克隆水分整合有助胡杨无性系幼株在极端干旱生境下保持更高生存优势

Clonal water integration contributes to more survival advantages for Populus euphratica young ramets in the hyper-arid habitat

以塔里木河下游的胡杨为对象,研究胡杨母株与其克隆幼株间的克隆水分整合特征及对克隆幼株生理机能的影响.结果表明:胡杨母株与其克隆幼株间存在明显的以顶向传输为特征的水分整合,母株对克隆幼株的日平均水分整合流量为同区域长势相近的实生幼株通过自身根系日平均获取水量的3倍,克隆幼株因水分整合而能够获取与母株相似且较实生幼株水分来源相对较深层的土壤水,拥有更好的水分获取能力.这使胡杨克隆幼株较实生幼株保持显著更高的叶片水分含量,且黎明前和正午叶水势分别显著增加10.0%和29.7%.更好的水分生理状态使克隆幼株的光合电子传递速率与光适应下实际光化学效率显著高出实生幼株23.4%和11.5%,并能够保持显著更低的光系统Ⅱ过剩激能比例和光抑制风险.这可能让胡杨克隆幼株在极端干旱生境中较实生幼株保持更高的生存优势.

The proposed investigation was carried on the characteristics of clonal water integration between the Populus euphratica mother tree and its young ramets, as well as its effects on the phy- siological traits of young ramets at the lower reaches of Tarim River. The results showed that there was obvious water integration characterized by acropetal water transport between P. euphratica mother tree and its young ramets. The mean daily flow by water integration from the mother tree to its young ramets was three times as the seedlings with similar growth status at the same habitat by getting water by itself roots. Compared with the P. euphratica seedlings, the young ramets could take much more water from relatively deeper soil layers just like their mother tree. It indicated the young ramets maintained a better water acquisition ability due to clonal water integration. There was obviously higher leaf water content of young ramets than seedlings, and especially the water poten- tial in the predawn and midday was increased by 10.0% and 29.7%, respectively. The advantaged water status of young ramets made the photosystem II electron transport rate and actual photochemi- cal efficiency of photosystem II in light-adapted leaves increase by 23.4% and 11.5% than seed- lings, respectively, and also made the young ramets maintain a significantly lower excess excited energy in photosystem II and a lower risk of photoinhibition than seedlings. All of the above cha- racteristics would impel the P. euphratica young ramets had higher survival advantages than seed- lings at hyper-arid habitats.