Effects Of Allelopathy Fatty Acid Esters On Physiological Characteristics And Mineral Element Content Of Own-rooted And Grafted Watermelon

This experiment was used the watermelon ’Zaojia 84-24’ as the test material to study the effects of allelochemicals diisobutyl phthalate(DIBP)and dioctyl phthalate(DOP)at different concentrations(0,0.05,0.1,0.5,1,4 mmol·L-1)on root physiological characteristics and mineral element content of self-rooted watermelon seedlings.At the same time,two kinds of gourd varieties(’Jingxin rootstock’ and ’Zhen Qiu’)and two kinds of pumpkin varieties(’Japanese Cedar’ and ’Jiuzhen No.1’)were used as rootstocks,and ’Zaojia 84-24’ watermelon as scion,to study the effects of 4 mmol·L-1concentration of DIBP and DOP on the roots physiological characteristics and mineral element content of grafted watermelon seedling.The following results are obtained:(1)After treating watermelon seeds with different concentrations(0,0.05,0.1,0.5,1,4mmol·L-1)allelochemicals diisobutyl phthalate(DIBP)and dioctyl phthalate(DOP),The germination rate of watermelon seeds reached the maximum when the treatment concentration was 0.1 mmol·L-1,and then decreased with the increase of treatment concentration.Under DIBP treatment,the number of watermelon root border cells was significantly higher than that of the control.The survival rate of marginal cells and PME activity reached the maximum at the treatment concentrations of 0.5 mmol·L-1and 0.1 mmol·L-1,respectively.And then gradually decreases with the increase in concentration.After DOP treatment,the number of watermelon root border cells,border cells survival rate,and PME activity all increased first and then decreased.At 4 mmol·L-1treatment concentration,the border cells survival rate was significantly lower than the highest value of 12.56%(P <0.05).It shows that low concentration of fatty acid ester treatment can promote the production of root border cells and protect plant root tips.When the concentration is too large,it will reduce the activity of marginal cells and damage plant root tips.(2)After treatment with different concentrations of DIBP and DOP,watermelon root dehydrogenase activity,root SOD activity,POD activity,CAT activity,and nitrate reductase(NR)activity all showed a trend of increasing first and then decreasing.The content of aldehyde(MDA)and soluble protein increased with increasing treatment concentration.There was no significant difference in the root length of watermelon under the treatment of DIBP at all concentrations,only significantly lower than the treatment at the concentration of 4 mmol·L-1(P<0.05).Under the treatment of DOP at each concentration,the root length of watermelon increased the trend of post-decrease was significantly lower than the control at the treatment concentration of 4 mmol·L-1.It shows that low concentration of fatty acid ester treatment can improve the antioxidant activity of plant roots.At the same time,the plant will also promote the production of its own osmotic adjustment substances to maintain the normal physiological activities of plant root cells.In addition,DOP has stronger self-toxic effects than DIBP.(3)After treated with different concentrations of DIBP and DOP,the content of mineral elements in watermelon roots will change with the concentration.The content of Ca,K and Mg in root system of watermelon seedlings will change after DIBP treatment,but there is no obvious change rule.The content of Cu and Zn will increase under low concentration treatment,while the content of Fe will decrease first and then increase with the increase of treatment concentration.With the increase of DOP concentration,the content of Fe and Zn in watermelon roots decreased first and then increased,while the content of Mg and K increased first and then decreased.It indicated that under the treatment of different allelochemicals and different concentrations of allelochemicals,the absorption and accumulation of mineral elements in watermelon roots would change,so as to resist external damage and maintain normal physiological activities of watermelon.(4)Under a certain concentration of DIBP and DOP,after grafting on different rootstocks(’Jingxin rootstock’,’Zhen Qiu’,’Japanese Cedar’,and ’Jiuzhen No.1’),the overall growth potential of the plant root system is that the own-rooted seedlings are lower than the gourd grafted seedlings,and the pumpkin grafted seedlings have the strongest growth potential,but the root dehydrogenase activity of gourd grafted seedlings is higher than that of pumpkin grafted seedlings,indicating that the roots of pumpkin grafted seedlings are more sensitive to fatty acid ester compounds.In addition,the root SOD activity and CAT activity of the gourd grafted seedlings were higher than the pumpkin grafted seedlings,and the root POD activity of the grafted seedlings was significantly higher than that of the own-rooted seedlings.The content of malondialdehyde(MDA)in the root system as a whole was higher than that of pumpkin seedlings,and the content of grafted seedlings of gourd was the lowest,while the root soluble protein content was only significantly higher in grafted seedlings of ‘Jingxin rootstock’ and‘Jiuqzhen No.1’ than own-rooted seedlings,The Nitrate reductase activity of grafted seedlingswas higher than that of own-rooted watermelon as a whole.Moreover,the absorption and accumulation ability of Mg and K in grafted watermelon was stronger than that in self rooted watermelon,and the content of K in root system was as follows: cucurbit grafted seedlings >pumpkin grafted seedlings > own-rooted seedlings.After the watermelon is grafted,the root system of the grafted watermelon has good anti-poisoning properties the characteristics of selective absorption and accumulation of mineral elements of the rootstock.the growth potential of the pumpkin grafted seedlings is stronger than that of the gourd grafted seedlings,but the resistance of the gourd grafted seedlings is stronger than that of the pumpkin grafted seedlings,of which the ’Jingxin rootstock’ graft seedlings have the strongest anti-self-poisoning properties.