丛枝菌根真菌对西南岩溶地区干旱及干湿交替下金银花根系生长的影响

Effects of AM fungus on root growth of Lonicera japonica under alternate dry and wet conditions in karst regions of southwestern China

近年来我国西南岩溶地区干旱频发、干湿交替现象严重,植被生存环境恶劣,植被恢复困难,石漠化程度呈加剧之势。丛枝菌根真菌能与植物根系形成互惠共生关系,对植物生长发育及抗逆性有积极影响。研究表明,丛枝菌根真菌能够提高植物的抗旱性。然而,丛枝菌根真菌是否能够提高宿主植物对干湿交替等多变环境的耐受性,目前并没有见到相关报道。以西南岩溶地区适生植物金银花为研究对象,利用盆栽控制实验,采用3因素(接种、水分处理、干旱时间处理)随机区组设计,研究了接种丛枝菌根-摩西管柄囊霉对不同干旱及干湿交替条件下金银花根系形态参数及根系生物量的影响。结果表明:短时间的干旱促进了未接种真菌的金银花根系长度、根系表面积和根系体积等形态参数,根系生物量增加,且复水对植物有一定补偿作用;但长期干旱后植株根长、根表面积和根体积等所有根系形态参数均降低,根系生物量显著下降,即长期干旱对金银花的根系生长产生了严重的抑制作用,且复水补偿作用因干旱的严重抑制作用而丧失。短时间干旱降低了接种植株的根长、根表面积和根体积等根系生长参数,根系生物量不变;复水后接种植株仍然具有补偿生长作用,其原因可能与菌根泡囊结构有关。随着干旱处理时间的延长,接种植物的根系也受到伤害,复水补偿能力丧失。可见,菌根真菌促进了喀斯特干旱和干湿交替条件下金银花的根系生长,且在干旱条件下促进作用更加显著,但与干旱时间和干旱强度并没有交互作用。

It is difficult for plants to survive and grow under the increasing stress caused by alternate dry and wet conditions in the limestone area of southwestern China where the rocky desertification has been getting worse. Arbuscular mycorrhizal fungi （AMF） have positive effects on plant growth and can increase resistance of plants to environmental stresses like drought. However, it is unclear whether AM fungi stimulate the tolerance of host plants to alternate dry and wet cycles. In this study, we took Lonicera japonica, an important native species in the karst regions of southwestern China, as our experimental material, and manipulated three factors （inoculation, water treatment, drought treatment duration） in a randomized design, to test whether AM fungus infection increases the plant＇ s tolerance to drought and alternate drought and wet cycles. We assessed the responses of its root length, root surface area, root diameter, and root biomass allocation and distribution to these treatments. The results showed that short periods of drought increased the root length, root surface, root volume and root biomass of non-inoculatedL. japonica seedlings. Re-watering after a short drought had a positive effect on the growth of seedlings. However, under a longer drought period, all the morphological traits such as root length, root diameter, root surface area and root volume were decreased for non-inoculated seedlings, and root biomass allocation declined remarkably. Re-watering after a prolonged drought showed no positive effect on root growth of seedlings. A short drought decreased root length, root diameter, root surface area and root volume, but did not change the root biomass allocation of inoculated seedlings. Re-watering after a short drought maintained the positive effect on root growth of seedlings, possibly via the mycorrhizal vesicle structure. However, a prolonged drought caused severely negative effects on the inoculated seedlings and the compensatory growth effects vanished. The results indicated that AM fungi enhanced root growth of L. japonica seedlings both at drought and alternate drought and wet conditions in the karst area; however, this response was independent of water availability and drought duration.