适用于低钾条件下棉花苗期根冠通讯研究的三种嫁接方法

Three Types of Grafting Techniques Available for Research of Root-Shoot Communication in Cotton(Gossypium hirsutum) Seedlings under Low-Potassium Condition

为了满足棉花叶片衰老(以缺钾诱导)过程中根冠通讯研究的需要,在营养液培养条件下探索了棉花子叶期至一叶期幼苗的单接穗单砧木嫁接、双接穗单砧木(Y型)和单接穗双砧木(A型)嫁接技术。通过研究营养液中钾浓度、砧木和接穗的苗龄配合、嫁接部位及砧木保留子叶对嫁接成活率的影响,综合考虑嫁接成活率和成活后用缺钾诱导嫁接苗衰老的速度,确定单接穗单砧木嫁接和Y型嫁接的砧木均在不含钾的沙床中出苗后(萌发后3d)转移至钾浓度为0.1mmolL-1(中度钾胁迫)的1/2改良Hoagland营养液中培养5d至第1片真叶出现,接穗在不含钾的沙床中出苗后(萌发后3d)再生长2d,采用砧木留子叶法在子叶节处嫁接。A型嫁接的适宜条件和方法为砧木和接穗苗龄(第1片真叶刚出现)相同,嫁接前的培养方法同Y型砧木,嫁接部位在砧木子叶节下2～3cm处。单接穗单砧木、Y型和A型嫁接的平均成活率分别可达到95%、85%和90%以上。

Grafting have been widely used to limit the effects of soil and vascular diseases, to increase yield and fruit quality, to induce resistance against low and high temperatures, to enhance nutrient uptake and to study the shoot-root relationship. Up to now, the main objectives of cotton grafts are to propagate somatic regenerated plants, transgenic plants and rare germplasm mate- rials etc., and almost not come down to the research on long-distance signaling in plant. Recently, premature senescence caused by low potassium （K） has become one of the constraints for high yield and fine quality in cotton production. Before using grafting as a tool to investigate the shoot-root communication during this course, applicable grafting methods should be developed firstly. Therefore, we established normal （one scion and one rootstock）, Y-type （two scions and one rootstock） and A-type （one scion and two rootstocks） grafting techniques with cotton seedlings （before one-leaf stage） grown in hydroponic condition. The effects of K^＋ concentration in culture solutions, difference of scion age and rootstock age, different grafting sites and remaining cotyledons of rootstock or not on the survival rate of grafted cotton seedlings were examined. Considering either high survival rate or fast inducement of leaf senescence by low-K after grafting, the following methods were applicable for normal and Y-type grafting： the rootstocks emerged （3 days after germination） in sands without K, were transferred to one-half strength modified Hoagland solu- tion containing 0.1 rnmol L-1 K^＋ （moderate K deficiency） and cultured for 5 days to just appearance of the 1st true leaf; the scions were grown only in sands for 5 days after sowing with fully expanded cotyledons and grafted in cotyledon node of rootstocks with their two cotyledons remained. For A-type grafting, the applicable procedure was as followings： the scions and rootstocks were all cultured with the same procedure for normal and Y-type graftings, the scion was grafted in the part of 2-3 cm below cotyledon node of rootstock. The mean survival rates of normal, Y-type and A-type graftings were more than 95%, 85%, and 90%, respectively. These three types of cotton grafting method were not only available for the research of root-shoot communication, but also for the research of shoot-shoot and root-root signals exchange.