| Celery(Apium graveolens L.)is a annually and biennially herbaceous vegetable of umbelliferae and is an important vegetable of leafy vegetables.In celery cultivation,the seed of celery is fruit with leather surface and volatile oil inside,which leads to poor water permeability and slow germination rate and poor uniformity.At the same time,as a coldresistant vegetable,celery requires relatively cold and humid environmental conditions,so it does not grow well under high temperature and drought conditions.Light intensity plays an important role in seedling growth,morphological formation and metabolism.Excessive or insufficient light intensity will cause stress on seedling growth.The growth density of the seedlings was closely related to the size of the plug.Excessive plug size led to excessive growth density of the seedlings,which was not conducive to obtaining light energy for photosynthesis,and the growth of the seedlings was inhibited.Low rate and irregular of Seeds germination,inappropriate temperature,light intensity conditions and plug specifications all had effects on the large-scale production and annual production of celery.In order to solve the above problems,this paper carried out research from the two aspects of seed germination and seedling cultivation,in order to improve the speed and uniformity of celery seed germination,and obtain the cultivation method of high-quality seedlings.In this study,’Shenqin 2’ was used as the material and the split zone test design method was adopted.Three reagents were combined(5 g/L NaOH+10%PEG,10%PEG+500 mg/L chitosan,5 g/L NaOH+500 mg/L chitosan)as the main factor and temperature(18℃,24℃,30℃)as the secondary factor to explore the influence of chemical reagents and temperature on seed germination speed and uniformity.The celery seedlings cultured for 60 days were used as the test material to compare the effects of different temperature(23℃,30℃)on quality,oxidation resistance and growth of celery seedlings,and determined the appropriate temperature for celery seedling.At the same time,used the plug cultivation method,Different specifications of the plug(72-hole,128-hole,288-hole)as the main factor,and the light intensity(25.84 μmol m-2·s-1,74.12μmol·m-2·s-1,137.03 μmol m-2·s-1,165.19μmol·m-2·s1)was used as a secondary factor to cultivate celery seedlings,used the split zone test design method to study the effects of plug size and light intensity on growth index,quality and antioxidant of celery seedlings,and to obtain the cultivation methods and techniques of highquality seedlings.The main results are as follows:1.The three chemical reagents had no effect on germination rate of celery seeds,but had significant effect on germination potential and germination index.Under the same temperature,Pro content was not different,the activities of SOD and CAT were significantly reduced and the germination potential and index were significantly increased after the chemical reagent treatment,MDA content was significantly decreased under the conditions of T1(NaOH+PEG)and T3(NaOH+chitosan).Under the same reagent treatment,with the increase of temperature,the content of MDA and Pro in seed were decreased,the activities of SOD and CAT were decreased first and then increased,germination potential and index were increased significantly.The above results showed that the germination potential and germination index of seeds had the best performance under the same reagent treatment at 30℃.By measuring the hormone content changes of different chemical reagents in the process of seed germination at 30℃,the hormone changes in the process of seed germination and the effect of chemical reagents treatment on the hormone content in seeds were explored.The results showed that from the first day to the fifth day of germination,the content of ABA was significantly decreased,the content of ZA and GA3 were significantly increased.The contents of ABA,ZA and GA3 in seeds were significantly higher than CK(control)under different chemical reagent treatment.There was an interaction between chemical agent and temperature,which significantly affected the germination of seeds.There was no difference in germination potential and germination index between T1B3(NaOH+PEG,30℃)and T2B3(PEG+chitosan,30℃),but they were significantly higher than other treatments.The germination rate of seed under T2B3 was higher than that under T1B3.The results indicated that T2(PEG+chitosan)reagent was beneficial to accelerate seed germination and improve seed germination uniformity under the condition of 30℃.2.Compared with 23℃,the fresh weight,dry weight,plant height,seedling index and stem diameter of the seedling were significantly decreased at 30℃.The content of total phenol,anthocyanin and flavonoids decreased significantly at 30℃.The content of soluble protein and soluble sugar decreased at 30℃.Superoxide anion production rate,the activities of CAT and POD were increased,SOD activity decreased at 30℃.The content of chlorophyll was significantly decreased at 30℃.Therefore,the high temperature of 30℃ inhibits the growth of celery seedlings,decreases the photosynthetic capacity and quality of the seedlings,so it is not suitable for the cultivation of celery seedlings.In comparison,23℃ is more conducive to the growth of celery seedlings.3.The quality and growth of celery seedlings were significantly affected by different plug size and light intensity.Under the same light intensity condition,when the plug size is 72-hole,the stalk diameter,total fresh weight,total dry weight,underground fresh dry weight,seedling index,chlorophyll a,chlorophyll b and carotenoid content of the celery seedlings were significantly higher than those of other plug size.The plant height and soluble sugar content were significantly higher than 288-hole,but the difference was not significant with 128-hole,the content of soluble protein,total phenols and flavonoids were decreased than those of other plug size.Under the same plug size condition,with the increase of light intensity,the plant height,petiole thickness,chlorophyll a,chlorophyll b and carotenoid content of seedling showed a negative correlation trend,the total dry weight,underground dry weight,seedling strength index,soluble sugar,total phenols,anthocyanin and flavonoids of the seedlings under the condition of K3 were significantly higher than other light intensity conditions,and the content of soluble protein under the condition of K3(137.03 μmol·m-2·s1)was significantly lower than other light intensity conditions.The total fresh weight of the seedlings and underground fresh weight were significantly increased under the condition of K4(165.19 μmol·m-2·s-1).The interaction between plug size and light intensity also significantly affected the growth and quality of the seedlings,and the dry weight and seedling strength index of the seedlings were significantly higher than that of the other treatments under 72-plug K3(137.03 μmol·m-2·s-1).It was indicated that the conditions suitable for the efficient growth of celery seedlings within the scope of this experiment was the plug of 72hole and the light intensity of K3(137.03 μmol·m-2·s-1). |
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