三峡水库长期水淹条件下耐淹植物甜根子草的资源分配特征

为研究历经三峡水库长期水淹的驯化后,不同海拔高程之间相同种源的甜根子草的生物量分配特征是否发生改变,进而探讨该物种对水淹胁迫表现出的适应性进化特征,试验于2008年初选育相同种源的甜根子草同龄幼苗栽植于三峡水库消落区甜根子草种植试验示范区,并考察了2012年、2013年不同海拔高程甜根子草植株的形态和生物量特征。试验共设置3个海拔高程,即水淹高程168、172m和不受水淹对照高程176m。试验结果表明:(1)较低高程的甜根子草植株较矮小细弱,168m高程的甜根子草植株主茎长和主茎基径显著低于对照176m高程(P0.05);平均节间长度随高程的降低而缩短;与之相反,主茎长/主茎基径随高程的降低而增大。(2)甜根子草的叶片厚度、叶片长/叶片宽、叶片长/叶鞘长均随海拔高程的降低而减小;与之相反,比叶面积随高程的降低而增大。(3)水淹前,甜根子草近端成熟节间的质量密度随高程的降低而增大;水淹后,其地上存活茎段基部成熟节间的质量密度在各高程之间无显著差异(P0.05)。以上研究结果表明,甜根子草历经三峡水库长期水淹的驯化后,生物量分配特征在不同海拔高程之间发生了改变,表现出了相应的驯化特征。相较于高高程的甜根子草植株而言,低高程的植株生长缓慢,采取低株高下的高向生物量投资策略;对叶的物质投资大部分分配到叶面积的增加、叶鞘的伸长生长和叶片的直立生长上,以加强植株的光合生产。

Effects of long-term submergence on resource allocation of Saccharum spontaneum Linn. in Three Gorges reservoir

To reveal the biomass allocation response of Saccharum spontaneum Linn. at different elevations to long-term submergence in Three Gorges Reservoir, the adaptability of S. spontaneum to submergence was studied. Similar-sized seedlings of S. spontaneum with the same provenance were planted at different elevations in our study area located in the hydro-fluctuation zone of the Three Gorges reservoir region in 2008. The morphological traits and biomass of the plants were examined in 2012 and 2013. Three elevations (in the submerged area: 168 m and 172 m; non-submerged area: 176 m) were measured. The results showed that: (1) The plants at the lower elevation were shorter, and the length and basal diameter of stems at 168 m elevation were significantly lower than those at 176 m elevation (P < 0.05). The ratio of stem length to basal diameter significantly increased with decreasing elevation, while the average internode length decreased with decreasing elevation. (2) The leaf blade thickness, the ratio of leaf length to leaf width, and the ratio of leaf length to sheath length decreased with decreasing elevation, but specific leaf area increased with decreasing elevation. (3) The mass density in basal internodes showed no significant difference at different elevations after submergence (P > 0.05), although there was a significant increment with decreasing elevation before submergence. These results demonstrated that S. spontaneum could decrease the growth of seedlings, increase leaf area and sheath elongation, and increase the hyponastic growth of leaves to adapt to long-term submergence at different elevations. This suggests that the alteration of biomass allocation might be a survival strategy for S. spontaneum when exposed to long-term submergence.