Effects Of Waterlogging On Physiological Characteristics And Fruit Quality Of Citrus

Citrus is mainly cultivated in the subtropical monsoon climate area with long rainy season and heavy rainfall in southern China.Due to continuous rain,it is easy to cause different degrees of Citrus waterlogging stress.The phenomenon of accumulated water and soaking root in rainy season and even waterlogging and waterlogging are often seen.Waterlogging stress not only affects the growth and development of citrus,but also has a great impact on fruit setting,yield,fruit and quality,and flower bud differentiation of citrus.In the late spring,early summer and summer,this study simulated the waterlogging stress in the field,explored the critical days of the impact of waterlogging on citrus,monitored the quality changes of citrus fruits after seasonal waterlogging,and analyzed the physiological mechanism of Citrus responding to submergence stress.It lays a theoretical foundation for regulating citrus fruit quality in industry.The main research results are as follows:1.Citrus grown in natural conditions under field conditions,the fruit size was smaller than that of the CK(non waterlogged)citrus(fruit)in the same area,followed by fruit development.The fruit size of CK and waterlogged orchards(WL)did not change significantly.Fruit enlargement and waterlogging stress will reduce the total soluble solid(TSS)and total acid(TA)content of mature fruits,and deteriorate the quality of citrus fruit.2.In the late spring and early summer,the nine-year-old citrus rootstock "citrus" Wenzhou Citrus under the waterlogging stress of 5 d,the citrus leaves had no obvious change in appearance of the roots and leaves.10 d of the waterlogged trees showed obvious symptoms,and the veins of leaves obviously browned,while the veins remained green,and the roots rotted and smelly.With the prolongation of waterlogging time,the symptoms aggravated or even withered and died(20 d).The root system of Citrus roots was earlier than that of leaves.The degree of root injury was closely related to the changes of soluble protein(SP),soluble sugar(SS)content and superoxide dismutase(SOD)activity.Waterlogging stress for more than 10 days at the turn of spring and summer can induce obvious symptoms in leaves and roots,inhibit citrus growth and even dry up and death.At the spring and summer,5 d partial branches of citrus trees were withered,and the lesser damaged citrus trees still had the fruit bearing ability.The fruit setting rate was lower than CK,and the total acid content of mature fruit was higher than CK.3.One-year-old and three-year-old citrus rootstock,leaves yellowing and photosynthetic rate decreased after summer waterlogging stress,and dry and fallen leaves appeared with the extension of waterlogging time.Waterlogging stress affected citrus growth and development,and the ability of young citrus trees to withstand high temperature and waterlogging was 4?6 d.Further continuous waterlogging stress resulted in yellowing and abscission of leaves,decreased net photosynthetic rate,increased contents of stress resistant substances,decreased phloem necrosis and loss of nutrient uptake in roots,and SOD activity and malondialdehyde(MDA)content in plant leaves are closely related to citrus flooding stress.4.Under the condition of photoperiod 16 h illumination /8h dark,temperature 28? and humidity 75%,the biomass of trifoliate decreased after 30 d waterlogging.The chlorophyll content of the leaves of trifoliate increased at the beginning of the waterlogging stage and decreased at the later stage.Citrus trifoliate showed more resistance to waterlogging.Alcohol dehydrogenase(ADH)activity and lactic dehydrogenase(LDH)activity decreased in the roots of trifoliate,indicating that in the process of waterlogging stress,trifoliate was adjusted by itself.Maintaining the intensity of anaerobic respiration pathway and providing energy for plant growth to maintain a certain amount of growth.Long term waterlogging will still cause energy deficit and accumulation of toxic and harmful substances such as ethanol and lactic acid,resulting in abnormal growth of plants and death.