Studies On Salt Tolerance Characteristics Of One Year Old Transplanted Seeldings Of Black Mulberry Under NaCl Stress

In this study, one year old transplanted seedlings of Black Mulberry were used as the experimentmaterial, and their changes on physiological characteristics under NaCl stress were studied, in order tounderstand their salt tolerance characteristics. As randomized complete block experiment was designed,0(CK),50,100,150,200,250,300mmol·L-1seven different levels of soil salinity were prepared, samplessalt treatment for12d were taken to study their responses such as cell conductance, MDA, soluble sugar,soluble protein, SOD, POD, photosynthesis and fluorescence characteristic parameters, Na+、K+ion contentand root activity. Use the mathematical methods of variance analysis to study their response characteristicsto different concentrations of NaCl treatment. The main conclusions are as follows:1NaCl stress had certain toxic effects of ions on one year-old transplanted seedlings of BlackMulberry, mainly the large number accumulation of Na+in plants; the decrease of K+in plant organs; therapid increase of Na+/K+value. Under different concentrations of NaCl treatment, one year-old transplantedseedlings of Black Mulberry showed the effect of Na+regionalization. Under50,100,150mmol L-1NaCltreatment, the order of Na+content in plant organs was root>stem>leaf, which was the main feature of theion segment; And when NaCl concentration was200mmol L-1, the content of Na+in leaf was greaterthan the roots and stems. The plant had been significantly hurt. On the12th dealing day, the leaves of plantswilted and withered and soon all fell off. Rapid increase of Na+content in the leaves of the plant was themain reason for the victims; the falling of leaves under high salt environment was their adaptation to saltstress for one way of Na+efflux. Under salt stress, the content of Na+in the leaves was the most abundant,followed by stems, and roots was the lowest.So, leaf was the main site of damage by salt in BlackMulberry.2NaCl stress had certain degree damage on the integrity of the cell membrane structure and functionof the one year-old transplanted seedlings of Black Mulberry, mainly the decline of relative water contentin leaf, leaf wilt; the decrease of root activity; the increase of membrane permeability and MDA content.Under50mmol L-1NaCl treatment, there was no significantly different between it and CK on RWC,membrane permeability and MDA levels, and root activity was significantly higher than CK, showing theresistance characteristics to salt of one year-old transplanted seedlings of Black Mulberry to some extent.3NaCl stress significantly reduced the photosynthetic capacity of the one year-old transplantedseedlings of Black Mulberry. With the increasing concentration of NaCl, Gs, Tr, WUE, Pn decreased, while Ci increased, energy conversion efficiency and photosynthetic capacity in leaves of Black Mulberry fall.Under50mmol L-1NaCl treatment, there was no significant difference between it and CK on netphotosynthetic rate level of one year-old transplanted seedlings of Black Mulberry,and slightly higher thanCK,showing the photosynthetic capacity of one year-old transplanted seedlings of Black Mulberry underlow salt.to some extent. When NaCl concentration≥100mmol L-1, the photosynthetic capacity of BlackMulberry had received a strong inhibitory effect, and with the increase of NaCl concentration, the degree ofinhibition was increasing and the effects of reducing Pn of one year-old transplanted seedlings of BlackMulberry primarily controled by non-stomatal factors. As the NaCl concentration increasing, the limitinginduced by non-stomatal factors played a more obvious role. In addition, NaCl stress had a significanteffect on chlorophyll fluorescence parameters of one year-old transplanted seedlings of Black Mulberry.Under50mmol L-1NaCl treatment, there was no significant difference between it and CK on ΦPS, qP,ETR and Fv ’/Fm’ levels, but with the NaCl concentration increases, ΦPS Ⅱ, qP and ETR showed adownward trend, and the higher the concentration, the more obvious the decline.4Under NaCl stress, the activities of SOD, POD and CAT of one year-old transplanted seedlings ofBlack Mulberry did not present a single trend. At low concentrations (50mmol L-1) NaCl treatment, theactivities of SOD, POD and CAT was increased compared with CK. When NaCl concentration≥100mmolL-1, the activities of SOD and CAT did not change singly, POD activity decreased significantly. Under200mmol L-1NaCl deal, which SOD, CAT activity still remained CK’s89.5%and83.5%respectively,indicating that the antioxidant enzyme systemcan reduced or alleviated the persecution of NaCl stress onone year-old transplanted seedlings of Black Mulberry to some extent.5Under NaCl stress, the content of soluble sugar in leaves of one year-old transplanted seedlings ofBlack Mulberry did not present a single trend, but the overall rose and fell again after the first rose. Withincreasing of NaCl concentrations, the content of soluble protein increased first and then decreased.Although both content had a downward trend under NaCl stress, but it changed slightly and remained at ahigh level. Under300mmol L-1NaCl stress, the content of soluble protein was relatively stable, stillremained CK’s79.8%, showing a strong adaptability to salt.