Study On Physiological Response To Salinity Stress And Regulation Of Strawberry

Strawberry (Fragaria ananassa Duch.) is susceptible to salt stress. Effects of calcium salt and natrium salt stress on growth and physiological characteristic of strawberry were studied by soilless culture. Mechanism of salt damage relief of strawberry plant treated with deferent calcium, TFP, W7 and putrescine were also studied. Three strawberry cultivars, 'Toyonaka'(salt tolerant), 'Darselect'( middle salt tolerant) and 'Allstar'(salt sensitive) were used to investigate the salt tolerance of vary ages plant. Mechanism of salinity-tolerance of strawberry, the relation of calcium, putrescine and salinity-tolerance controlling were stated. The paper offered a scientific warranty for salinity-tolerance improving of strawberry. The main results were as follows:1.Growth of plants was suppressed by 150mmol . L^-1NaCl stress, at the meantime, relative electric conductivity, leaf proline content and chlorophyll a/b increased, chlorophyll content, photosynthesic rate(Pn) and transpiration rate(EVAP) decreased. Relative electric conductivity in root was more than that of leaf. The content of abscisin acid (ABA) increased, while the content of gibberellin(GA), Indoleacetic acid (IAA) and zeatin(ZT) decreased under salinity stress. Pphysiological activity, growth and salinity tolerance of Toyonaka were best, whereas Allstar was salt sensitive, Daselect was middle salt tolerant. Salinity tolerance of Biannual plant of three cultivars was better than annual plant.2.Relative electric conductivity increased following stress with Ca(NO₃)₂,CaCl₂ and Ca(AC)2,while leaf water saturation deficit increased, salt damage index and root/shoot increased with salt stress and salt concentration increasing, Water content, water holding ability, chlorophyll content, Pn, EVAP, stomatal conductance(GS),fresh weight and dry weight of plant decreased at the meantime. The salt damage caused by calcium salt was more than that of Natrium salt. There was more detrimental effects on growth treated with Ca(AC)2 than those with Ca(NO₃)₂ and CaCl₂. The damage caused by Cl" in strawberry was less than that of Na⁺ and Ca⁺ far away.3.Membrane damage in root and leaf of strawberry was relief by Ca(NO₃)₂,CaCl₂ and Ca(AC)₂ treatment under NaCl stress, while leaf holding ability and chlorophyll content was enhanced, growth was improved and the biomass increased. It is suggested thatcalcium play a role in reducing salt damage of strawberry, among the external calcium used in the experiment, Ca(NO3)2 was superior to CaC^ and Ca(AC)2 in reducing the salt injury.4.After pretreatment with Ca(NO3)2,W7 and TFP(trifluoperazine) in improving and blocking Ca2+ *CaM messenger system, membrane damage in strawberry leaf was relief by Ca(NO3)2treatment, at the meanwhile, salt damage index was reduced, the content of prolinc and chlorophyll were enhanced, Pn, EVAP and GS were improved, ABA content in root and leaf was reduced, the content of ZTJAA, GA and ZT/ABA were enhanced, the content of unaturated fatty acid(UFA) increased, whereas, saturated fatty acid (SFA) content in leaf and root was reduced, the rate between unaturated fatty acid and saturated fatty acid (U/S) and index of unaturated fatty acid(IUFA) were enhanced. The results suggested physiological bases of calcium mitigate NaCl stress in strawberry. Response of plants treated with calmodulin(CaM) antagonist TFP and W7 were reversed to those with Ca(NC?3)2.It showed Ca2+ ? CaM messenger system was involved in controlling salt stress resistance of strawberry plant, W7 was superior to TFP in blocking the forming of Ca2+ . CaM compound.5.After pretreatment with TFP, although the conductance of cultivate solution of strawberry seedling under NaCl stress was not increased, growth was inhibited obviously by TFP, while the leaf relative electric conductivity in strawberry increased, leaf holding ability was reduced. The inhibiting response increased with the concentration of TFP increasing. On the contrary, conductance in cultivate solution was increased by Ca(NC?3)2 treatment, but the leaf relative electric conductivity was reduced, leaf holding ability was enhanced, and the salt damage of strawberry seedling was relief. It indicated that Ca + was involved in controlling salt stress resistance of strawberry seedling.6.Membrane damage were relief by putrescine pretreatment, while growth of plants was improved and the biomass increased, salt damage mitigated, the accumulation of proline was enhanced, leaf water holding ability increased, the catabolism of chlorophyll was inhibited, Pn and EVAP increased, Fv/Fm, Fm/Fo and Fv/Fo rate increased, UFA,U/S and IUFA in root and roof increased, ABA content was reduced, while the content of ZTJAA and GA was enhanced, K+/Na+,Ca2+/Na+ rate were enhanced especially by putrescine and Cl" content was reduced. The results suggested physiological bases of calcium and putrescine mitigate NaCl stress in strawberry. The role of putrescine was promoted by calcium, whereas, was weaken overall or partly by calcium-deficient. It was suggested that putrescine was also involved in controlling salt stress resistance of strawberry plant and the role of putrescine was related to Ca2+ . CaM messenger system. The results showed that the content of linoleic acid(C18:2) and exadecylic acid(C16:0) was highest in strawberry root under salt stress, while the linoleic acid content was also highest in strawberry leaf. So, linoleic acid was determined as salt resistant indicator.