Effects Of Slow-release Fertilizer On Photosynthetic Physiology,Growth And Quality Of Taxus Chinensis Under Drip Irrigation Conditions

Taxus chinensis is a kind of precious multifunctional tree species,which has many uses such as timber gathering,ornamental and medicinal.Due to the unreasonable development and utilization for a long time,the resources of Taxus chinensis are seriously reduced.Therefore,how to promote the rapid growth of Taxus chinensis trees,in order to protect and enrich its resources,is particularly important.Slow-release fertilizer is a new type of fertilizer that slowly releases nutrients in the soil and provides nutrients for crops in the long term.It can maximize the utilization of fertilizers and effectively reduce their harm to the environment.However,there are few studies on photosynthesis,growth and quality of Taxus chinensis with slow-release fertilizer.Therefore,in this experiment applied Aolu 5 slow-release fertilizer to southern Taxus chinensis from April to October in 2021 and 2022,and set six different slow-release fertilizer application rates,namely CK（0 kg/m³）,F1（1.5 kg/m³）,F2（2 kg/m³）,F3（2.5 kg/m³）,F4（3 kg/m³）,F5（3.5 kg/m³）.Analyze the effects of different dosages of slow-release fertilizer on the growth,physiological characteristics,photosynthesis,and effective components of Taxus chinensis seedlings,in order to select the optimal dosage of slow-release fertilizer for the growth of Taxus chinensis seedlings.The test results indicate that:1.Under suitable water conditions,with the increase of the amount of slow-release fertilizer,the chlorophyll a,b,and total chlorophyll content in the leaves of Taxus chinensis showed a trend of first increasing and then decreasing with the increase of the amount of slow-release fertilizer.In May,July and October,the total amount of chlorophyll a,b and chlorophyll in F2-F4 treatment was significantly increased compared with that in CK treatment.During F3 treatment,the chlorophyll a,b,and total chlorophyll content in the leaves of Taxus chinensis reached their maximum values,followed by F4 and F2 treatments.2.The net photosynthetic rate,stomatal conductance,and transpiration rate of Taxus chinensis leaves showed an increasing and then decreasing trend with the increase of slow-release fertilizer use,while the intercellular CO₂ concentration of the leaves showed an opposite trend.The net photosynthetic rate,stomatal conductance and transpiration rate of leaves treated with F2-F4 were significantly increased compared to CK treatment,but the photosynthetic characteristics began to decrease beyond F3 treatment,which was not conducive to promoting leaf photosynthesis.Due to the high nitrogen content of the soil,it indirectly inhibits the net photosynthetic rate.Under the F3 treatment level,the net photosynthetic rate,stomatal conductance and transpiration rate of leaves reached the highest,while the intercellular CO₂concentration was the lowest.3.Under suitable water conditions,with the increase of slow-release fertilizer dosage,the light energy conversion efficiency Y（Ⅱ）,photochemical quenching coefficient q P and electron transfer rate ETR of each treatment increased with the increase,but began to decline slowly when the application amount exceeded a certain amount.Fv/Fm of F2-F5 treatment in July was significantly higher than that of blank control CK treatment,but there was no significant difference among treatments in May and October.Compared with CK treatment,the light energy conversion efficiency Y（Ⅱ）,photochemical quenching coefficient q P and electron transfer rate ETR of F3 treatment increased significantly and reached the maximum.In the middle of May,July and September,the NPQ of leaves treated with F3 decreased significantly and reached the lowest level compared with that treated with CK.The application of moderate slow-release fertilizer alleviated the nutrient deficiency of Taxus chinensis promoted the absorption of light energy by leaves,and alleviated photoinhibition.4.Under suitable water conditions,with the increase of slow-release fertilizer dosage,the content of malondialdehyde and relative conductivity of each treatment showed a trend of first decreasing and then increasing,while the content of soluble protein showed an opposite trend.The soluble protein content in the leaves of F2-F4 treatment was significantly higher than that of CK treatment,while the soluble protein content in the leaves of F3 treatment was the highest.The content of malondialdehyde and relative conductivity of leaves treated with F3 significantly decreased to the lowest level.The amount of slow-release fertilizer used during F3 treatment is beneficial for increasing the soluble protein content of Taxus chinensis leaves,while reducing the relative conductivity and malondialdehyde content of the leaves.5.Under suitable water conditions,with the increase of slow-release fertilizer dosage,the increase in plant height,stem,crown width,and LAI of each treatment also increases.When the dosage exceeds a certain level,it is not conducive to growth.In two years,the increase of plant height,crown width and LAI in F2-F4 treatment was significantly increased compared with CK treatment.There was no significant difference in the increment of ground stem of each treatment in 2021,and the increment of ground stem of F3 treatment in 2022 was significantly higher than that of other treatments.The content of flavonoids and polysaccharides in leaves treated with F2-F4 significantly increased compared to CK treatment.The content of flavonoids and polysaccharides in the leaves of each treatment in August was lower than that in November.In the past two years,the plant height,rhizome,crown width,LAI increase,and flavonoid and polysaccharide content of Taxus chinensis seedlings reached their highest levels under F3 treatment.