Effects Of Phosphorus And Potassium Ratio On Growth And Nutrients Absorption Of Cotton Seedlings

Phosphorus and potassium are two essential mineral elements for cotton seedling development,and their content is extremely important for cotton seedling growth and nutrient absorption and distribution.Phosphorus and potassium are two essential mineral nutrients for cotton growth and development.In order to explore the effect of phosphorus and potassium supply levels on the growth of cotton seedlings,HM 2270 used as the material,and was cultured in Hoagland complete nutrient solution in a temperature-controlled light culture room,and the concentration of other nutrients(including nitrogen concentration of 15.0 mmol L^-1)was fixed,set 3 phosphorus concentrations(low phosphorus 0.5 mmol L^-1（0.5P）,medium phosphorus 1.0 mmol L^-1（1.0P）,high phosphorus 2.0 mmol L^-1（2.0P）)and 3 potassium concentrations(low potassium 3.0mmol L^-1（0.5K）,medium potassium 6.0 mmol L^-1（1.0K）,high potassium 12.0 mmol L^-1（2.0K）),to examine the effects of 9 phosphorus and potassium combinations on the growth process and morphology,characteristics,nutrient uptake,and effects of soluble sugars,free amino acids,and soluble protein content of cotton seedlings.The main results are as follows:cotton seedlings in each treatment budded at the 8-leaf stage,and1.In morphological characteristics of cotton seedlings,the 1.0P0.5K treatment,the seedling height at budding was 42.32 cm（only lower than 2.0P2.0K）,the stem diameter was 4.66 mm,the total root length was 3188.91 cm,the root surface area was 276.34 cm²,and the root volume was 4.30 cm³,which were all larger than other treatments;Compared with the first-leaf stage,the leaf area expanded by 12.1 times at the time of budding,and the growth rate was the fastest.2.In cotton seedling biomass accumulation,at cotton squaring time,the cotton dry weight of leaf is more than that of stem which is more than that of root.The treatments with the largest dry matter mass of leaves,stems,roots and whole plants were 2.0P1.0K(1184.74 mg plant^-1),1.0P2.0K(819.62 mg plant^-1),and 1.0P0.5K(236.08 mg plant^-1),2.0P1.0K(2239.51 mg plant^-1).At 1.0P0.5K,the dry matter mass of leaves,stems,roots,and whole plant increased by 14.2,21.8,19.8,and 16.9 times,respectively,compared with the 1-leaf stage,and the growth rates were the fastest.3.The phosphorus and potassium contents of cotton seedlings increased with the increase of phosphorus and potassium.When budding,the nitrogen and phosphorus content of leaf is more than that of stem which is more than that of root.The potassium content of stem is more than that of leaf which is more than that of root.The leaf nitrogen content(52.94 mg plant^-1)at the 1.0P level was slightly less than the 0.5P level(54.96 mg plant^-1);the 1.0P concentration level had the highest nitrogen content in the stem(25.33mg plant^-1)and the root nitrogen content(6.61 mg plant^-1)),1.0P was the most favorable for nitrogen accumulation in cotton seedlings.4.In cotton seedlings,the contents of soluble sugar,free amino acid and soluble protein of leaf are is more than that of stem which is more than that of root.The soluble sugar content increased with the growth of cotton seedlings.The soluble sugar content(15.41 mg g^-1 FW)of leaves at 1.0P0.5K at budding was significantly higher than other treatments.When budding,the SPAD value of 1.0P0.5K leaves was 36.72（only less than2.0P1.0K）.In summary,cotton seedlings budded after the 8-leaf stage.Under the condition of nutrient solution culture,the phosphorus concentration of 1.0 mmol L^-1 combined with the potassium concentration of 3.0 mmol L^-1（1.0P0.5K）was beneficial to the growth of cotton seedlings,with the largest biomass,the most nutrient absorption and the best distribution.