Research On Water Transportation Of Drought Stressed Tomato Root Systems And Tonoplast Aquaporins Expression Detection

Water flow throuht root system to shoots has three parallel pathways,apoplast through cell walls,symplast through the interconnecter,transcelluar must through cell membrane.A combintion of latter two is known as the cell to cell pathway .Water flow thought pathways varied from species ,root evelopment and water uptake character(osmotic pressures and hydrostatic). Symplast pathway and transcelluar pathway is difficultly distinguished by Experiment methods, and have no valid ways to make distinction between apoplast and cell to cell pathway. At present, water flow though transcelluar pathway in radial transportation is unclear, but more and more evidences show that there is large quantity water flow though cell membrane in root systems, intrinsic membrane proteins called aquaporins is a water-selective proteins.Aquaporins gene expression is not only regulated by factors of plant development and have tissue characters ,but response to water stress, drought, salinity, light ,ABA and nutrient deficit .Phosphorylation is a major mechanism used by cells as molecular switch to regulation protein activity. At present, water hydraulic conductivity research on vary pathways Q at plant tissue and cell level , and relationships between water channel and transcelluar pathway, is unclear.Using tomato seeding as experiment material under the water deficit condition, a pressure-flux approach was used to detect rate of water transportation and Lp of un-drought and dro-Stressed tomato root systems, when HgCh is served as aquaporins inhibitor. Root respiration and solution osmotic is also examined, which may affect on experiment data. At the same condition, tonoplast membrane aquaporins expression is detected by western blot. The following results were obtained.1. The results indicated that rate of water transportation of un-drought roots deceased46.7%,65.67% by 50,100 |imol HgCl2 treated , respectively , and recovery to 88.6%,80.59% by 500,1000 umol ME treated. In same conditions, rate of water transportation of dro-treated root deceased 40.67%, 58.82% correspondently by 50,100umol HgCl2 treated, and recovery to 79.41%,72.03%, by 500,1000 umol ME treated.The data above show that tomato root membrane has a large of mercury-sensitive channel aquaporins. Jv of drought root decrease and radial hydraulic resistance increase higher, which may be caused by quantity variety and activity of aquaporins . A large of population of water through root apoplast pathway at the higher hydrostatic condition.2.dro-stressed roots of Jv have obvious linear relations between 0.1 and 0.3 Mpa .and Lp is decresed with concentration of HgCl2 treatment increasing .Un-drouht roots of Jv have obvious linear relations between 0.1 and 0.5 Mpa. and Lp is decresed with concentration of HgCl2 treatment increasing . All these data and phenomenal above indicated that aquaporins existed dro-stressed roots and mediated water transportation.3. Experiment phenomenal of roots Jv were recovery by ME, roots respiration and osmotic detection data, which suggest that HgCl2 is not affect on experimental results .4. western blot experiment show that drought root hydraulic conductivity is not caused by variety quantity of tonoplast aquaporins.