stem as the main product organ.In the production,the tumorous stem mustard often appears these phenomenon such as axillary bud extraction and early bolting due to the unfavorable environment,especially in the introduction cultivation of open fields in northern area,the light and temperature inhibit the incidence of tumorous stem occurrence.Therefore,this experiment studied the effects of short days,the interaction between short days and sowing dates,and different daily temperature on the growth and development of tumorous stem mustard to clarify the appropriate light and temperature for the growth and the occurrence of tumorous stem,exploring the physiological mechanism of of tumorous stem occurring,which canprovide theoretical reference for the introduction and cultivation of tumorous stem mustard in northern China.The main research results are as follows:(1)Using a medium mature tumorous stem mustard variety “Legend of Yongan” as the test material and natural light as control,the effects of short day treatments at 6 h and 8 h with the time duration 10 d,20 d and 30 d on the growth and tumorous stem occurring of tumorous stem mustard in northern greenhouse were studied.The results showed that the tumorous stem was formed by the continuous division of myeloid cells.Short day treatment could advance the occurrence of tumorous stem,and compared with the control,short day treatment at 6 h/d and 8 h/d could advance 5 d at the occurrence of tumorous stem and the rapid swelling stage of tumorous stem,respectively.The shorting day treatment inhibited the growth of tumorous stem mustard,plant height,development degree,leaf length and leaf width significantly,increasing the activities of antioxidant enzymes(SOD,POD and CAT)during treatment obviously.Short day treatments decreased the stem weight per plant,increasing stem type index,reducing the contents of soluble sugar and soluble protein in tumorous stem,while elevating glucosinolate content along withcrude fiber content decreased in some treatments.Linear regression analysis and correlation analysis showed that stem diameter was positively correlated with cumulative sunshine duration and negatively correlated with average daily sunshine duration.The critical daily sunshine duration of“Legend of Yongan” was 11.17 h and 10.93 h for tumorous stem occurring and tumorous stem rapid expansion under natural light conditions in the northern greenhouse.The incidence of tumorous stem occurring was positively correlated with plant height,development degree,leaf length,leaf width,the contents of soluble sugar and soluble protein,and negatively correlated with the activities of SOD,POD and CAT.The comprehensive evaluation results showed that short day treatment could advance the tumorous stem occurring and expanding rapidly,but was not conducive to the growth,yield and quality of tumorous stem mustard.(2)Using “Jiaoyan No.1” which is theearly mature tumorous stem mustard variety as the test material,the effects of different sowing date(August 2nd,August 7th,August 12th)and short day treatment time of 6 h/18 h(0 d,5 d,10 d)on the occurrence of tumorous stem,growth and development in tumorous stem mustard of northern open field were studied.The results showed that delayed sowing date and increased short day treatment time delayed plant growth,and plant height,development degree,leaf length and leaf width decreased significantly along withantioxidant enzyme activity elevating.Meanwhile,bolting rate decreased,stem diameter increasing.Among them,the plants did not have bolting and tumorous stem occurring by treating with short day treatment 10 d when the sowing date was August 12 th.There existed correlations between tumorous stem mustard bolting and growth,carbon and nitrogen metabolism and endogenous hormone content,which was positively correlated with plant height,spread degree,leaf length,leaf width,the contents of soluble protein and gibberellin,negatively correlated with soluble sugar content and superoxide dismutase activity.(3)Using “Jiaoyan No.1” which was the early mature tumorous stem mustard variety as the test material,the effects of different daily average temperatures(24℃/20℃,20℃/16℃,16℃/12℃)on the growth and development of tumorous stem mustard were studied,with room temperature as control.The results demonstrated that with the decrease of average daily temperature,plant height,development degree and leaf width decreased,stem diameter and leaf length increasing,SOD and POD activities elevating.At the same time,the bolting time delayed,the bolting rate reducing.And no bolting occurred when the average temperature of the day was lower than 14℃.Low temperature affected carbon and nitrogen metabolism and endogenous hormone content of tumorous stem mustard.The contents of soluble sugar and soluble protein decreased gradually with daily temperature decreasing,while auxin content decreased at the early stage and increased at the later stage,and gibberellin and ababolic acid contents decreased.There existed a significant positive correlation between bolting rate and plant growth,the contents of soluble protein and gibberellin,catalase activity.In conclusion,in the treatment range of this experiment,short day treatment with 6 h/d and 8h/d could promote the early occurrence of tumorous stem,while it was not conducive to the growth,yield and quality of tumorous stem mustard.Delaying sowing date and shorting day treatment could delay bolting and promote the occurrence of tumorous stem.It could effectively inhibit bolting and increase stem diameter with the cumulative average daily temperature lower than 20℃. |
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