Ion transport and distribution in three grape strains under salt stress

FU Qingqing; TAN Yazhong; ZHAI Heng; DU Yuanpeng

doi:10.13925/j.cnki.gsxb.20170188

Abstract：[Objective] Soil salinization is an important environmental problem that restricts agricultural development and crop growth.High saline and alkaline soils cover approximately 36 million hm2 of land in China,and accounts for approximately 1/3 of the total saline-alkaline land in Asian.In China,saline and alkaline lands are chiefly distributed in the northern arid,semi-arid and semi-humid areas,and those in Xinjiang account for about a third of the total cultivated land.Grape plants have strong salt tolerance compared with other fruit trees,but the salinity tolerance of Vitis labrusca is generally lower than that of V.vinifera.‘Beta’ is a widely used rootstock,but its salt tolerance is weak,and rootstock 1103P also can not satisfy the needs of production either.So it is important to breed salt-resistant rootstocks with cold hardiness to solve the ecological problem in northwest grape-producing areas.In our previous study,the salt tolerance of hybrids (V.amurensis ‘Zuoshan’ × SO4) with cold hardiness and phylloxera resistance were evaluated,and rootstock 1103P was used as the control.The results showed A34,A35,A15 and A17 had strong salt tolerance;A38,A48 and B24 had medium salt resistance;and the salt resistance of 1103P and B26 were weak.In this study,ion transport and distribution of A17,A38 and 1103P under 100 mmol· L-1 NaC1 treatment were studied.[Methods] One-year-old cuttings of A 17,A38 and rootstock 1103P were planted in pots (diameter 17 cm,height 25 cm) containing mixture of soil,sand and peat (2∶ 1∶ 1).When the plants had 8-10 fully expanded leaves,some of the plants were irrigated with 1 000 mL 100 mmol·L-1 NaCl every 3 days at 5:00-6:00 pm,while the other plants irrigated with water as the control.The contents of ions in roots,stems and leaves of each strain were determined after 20 days of stress treatment.A17,A38 and rootstock 1103P in vitro were used to study the Na+ net flow in root system.Plants were cultured in 30 mL MS liquid culture medium for 2 days,and then transferred to 30 mL MS liquid culture medium containing 100 mmol·L-1 NaCl.The control plants were transferred to 30 mL MS liquid culture medium without NaCI.Six individuals were used for each treatment.Na+ net flow in root system was evaluated using NMT (non-invasive micro-test technique) after 24 h of NaCl treatment.The site examined was located at 600 μm from the root tip,where vigorous Na+ fluxes were usually observed with 6 root tips from 6 individuals for each treatment.Na+ net flow in root system was traced for 10 min.Flux was calculated using Fick's law of diffusion:J=-D×(dc/dx),where J represents the ion flux in the x direction,dc/dx the ion concentration gradient and D the ion diffusion constant in a particular medium.The data acquisition,preliminary processing,control of the three-dimensional electrode positioner and stepper motor-controlled fine focus of the microscope stage were performed with the MageFlux software,which was part of the NMT system.The Na+ fluxes were measured for 10-12 minutes.Na+ fluxes were calculated using MageFlux software.[Results] Under 100 mmol· L-1 NaCl treatment,the contents of Na+ in the leaves and whole plant of strain A17 with strong salt-tolerance were the lowest and 4 and 2.24 times of the control,respectively.Na+ efflux ability of A17 was high (1 513 pmol· cm-2· s-1) and Na+ interception in root was 53.21％.Na+ in organs above ground of A17 was low (3.63 times of control).The contents of Na+ in the leaves and whole plant were the highest in 1103P,which were 14.65 and 2.86 times of the control,respectively.Na+ efflux ability of 1103P was low (863 pmol· cm-2· s-1);Na+ interception in root of 1103P was 29.14％,and Na+ in organs above ground was 5.42 times of control.The ratios of K+/Na+,Ca2+/Na+ and Mg2+/Na+ in leaves in saltresistant strain were higher.The SK.Na value of A17 increased after 100 mmol· L-1 NaCl treatment;SCa.Na and SMg.Na of A17 had no significant difference with control;SK.Na,SCa,Na and SMg.Na of 1103P and A38 decreased after salt treatment,indicating that the selective transportation of K+,Ca2+ and Mg2+ to organs above ground was decreased in the two strains by NaC1 treatment,while the selective transportation of K+,Ca2+ and Mg2+ to organs above ground of A 17 was higher.[Conclusion] The results showed that the rootstocks with strong salt tolerance absorbed less Na+,had stronger Na+ efflux and Na+ interception ability,which reduced the accumulation of Na+ in the leaves and maintained ion balance in plants.