Experimental Study On Lignification Process And Nitrogen Regulation Of Camellia Oleifera Spring Shoot

Camellia oleifera is one of the four woody oil crops in the world and an important economic tree species in south China.The main propagation mode of Camellia oleifera is seedling anvil grafting method,the quality of scion will affect the growth of grafted seedlings.It was found that the scion with different lignification degree of Camellia oleifera had significant effect on the growth of grafted seedlings,and lignin was an important factor affecting the quality of grafted seedlings.Therefore,in this study,the improved ’huajin’ three-year-old tree was used as the research material,and the single factor control test was adopted to set blank control and five nitrogen concentration gradients 50 mg·L-1、100 mg·L-1、150 mg·L-1、200 mg·L-1、250mg·L-1(N1、N2、N3、N4、N5).To study the growth,nutrient content,morphological and anatomical differences and lignin synthesis differences of spring shoot under different nitrogen levels,and to explore the effects of different nitrogen levels on the growth and lignification of spring shoot.In order to provide reference for further scientific management of cutting orchard and improving the quality of Camellia oleifera scion.The main results are as follows:(1)The morphological changes and nutrient contents of spring shoots under different nitrogen levels were studied.The results showed that:There were significant differences in the length,diameter and section spacing of spring shoots under different nitrogen levels.The length,diameter and section spacing of spring shoots under N3,N4 and high nitrogen(N5)levels were significantly larger than those of other treatment groups,but there was no significant difference in morphological indexes between high nitrogen(N5)levels and N3、N4 levels.During the whole experiment period,the contents of N,P and K in spring shoot showed a decreasing trend,while the C/N ratio showed an increasing trend.The mineral element contents of spring shoot of Camellia oleifera under different nitrogen levels were significantly different,and the contents of N,P and K of spring shoot under N3 level were significantly higher than those of blank control.(2)The paraffin slice of spring shoot under different nitrogen levels was studied.The results showed that the stem structure of spring shoot of Camellia oleifera from inside to outside were pith,xylem,phloem,cortex,periderm and epiderm.At 9d after treatment,the xylem percentage and phloem percentage of spring shoot were about 11%.From 18d to 36d after treatment,the xylem percentage of spring shoot under different nitrogen levels was significantly different,the xylem percentage value of spring shoot under N4 and high nitrogen(N5)levels was significantly lower than that under blank control and low nitrogen(N1)levels.At 45d after treatment,the xylem percentage increased slightly under different nitrogen levels.Overall,with the increase of nitrogen level,the spring shoot’s xylem percentage decreased,while the phloem percentage increased.(3)The regulation of lignin synthesis under different nitrogen levels was studied.The results showed that the relative content of G-lignin under different nitrogen levels increased firstly after declining,and the relative contents of S-lignin and H-lignin decreased gradually.From the whole,the contents of G-lignin and S-lignin in spring shoots of Camellia oleifera were higher,while the contents of H-lignin were lower.During the whole experiment period,the lignin content under different nitrogen levels was significantly different,the lignin content under high nitrogen(N5)level was significantly lower than that under low nitrogen(N1)level.And the cellulose content under different nitrogen levels was significantly different,the cellulose content under N4 and high nitrogen(N5)levels was significantly higher than that under blank control and low nitrogen(N1)levels.The results showed that with the growth of spring shoot,lignin content increased while cellulose content decreased.During the whole experiment period,the activities of lignin-related enzymes PAL and 4CL increased,while the activities of CCR and POD increased firstly after declining.Variance analysis showed that the PAL,4CL,CCR and POD enzyme activities in spring shoot were significantly different under different nitrogen levels,and the PAL,4CL,CCR and POD enzyme activities were higher under blank control and low nitrogen level(N1).(4)According to the comprehensive evaluation results of principal component analysis,the morphological growth,nutrient element content and lignification degree of spring shoots at N4 level were the highest,followed by high nitrogen(N5),N3,N2,low nitrogen(N1)and blank control.Therefore,we suggested to spray 200 mg·L-1 nitrogen to improve the quality of spring shoots of Camellia oleifera.