Effect Of Nitrogen Fertilizer On The Yield And Starch Quality Of Lotus Root

Nelumbo nucifera Gaertn,also known as lotus root,lotus and water hibiscus,is a perennial herb of lotus family.Lotus root,originated from China and India,is the largest aquatic vegetable variety in China.It has good edible and medicinal value and is loved by consumers.Lotus root is rich in starch,protein,amino acids and various vitamins.And starch is the main storage material of lotus root,generally accounting for 10%～20%of fresh weight.Its structure and content affect the edible and processing quality of lotus root.Among all the essential nutrients in crops,nitrogen is an important factor affecting crop growth and yield formation,and also plays a key role in regulating the processing quality of starch crops.The use of nitrogen fertilizer in Lotus production in China is still unclear,and the phenomenon of excessive application of nitrogen fertilizer occurs from time to time,which not only leads to the increase of production cost,but also causes the waste of resources,environmental pollution and other problems.In addition,the regulation mechanism of nitrogen fertilizer on Lotus Starch is still unclear.Therefore,it is of great significance to study the effects of nitrogen on starch quality and starch synthesis genes of lotus root for establishing high-quality and high-yield cultivation techniques and promoting the development of lotus root industry in China.In this experiment,the effects of different nitrogen rates on photosynthetic characteristics,yield,starch content,quality and related genes of lotus root were studied.The main results are as follows:1.The effect of nitrogen fertilizer on photosynthesis of lotus root.Net photosynthetic rate,transpiration rate,intercellular CO2 concentration,stomatal conductance and total chlorophyll content were measured.The results showed that nitrogen fertilizer could increase the total chlorophyll content of lotus root,promote the increase of stomatal conductance,intercellular CO2 concentration and transpiration rate,and thus increase the net photosynthetic rate.The photosynthetic rate reached the highest level at 30 kg/667m2 of nitrogen fertilizer,and excessive application of nitrogen fertilizer would lead to the decrease of photosynthetic rate.Proper application of nitrogen fertilizer can improve the yield of lotus rhizome,and the yield is the highest when the amount of nitrogen fertilizer is 30 kg/667m2.But,excessive application of nitrogen fertilizer can reduce the yield of lotus root.2.The effect of nitrogen fertilizer on the starch characteristics of lotus root.Nitrogen fertilizer can promote the increase of total starch,amylose and amylopectin content of lotus root.When the nitrogen fertilizer dosage is 30 kg/667m2,the total starch and amylose content reach the maximum;When the nitrogen fertilizer dosage was 20 kg/667m2,the amylopectin content reached the maximum.The excessive application of nitrogen fertilizer will lead to the decrease of total starch,amylopectin and amylopectin content.With the increase of nitrogen fertilizer,the ratio of amylose to amylopectin content is increasing.The number of long oval starch grains increased with the increase of nitrogen fertilizer,while the number of near round starch grains decreased,and the ratio of the number of long oval starch grains to the number of near round starch grains increased.When the nitrogen fertilizer dosage is 50 kg/667m2,the ratio of the long oval starch to the near round starch granules is 2.3;The control was only 1.1,which was significantly lower than that of nitrogen application.The results of starch viscosity analysis showed that nitrogen increased the peak viscosity,hot pulp viscosity and disintegration value of lotus root starch,reduced the temperature of reducing impairment and gelatinization,and reduced the peak time.Nitrogen fertilizer increased the number of short chain of amylopectin,reduced the number of long chain,and increased the branching degree of amylopectin.3.Transcriptome analysis of lotus root starch synthesis regulated by nitrogen fertilizer in.The transcriptome of lotus root rhizomes treated with 0 kg/667m2 and 30 kg/667m2 was analyzed.KEGG enrichment analysis showed that the differentially expressed genes were mainly enriched in starch and sucrose metabolism,carbon metabolism,amino acid biosynthesis,phenylpropanoid biosynthesis,fatty acid biosynthesis,glyceride metabolism,galactose metabolism,flavonoid biosynthesis and other metabolic pathways.Go enrichment analysis showed that differentially expressed genes were mainly enriched in biological metabolism process,cellular process,stimulation response,biological regulation,catalytic activity and transcriptional activity.A total of 12 differentially expressed genes were screened from starch and sucrose metabolism pathways and verified by qRT-PCR.The results showed that 11 genes were significantly up-regulated under nitrogen fertilizer regulation,including SUS、INV、GPI、UGP2、APS2、GBSS、SBEI、SBEII、AMY3、BAM3 and DPEP.