Effects Of Different Rootstocks On The Growth And Root Development Of Root-cutting Grafted Watermelon Seedlings

Root-cut grafting is a new grafting method which has been widely used in watermelon cultivation.It shows fast grafting speed and high production efficiency.At present,the research of root-cut grafting technology of watermelon mainly focuses on grafting method optimization,but there are few reports on the rootstock screening,the physiological effect of root-cut grafting on plant,the regrowth process of adventitious roots,and the adventitious roots absorption mechanism of mineral nutrients.Therefore,in this study,“Zaojia 84-24”watermelon was grafted on 3 kinds of rootstock,which were“Jingxinzhen-2”squash,“Qinkangshuigua”gourd and“Yongshi”wild watermelon.By comparing root-cut grafting watermelon seedlings with top insertion of seedlings and self-root seedling,the suitable rootstock types for root-cut grafting of watermelon were screened out,and the advantages of root-cut grafting method were clear.The root tissue structure of root-cut grafting watermelon seedlings was observed to clarify the development process of adventitious roots after grafting.The absorption kinetics of N,P and K elements in grafted seedlings of different rootstocks were also studied to reveal the mechanism of mineral elements absorbed of watermelon grafted seedlings.The main results are as follows:1.All the three rootstocks could promote the growth of watermelon seedlings.Watermelon seedlings with“Jingxinzhen-2”squash rootstock showed the best growth by root-cut grafting and top insertion grafting method.“Qinkangshuigua”gourd showed the best affinity with watermelon scion,and high grafting survival rate.Watermelon seedlings with Qinkangshuigua rootstock grew better than with Yongshi rootstock.And watermelon seedlings with“Yongshi”wild watermelon rootstock showed the best photosynthesis.2.Adventitious root primordium of the three rootstocks belonged to induced root primordium,which originated from the cambium in the vascular bundle.And the rooting mode was dermal rooting type.However,the rooting speed of the adventitious root primordium was different among the three rootstocks,which showed Jingxinzhen-2>Qinkangshuigua>Yongshi.3.Root-cut grafting seedlings had a weaker root system than that top insertion of seedlings in the early stage.With the development of adventitious roots,the root-cut grafting seedlings showed better roots growth in the late stage of grafting.The results showed that the root-cut grafting seedlings with Jingxinzhen-2 rootstock had the best developed root system and root activity,followed by the Qinkangshuigua rootstock and Yongshi rootstock.4.The roots of different rootstocks had different absorption kinetics characteristics of N,P and K elements.Compared with the self-root seedling,the affinity of root for N,P and K was enhanced after grafting.The affinity of root system for NO₃^-absorption of the three rootstocks root-cut grafting seedlings was higher than that of the top insertion of seedlings,which showed Jingxinzhen-2>Qinkangshuigua>Yongshi;The affinity of root system for NH₄⁺absorption of root-cut grafting seedlings was higher than that of the top insertion of seedlings,which showed Qinkangshuigua>Jingxinzhen-2>Yong Shi;The affinity for PO₄^3-absorption of the root system of Jingxinzhen-2 and Qinkangshuigua root-cut grafting seedlings was higher than that of the top insertion of seedlings,but the affinity for PO₄^3-absorption of the root system of Yong Shi root-cut grafting seedlings was lower than that of the top insertion of seedlings;The affinity of root system for K⁺absorption of root-cut grafting seedlings was higher than that of the top insertion of seedlings,which showed Jingxinzhen-2>Yong Shi>Qinkangshuigua.In summary,Jingxinzhen-2 is the best watermelon rootstock for root-cut grafting method,and it is suitable for watermelon production.