Response Of Camellia Oleifera Leaves And Root Anatomy To Drought And Nitrogen Addition

In the context of global climate change,drought is becoming more and more frequent, which is an important factor limiting plant growth.Plants can self-regulate to cope with drought,so studying plant responses to drought is very necessary.Nitrogen is an essential nutrient for plant growth,participating in various stages of plant growth and development and playing an important role in plant response to adverse environments.Plant anatomical structure is a key basis for understanding the correlation between physiological and structural functions and directly reflects plant growth and development,which can provide a deeper understanding of plant growth and stress response.Camellia oleifera is an important woody oil tree species with extremely high economic and ecological value.It mainly grows in the southern hilly area,where the soil nutrient is poor,and woodland fertilization is an important management measure.However,how drought and fertilization affect leaf and root anatomy of camellia remains unclear.Therefore,in this study,the 3-year growth forest No.53 camellia saplings were selected as the research object,and the settings were no fertilization under normal irrigation（N₀W）,10 g nitrogen fertilizer under normal irrigation（N₁W）,20 g nitrogen fertilizer under normal irrigation（N₂W）,no fertilization under drought（N₀D）,and 10 g nitrogen fertilizer under drought（N₁D）.Pot control experiment of 6experimental groups under drought application of 20 g nitrogen fertilizer（N₂D）was conducted to study the effects of drought and nitrogen application on root anatomical structure of camellia saplings of different diameter classes and leaf anatomical structure at different periods,and to explore the response of leaf and root anatomical structure of camellia to drought and nitrogen addition,so as to provide theoretical basis for camellia growth under drought environment.The main research results are as follows:（1）Drought significantly affected the plant height,ground diameter,and biomass of leaves and roots of order 1～3 of camellia saplings,while nitrogen application alleviated the effects to some extent.Under drought conditions,nitrogen application increased plant height,ground diameter and biomass,and nitrogen application was beneficial to the growth of camellia saplings.（2）Drought inhibited the growth of leaf epidermis,palisade tissue,spongy tissue and leaf thickness of camellia saplings;The effects of nitrogen fertilization on leaf anatomy were changed.Under drought conditions,nitrogen fertilization could increase the epidermal thickness of camelia leaves,but the effects on palisade tissue and spongy tissue were different.In May,fertilization under drought conditions inhibited the palisade of spongy tissue and promoted the growth of spongy tissue,while palisade tissue thickness increased by 13.7%in August,without significant changes in spongy tissue.（3）Drought significantly inhibited the growth of 1-3rd grade roots,but nitrogen fertilization effectively alleviated the inhibitory effect of drought on the growth of the 1-3rd grade root system.Under drought conditions with nitrogen fertilization,the growth of the primary root diameter,cortex thickness,and central column diameter of Camellia oleifera saplings was promoted,and the application of 10 g nitrogen fertilizer had the greatest effect on the growth of the primary root.Nitrogen fertilization affected the growth of the central column diameter and cortex thickness of the secondary root,which increased with increasing nitrogen fertilization.The central column diameter increased significantly.Under drought conditions,the diameter,cortex thickness,and central column diameter of the third-level root all increased significantly after nitrogen fertilization.The anatomical characteristics of the root system of Camellia oleifera saplings were significantly positively correlated with water and nitrogen levels.In conclusion,drought inhibited the growth of camellia saplings and changed the leaf and root anatomical structure of camellia saplings,while nitrogen application could alleviate the effects of drought.Under drought,nitrogen application effectively promoted the biomass accumulation of camelia leaves and roots.The thickness of leaf epidermis and palisade tissue significantly increased,and the thickness of root cortex and diameter of middle column significantly increased.However,excessive fertilization can also produce certain inhibitory effect.Therefore,it is expected that reasonable fertilization management can alleviate the adverse effects of drought on the growth of camellia saplings,and reasonable fertilization can promote the cultivation of camellia plantation under the background of global climate change.