内蒙古高原西部荒漠区四种锦鸡儿属植物水力结构变化的比较研究

本文采用改良的冲洗法，比较了内蒙古高原西部荒漠区锦鸡儿属(Caragana) 4 种优势植物—柠条锦鸡儿（C. korshinsk）、狭叶锦鸡儿（C. stenophylla）、垫状锦鸡儿（C. tibetica）和荒漠锦鸡儿（C. roborovoskyi）的水力结构日变化和季节变化，目的是了解4种锦鸡儿属植物对荒漠区环境的适应性及其差异。研究发现：4种锦鸡儿属植物的比导率、叶比导率均为早晚高、中午低的单谷日变化曲线；三个季节相比较，夏季的比导率、叶比导率最大；胡伯尔值春季>夏季>秋季。三个季节比导水率日平均值、夏季和秋季的叶比导率、三个季节的胡伯尔值都表现为：柠条锦鸡儿>荒漠锦鸡儿>狭叶锦鸡儿>垫状锦鸡儿；三个季节比导水率日变幅和春季叶比导率表现为：柠条锦鸡儿>荒漠锦鸡儿>垫状锦鸡儿>狭叶锦鸡儿。4个种比导水率日平均值的季节变幅相似。这些结果表明：（1）荒漠区锦鸡儿属植物的水力结构限制了水分运输，使其避免了中午的高蒸腾。（2）荒漠区锦鸡儿属植物通过较高的水分运输效率及较好的叶供水效率适应夏季的高温和强辐射，维持水分平衡；锦鸡儿属植物胡伯尔值的季节变化保证了其在春、夏季快速生长期有较好的水分供应。（3）较高的比导率、叶比导率和胡伯尔值导致了柠条锦鸡儿良好的水分供应和高蒸腾速率，进而导致了柠条锦鸡儿较快的生长速度，这说明柠条锦鸡儿对荒漠环境的适应性好于其它三个种；柠条锦鸡儿的输水效率高，但易发生严重的空穴和栓塞。

Variation in hydraulic architecture of four Caragana species in the desert region on the Inner Mongolian Plateau

Caragana species are able to survive in the stressful climatic conditions (e.g. very limited precipitation, high temperature and strong solar radiation) within the desert region on the Inner Mongolian Plateau through ecological adaptations to the environment. In the desert region, precipitation has the most important influence on plant growth and development. In order to understand how Caragana species are adapted to the arid desert environment, we investigated daily and seasonal variation in the hydraulic architecture (specific conductivity, leaf specific conductivity and Huber value) of four dominant Caragana species (Caragana korshinskii, C. stenophylla, C. tibetica and C. roborovsky), which grow in the desert region on the Inner Mongolian Plateau. We examined the hydraulic architecture of these Caragana species using the improved flushing method. The results showed that there was significant daily and seasonal variation in the hydraulic architecture of the four Caragana species. For all four Caragana species, the specific conductivity and leaf specific conductivity were high in the morning and afternoon and low at noon, showing a curve with single valley. Specific conductivity and leaf specific conductivity were highest in the summer, while Huber values were highest in spring, lower in summer, and lowest in autumn. There was also significant interspecific variation in hydraulic architecture among the four Caragana species. For daily averages of specific conductivity in the three seasons, leaf specific conductivity in summer and autumn, and Huber value in the three seasons, our results followed the pattern : C. korshinski > C. roborovoskyi > C. tibetica > C. stenophylla. For diurnal variation extent of specific conductivity in the three seasons, and leaf specific conductivity in the spring, our results followed the pattern: C. korshinski > C. roborovoskyi > C. stenophylla > C. tibetica. Seasonal variation extent of the daily average of specific conductivity was similar among the four Caragana species. Based on our results, we drew the following conclusions: (1) The hydraulic architecture of the four desert Caragana species limited water transport, which might decrease transpiration at noon. (2) Caragana species might be adapted to high temperatures and strong solar radiation through high water transport efficiency and better water supply to leaves to maintain relatively stable water status. The seasonal variation in Huber values ensured better water supplies to the four Caragana species in the spring and summer, when these species grew relatively rapidly. (3) Among the four Caragana species, C. korshinskii had the highest specific conductivity, leaf specific conductivity and Huber values, resulting in better water supply and higher transpiration rates, and thereby faster growth rates, which suggests that C. korshinskii is better adapted to the desert environment than the other three Caragana species. However, although C. korshinskii had higher water transpiration efficiency, this species was more prone to having serious cavitation and embolism.