长期水陆周期性变化条件下香根草形态性状和生物量分配的可塑性

香根草是能够长期适应三峡水库消落带生境的少数物种之一。虽然国内对香根草的引种栽培和研究已有几十年的历史，但是对香根草在三峡库区消落带长期水陆周期性变化条件下的生态适应对策还知之甚少。为此，以2008年在三峡水库巫山段消落带建立的香根草引种栽培试验示范基地为研究平台，在2016年对海拔166—169 m、169—172 m和172—175 m区段的香根草的形态性状、生物量及其分配特征进行了研究。结果表明：(1)海拔166—169 m香根草的分蘖株数、平均株高、节间数量、节间长度、叶片数/分蘖株、叶片数/丛、叶片长等各指标值均低于海拔169—172 m和海拔172—175 m,海拔166—169 m与其它海拔区段的节间数量差异显著(P<0.05);(2)海拔166—169 m香根草的根系数量最少，但根系长度最长；(3)海拔166—169 m无节间的香根草株数最多，且与海拔172—175 m和海拔169—172 m差异显著(P<0.05);(4)不同海拔区段香根草的总生物量大小表现为海拔172—175 m>海拔169—172 m>海拔166—169 m,且海拔166—...

Plasticity in phenotype and biomass allocation of Vetiveria zizanioides under long-term alternate flooding and drying

Vetiveria zizanioides (hereafter vetiver) is one of the few species that survived in the water-level fluctuation zone of the Three Gorges Reservoir. Although the introduction, cultivation, and research of vetiver in China has a history of decades, little is known about the adaptive strategies of vetiver that under the conditions of long-term flooding and drying periodic changes. Therefore, the plasticity in phenotype and biomass allocation of vetiver planted in altitude zones of 166-169 m, 169-172 m and 172-175 m above sea level in the water-level fluctuation zone of the Wushan section of the Three Gorges Reservoir in 2008 were studied in 2016. The results showed that:(1) the morphological traits (e.g.,number of tillers, average plant height, number of internodes, length of internodes, number of leaves per tiller, number of leaves per bush and length of leaves) of vetiver in altitude zone of 166-169 m were all lower than those in altitude zones of 172-175 m and 169-172 m. The number of internodes in altitude zone of 166-169 m was significantly different (P<0.05) from those in other two altitude zones (169-172 m and 172-175 m). (2) Compared with other two altitude zones, the number of roots in altitude zone of 166-169 m was the least while the length of roots was the longest. (3) The number of tillers without internodes in altitude zone of 166-169 m was the most, and the difference was significant with those of other two altitude zones (P<0.05). (4) The total biomass of vetiver in altitude zone of 172-175 m was the largest, followed by 169-172 m and 166-169 m altitude zones, and the difference between 166-169 m and 172-175 m altitude zones was significant. The ratio of underground to aboveground biomass and stem to leaf biomass were the lowest in altitude zone of 166-169 m. (5) The biomass of leaves, living stems and withered stems in the upper part and the root biomass in different soil layers were the highest in altitude zone of 172-175 m, followed by altitude zones of 169-172 m and 166-169 m. There was no significant difference in soil physical and chemical properties in different altitude zones. The difference in morphological traits and biomass of vetiver in different altitude zones was mainly attributed to the impacts of periodic alternate flooding and drying. Reducing plant height, controlling plant component size, and reducing biomass were beneficial to reduce the energy consumption of vetiver grow in low altitude area during flooding. While reducing the number of roots and prolonging the length of roots were beneficial to enhance the adsorptive capacity of nutrients and water during drying. Additionally, the biomass of vetiver in the low altitude zone was allocated more to the aboveground parts, especially leaves, which was conducive to photosynthetic production and carbohydrate accumulation and could lay the material foundation and energy reserve for future rapid recovery and growth of vetiver. These adaptive strategies were important for long-term survival and growth of vetiver in the water-level fluctuation zone of the Three Gorges Reservoir.