Influence Of Methyl Jasmonate On Growth And Characteristics Of Salt Gland In Limonium Bicolor

Soil salinization is increasing seriously around the world and the area of saline soil iskeep increasing year by year. The food, economic and energy resources are facing direthreats. In China, it covers vast area of saline land, so how to improve and exploit thesaline land is an effective way to improve land use efficiency and promote theeconomic development. Recreto-halophytes have typical structures: salt gland and saltbladder, which can exclude excessive salt out to the environment to avoid the damageof salt stress on plants. If the fundamental mechanism of salt gland development andsecretion is known, the key salt tolerance gene will be cloned which can enhance thesalt tolerance of crops. This is one of the effective ways to develop and utilize salineand alkaline land.It is well known that plant growth and development can be regulated by planthormones. But there are few studies on the influence of plant hormones on secretionof salt glands. As a dominant species on Yellow River Delta, Limonium bicolor is atypical recretohalophytes with multicellular salt gland structure. Therefore, in thisthesis, Limonium bicolor was used to explore the effects of methyl jasmonate on saltsecretion characteristics and possible mechanisms of Limonium bicolor.The main results were as followings:1. Effect of different concentrations of NaCl treatment on growth, ion content and saltgland characteristics of Limonium bicolorBy determining the fresh and dry weight, water content, leaf area, ion content andother indicators under0,100,200and300mmol·L-1NaCl treatment, we found that100mmol·L-1NaCl promoted the growth of Limonium bicolor while the growth ofplant was inhibited under higher concentrations of NaCl treatment. Limonium bicolorcan grow normally under300mmol·L-1NaCl treatment. And the salt gland density, total number of salt gland, Na+secretion rate of single salt gland and Na+secretion ofsingle leaf were all increased with the increasing of NaCl concentrations.2. Effect of different concentrations of MeJA treatment on growth, salt gland densityand secretion rate of Limonium bicolorWhen Limonium bicolor was sprayed with low concentrations (0.01mmol·L-1) ofmethyl jasmonate, no significant effect on plant growth, salt gland secretion anddevelopment was detected. And plant growth was inhibited when concentrations ofmethyl jasmonate was increased, which was reflected by the reduction of biomass,water content, leaf area, chlorophyll content and photosynthetic rate, and the increaseof membrane permeability. At the same time, salt gland density and total number ofsalt gland were increased, but Na+secretion rate of single salt gland was decreasedwith the increasing of methyl jasmonate concentrations. Under MeJA treatment, therewas no significant effect on ion content of plants, which requires the reductions ofNa+secretion rate of single salt gland to keep Na+secretion of single leaf unchanged.3. Effect of different concentrations of MeJA treatment on growth, ion content andsalt gland characteristics of Limonium bicolor under NaCl treatmentThe Limonium bicolor under NaCl treatment was sprayed with differentconcentrations of methyl jasmonate. By comparing the fresh and dry weight, leaf area,ion content, chlorophyll content and photosynthetic rate between NaCl andNaCl+MeJA treatments, we found that MeJA enhanced efficiency of photosynthesisto relieve the inhibition of NaCl on plant growth and the most effective concentrationsof MeJA was0.03mmol·L-1. Compared with NaCl treatment, salt gland density, Na+secretion rate of single salt gland and Na+secretion of single leaf were also declinedunder NaCl+MeJAtreatment.4. Ca2+possibely involves the process of salt secretion of salt glandThe Limonium bicolor leaf disc secretion model was used to study effect of differentconcentrations of MeJA, calcium chelating agent EGTA and calcium influx inhibitorsLaCl3on the characteristics of salt gland secretion. The result showed that MeJAinhibited the secretion of salt gland in Limonium bicolor, while EGTA and LaCl3significantly alleviated the inhibitory effect of salt gland. Meanwhile, MeJA, EGTA and LaCl3had an impact on the secretion fluid volume of leaf discs and Na+secretionrate of single salt gland, however the Na+concentrations of secretion fluid was notsignificantly altered. This indicated that Ca2+was involved in the process ofMeJA-inhibited salt glands secretion. Referring to the stomatal movement regulatorymechanism and the salt gland secretion hypothesis, we hypothesized that MeJAactivated transmembrane Ca2+flux to change the cytosolic calcium concentration,then, calmodulin (CaM) or calcium-dependent kinases transferred JA signaling totrigger the expression of downstream genes, which inhibited vesicle-mediated saltsecretion of salt gland.