Studies On Root Growth Dynamic And Nutrient Metabolism Of Cotton Seedling By Floating Nursing Seeding In Nutrient Water-bed (FNSNWB)

F1hybrid of Jinnongmian used as experimental material, length of main root, number of lateral root, root weight, growth dynamic as well as asorption and utilization characteristics of mineral element N, P, K of cotton seedling by FNSNWB method. The main results are as follows:1The growth dynamic of the lateral root of cotton seedlings.The taproot elongated around16hours after sowing and its length grew from3cm to5cm after24hours. The root primordium can not be observed outside the cambial layer of the taproot at2days after sowing. However, it tended to be apparent in3DAS (days after sowing). Some of them extended and nearly3to5first lateral roots were formed. Moreover, the secondary lateral roots grew out at9DAS.2The increasing dynamic of taproot.With suitable sowing depth, the taproot's length of cotton seedling by FNSNWB method in1to9DAS increased according to S-figure curve, which was fitting for and significant level of this fitting model reached at1%.3The increasing dynamic of dry weight.The germination rates of the root system with lcm,2cm,3cm, and4cm sowing depth were above85%at3DAS. Dry weight increased with cotyledons' flatten and roots'unearthed, the rate of increase decreased even slightly dropped at6DAS. The trough appeared at9DAS and then increment sped subsequently.4The increasing dynamic of the root areas.As the number of days increased after sowing, the root areas of cotton seedling changed greatly. Under the suitable sowing depth, the increase of root areas can be divided into two stages:rapid growth and steady growth,3DAS to6DAS belongs to the first stage whereas6DAS to9DAS falls into the second stage.5The suitable sowing depth of cotton seedlings.The research indicated that the suitable sowing depth of cotton seedling by FNSNWB was1to2cm, which was favorable for the growth of taproot and lateral roots, benefit the increase of dry weight as well as root areas. So the suitable sowing depth can be considered as a key cultivating practice of cotton seedlings.6Whole-plant N, P, K content of cotton seedling at first true leaves stage.The research proved that whole-plant N, P content of cotton seedlings by FNSNWB are higher than those of control at first true leaves stage, and the differences are significant (P<0.05). Whereas whole-plant K content by FNSNWB was significantly lower than the control. Whole-plant N, P content by FNSNWB increased with the rise of fertilizer levels,and the differences among different fertilizer level were obvious, highest content of N, P was in treatment4, next was treatment3, then treatment2, last one was treatment1. The order for all4treatment of all strains by FNSNWB according their total K content was1<4<2<3.7Whole-plant N, P, K content of cotton seedling at second, third and fourth true leaves stage.Whole-plant P content in other3treatment by FNSNWB were higher than those of controls and differences are significant (P<0.05) except in treatment3. With the growth of cotton, whole-plant N content by FNSNWB were significantly higher than the control (P<0.05) at third true leaves stage. Whereas whole-plant P content in all3treatment were higher than the control and there is a statistically significant difference (P<0.05) except in treatment1. When fourth true leaves developed, there was no remarkable difference of whole-plant N, P content between FNSNWB and control in treatment1, while whole-plant N, P contents by FNSNWB were significantly higher than that of the control (P<0.05) in all other3treatments. Whole-plant K content by FNSNWB was lower than that of the control in all4treatment and the differences are significant (P<0.05).8The dynamic change of N, P, K content under different seedling age.FNSNWB, the new seedling method can raise fertilizer concentration in nutrient liquid, promote the nutrient absorption of cotton seedlings, and accelerate transportation of nutrient elements on the ground portion. This research showed that, whole-plant N, P, K content decreased with the growth of seedlings in treatment1. From first true leaves stage to third true leaves stage, whole-plant N and P content increased to a maximum value and followed by a declining trend at second true leaves stage in treatment2and3, and they increased according to straight line curve in treatment4. From first true leaves stage to fourth true leaves stage, whole-plant K content decreased in a linear trend in treatment1,2and3, and also increased in linear trend in treatment4.