Effects Of Drought Stress On Growth, Physiological And Spectral Characteristics In Cotton Seedings

The effect of grouth, photosynthetic character and spectral signature parameter werestudied with different Bt transgenic cotton cultivar (Nongdamian8and Lumianyan28),this experiment was studied with two ways in the training room of he agriculturaluniversity of Hebei in the year of2012and2013, which include the pot culture and PEG-6000solution. The nomoral irrigate(CK), milddle stress (LS), moderate stress (MS), severestress (SS) and extreme stress (ES) was designed by the pot culture. The solution cultureexperiment set the concentration as CK,1.5%,3%and4.5%of four levels. The responseof leaf water potential, leaf relative water content, SPAD and photosynthetic parameters,chlorophyll fluorescence parameters and spectral signature parameter under differentdrought stress of cotton seedings. The results showed that:1. In the cultivation of pot, the growth of cotton seedling was significantly inhibitedby the drought stress. With the increase of drought stress, the height, leaf number, leaf areaand stem diameter decreased, the root-shoot ratio increased, the relative water content ofleaves and leaf water potential decreased. The leaf relative water content of treatment ofstress was lower than CK, the variety of Nongdamian8decrease respectively by10.3%,10.0%,12.1%and20.0%, the leaf water potential fell by13.0%,23.5%,34.6%and13.0%respectively. The leaf relative water content of treatment of stress the variety ofLumianyan28reduced respectively by8.2%,14.3%,11.2%and30.9%, leaf water potential,fell by7.2%,19.1%,27.0%and40.5%respectively, the growth indexes can reflect thestatus of cotton seedlings.2. In the cultivationof pot, the water stress resulted in progressively decrease in netphotosynthetic rate (Pn), Light use efficiency (LUE), maximum photosynthesis efficiencyof PSⅡ(Fv/Fm), the actual photosynthesis efficiency of PSⅡ in the light (φPSⅡ) andphotochemical quenching (QP), but increase in limiting value of stomata(Ls), Water UseEfficiency (WUE) and the nonphotochemical quenching (NPQ). On the whole, there weresignificant differences in Pn and NPQ among MS、SS、ES and CK, From LS to SS, the average Pn decreased by11.5%,18.1%,32.1%and38.1%, While compared with CK, theNPQ increased correspondingly by24.1%,50.9%,79.4%and145.1%. The experimentsindicate that light water stress has little effect on photosynthetic character at cottonseedling stage, but higher extent of water stress (higher than middle stress) will result inthe decline of photosynthetic capacities of PS II.3. The response of photosynthetic parameters on photosynthetic active radiation isdifferent under different cotton seedlings of PEG-6000drought stress treatment.With thedegree increase of drought stress, the response of the light curve of Pn, Ls and WUE to theincrease of light has fallen dramatically. Compared with CK, the value of Pnmax ofNongdamian8fell by17.0%,45.7%and73.0%, respectively, the Lumianyan28has fallenby48.9%,34.1%and68.0%, respectively. With the increase of the degree of drought stress,the light saturation point (LSP) of both the cotton varieties has decreased and the lightcompensation point (LCP) increased.4. The original spectral characteristics of cotton seedlings in the different cultivationshave the same change trend. In the scope of500-600nm and600-950nm band, thespectral reflectance of CK treament is the highest, the treatment of ES and SS is the lowest.The response of the parameter index to the water stress is different under the different wayof cultivation and the different cotton varieties of seedling. In the way of potted plant, thecorrelation between spectral indices PRI and FWC has reached extremely significant levelin varieties, the correlation between spectral indices WI、WBI and FWC has reached above0.4in variety of Nongda8and is lower than0.4in the variety of Lumianyan28; In the wayof PEG-6000solution, the correlation of ND、R/ND with RWC has reached above0.6inboth varaities. Therefore, The spectral index of ND, R/ND and PRI is sensitive andaccurate about the response to drought stress under water deficit under different trainingmodes and different varieties.