Study On Salt Resistant Mechanism Of Malus

Using seedlings of Malus baccata, M. xiaojinensis and M. zumi with different salt-tolerance as the experimental materials, physiological and biochemical mechanism of Malus was comparatively studied. The results showed that the main Na+exclusion localization of Malus was roots and stem base, and Na+ exclusion capability in roots and stem base of salt-tolerant species was obviously higher than that of salt-sensitive ones. Whole Na+exclusion capability of salt-sensitive species was about 65 %, middle salt-tolerant species about 80 %, salt-tolerant species about 90 %. Whole Na+exclusion capability and Na+ restriction capability of salt-tolerant species were all obviously higher than that of salt-sensitive ones. Salt-tolerant species could efficiently restrict Na+from transporting to shoot. Lateral roots, stem base xylem and old leaves of salt-tolerant species obviously occurred Na+ accumulative effect, and were main Na+ accumulative localizations. SK. Na (吸收) and Sk. Na (运输) of salt-tolerant species were all obviously higher than that of salt-sensitive ones. It indicated that K-Na selective uptake and transport capability of salt-tolerant species were obviously higher than that of salt-sensitive ones. Leaves Na+ / K+ ratio of salt-tolerant species became lower than that of salt-sensitive ones in the end.Root 22Na treatment experiment showed that landscape orientation transport of 22Na existed in stem base of Malus. Through accumulating more 22Na in roots (especially in lateral roots) and higher 22Na transport rate of stem base phloem, salt-tolerant species efficiently restricted 22Na from transporting to shoot. Leaves 22Na feeding experiment showed that the amount of 22Na absorbed by leaves of salt-tolerant species was obviously higher than that of salt-sensitive ones, and leaves 22Na content of salt-tolerant species decreased more than that of salt-sensitive ones. It indicated that leaves of salt-tolerant species had higher re-transport capability of 22Na to underground part, and helped to reduce the shoot 22Na content of salt-tolerant species. 22Na and NaCl split-root experiment showed that salt-tolerant species had higher salt extrusion capability of roots and higher whole recirculation amount of salt, which made its salt content of shoot even less.Root H+-ATPase activity, proton pump activity and Na+ / H+ antiport activity of plasmolemma and tonoplast in Malus were all obviously increased under salt stress, and salt-tolerant species increased more. Under same salt concentration treatment, H+-ATPase activity, proton pump activity and Na+ / H+ antiport activity of plasmolemma and tonoplast in salt-tolerant species were all obviously higher than that in salt-sensitive ones. Higher H+-ATPase activity and proton pump activity would help salt-tolerant species to construct the proton electrochemical gradient across the plasmolemma and tonoplast in saltstress, and well supplied energy to Na+ / H+antiport of plasmolemma and tonoplast. Higher Na+ / H+ antiport activity of plasmolemma and tonoplast in salt-tolerant species would help to extrude and compartmentalize Na+ in roots in salt stress.The increased multiples of H+-ATPase activity, proton pump activity and Na+ / H+ antiport activity of Mains in three salt concentration treatment were all obviously higher than that in same osmotic PEG treatment, especially, salt-tolerant species increased more. It indicated that sodium ion effect had greater stimulation in H+-ATPase activity, proton pump activity and Na+ / H+ antiport activity of salt-tolerant species.Salt-tolerance of Malus showed negative correlation with accumulation of free proline and soluble sugar in main roots, lateral roots, young leaves and mature leaves. Free proline and soluble sugar content of salt-tolerant species had an adaptable increase in salt stress, but that of salt-tolerant species accumulated less and had lower variety ratio. We presumed salt-tolerant species should carry osmotic adjustment mainly through abio-ions. Abundant accumulation of free proline and soluble sugar...