| Horsfieldia hainanensis Merr.has high medicinal value,material economic value,but also high-quality green tree species,but almost in danger.It is of great significance to strengthen the study on the cultivation and management of Horsfieldia hainanensis Merr.,to provide theoretical basis for its seedling raising and high quality seedlings for afforestation projects.In the process of plant growth,the supply level of light and nitrogen balance is the basis for the best interaction effect,and plays a key role in improving plant photosynthesis.In the past,the research on Horsfieldia hainanensis Merr.mainly focused on the phenology,seed propagation and renewal methods,medicinal value and so on,while there was little literature on the effects of two factors on the growth and physiological effects of seedlings.In this experiment,seedlings of Horsfieldia hainanensis Merr.were used as test materials.Four kinds of light(100%,67.5%,45.7%,15.6%of natural light)and five kinds of nitrogen(0,1.8,3.6,5.4,7.2g pure N per plant)two-factor completely randomized block scheme was adopted to determine the optimum conditions of light and nitrogen for the growth of Aegiceras corniculatum seedlings by measuring growth,photosynthesis,physiological and nutrient contents and other indicators.The results show:(1)compared with the control group,67.5%and 45.7%natural light transmittance significantly increased plant relative growth of height and stem,leaf area,the root system,the biomass dry weight and root-shoot ratio,but 15.6%natural light inhibited seedling growth.Under the same shade,the growth index of seedlings increased first and then decreased with the increase of nitrogen.The seedlings grew fastest from June to September,with the plant height accounting for 79.3%of the whole period and the stems and stems accounting for 66.7%of the total.On the whole,the combination of 1.8 g per plant low nitrogen treatment and 67.5%light transmittance treatment is good for seedling growth.It is better to carry out 45.7%light transmittance after nitrogen content is higher than 3.6g per plant.(2)Under the same nitrogen,shading significantly decreased the soluble sugar content of medium(SS),soluble protein(SP),free proline(Pro)and malondialdehyde(MDA),that shading helps alleviate the light stress of seedlings in full sunlight.Shading significantly increased the final SP,POD and SOD activity,reflecting the antioxidant enzyme activity was raised to remove reactive oxygen species,to maintain normal growth.Application of nitrogen fertilizer helps to reduce the accumulation of antioxidant enzymes caused by excessive light intensity in the middle period.At the final stage,SS,Pro,and POD were increased first and then decreased after application of nitrogen fertilizer,and the 45.7%light transmittance of MDA was significantly reduced.(3)Shading significantly increased chlorophyll content and net photosynthetic rate(Pn)of seedlings under the same nitrogen level.With the increase of shading,Pn of two periods,middling stomatal conductance(Gs)and transpiration rate(Tr)increased at first and then decreased,and the crest was at 67.5%light transmittance,indicating that moderate shade could improve photosynthetic efficiency.However,nitrogen content of 0,7.2g per plant with the light transmittance of 15.6%significantly increased the initial fluorescence(Fo),reduced the actual quantum yield Y(II),electron transfer rate(ETR)and photochemical quenching coefficient(qP),indicating that excessive shading in the absence and excess of nitrogen can reduce the light energy of the photochemical process.Compared with no nitrogen and 7.2 g per plant nitrogen fertilizer,the treatment with 1.8,3.6,and 5.4 g nitrogen per plant significantly increased the Fo,Y(II),ETR,reduced the quantum yield Y(NPQ)and non photochemical quenching coefficient(NPQ).(4)Under the same nitrogen conditions,shading reduced the content of ammonium nitrogen in soil and leaves of mid-season seedlings,and the soil urease activity and leaf glutamine synthetase decreased significantly.Under the same shade,the application of nitrogen fertilizer can increase the total nitrogen of soil and leaves,soil ammonium nitrogen in mid-season,total nitrogen of leaves and ammonium nitrogen of soil in the final stage,but decreased at the end of the season.Under the condition of high nitrogen(N?3.6g/plant),45.7%transmittance treatment was beneficial to increase the content of total nitrogen in soil and leaves in mid-season,but decreased when the light transmittance was only 15.6%.When N ? 5.4g/plant,shading favored the final leaf total nitrogen content,but shading instead reduced the total nitrogen content of the final leaf when nitrogen content was 7.2g/plant.(5)The highest degree of membership and seedling quality of Horsfieldia hainanensis Merr.was treated with L1N2(L=67.5%,N=3.6g/strain),which was a medium-resistance type.For the same light level,the degree of membership and QI applied to nitrogen fertilizer treatment were greater than those without nitrogen treatment.The overall growth quadratic response surface is positive convex,and the maximum light-nitrogen coupling level is near L=0.65,N=4.6g.In summary,under the effect of moderate shading and nitrogen application,On the one hand,Horsfieldia hainanensis Merr.seedlings can alleviate the light stress by regulating the physiological osmotic adjustment of seedlings and antioxidant enzymes,and on the other hand,enhance photosynthetic efficiency and nitrogen content in the soil and leaves,promoting the growth and development of seedlings.Whether full or over shade,nitrogen deficiency or excess are not conducive to seedling growth.In the process of cultivation of Horsfieldia hainanensis Merr.seedlings,it is most beneficial to the growth of seedlings to create 67.5%light and apply nitrogen fertilizer to about 4.6g. |
PDF Full Text Request