水体溶氧影响陆生植物喜旱莲子草(Alternanthera philoxeroides)和牛鞭草(Hemarthria altissima)对完全水淹的耐受力

溶氧是水环境中一个重要的环境因子,为了探讨水中的溶氧含量水平是否会对陆生植物的耐淹能力造成影响,研究了陆生植物喜旱莲子草(Alternanthera philoxeroides)和牛鞭草(Hemarthria altissima)在遭受不同溶氧含量水体完全淹没后的生长表现、存活情况和非结构碳水化合物的变化。实验结果表明:(1)水体中的溶氧含量显著影响了处于完全水淹环境中的喜旱莲子草和牛鞭草的存活。受高溶氧水体完全水淹的喜旱莲子草和牛鞭草主茎的完好程度和存活叶的数量均显著高于遭受低溶氧水体完全水淹的喜旱莲子草和牛鞭草,喜旱莲子草和牛鞭草在高溶氧水体完全水淹后的生物量比低溶氧水体完全水淹后要高;(2)水体中的溶氧含量显著影响了处于完全水淹环境中的喜旱莲子草和牛鞭草的生长,受高溶氧水体完全水淹的喜旱莲子草主茎伸长生长和不定根生长显著强于受低溶氧水体完全水淹的喜旱莲子草,在不定根的生长上牛鞭草也具有同样的表现。(3)高溶氧水环境有利于减小被完全淹没的喜旱莲子草和牛鞭草的碳水化合物消耗,两种植物在受高溶氧完全水淹后体内具有的非结构性碳水化合物含量均比受低溶氧完全水淹后高。(4)喜旱莲子草比牛鞭草能更好地耐受完全水淹,当处于低溶氧完全水淹时表现得更为明显,本研究表明入侵物种喜旱莲子草比本地物种牛鞭草具有更强的环境适应能力和水淹耐受能力。

Dissolved oxygen in water affects the tolerance of two terrestrial plants,Alternanthera philoxeroides and Hemarthria altissima, to complete submergence

Flooding is detrimental to terrestrial plants, usually reducing growth and survival rate. The negative impact of flooding on terrestrial plants is mainly attributed to the low oxygen content in water environment, which may result in energy crisis for terrestrial plants. Slow diffusion and relatively low solubility of oxygen in water lead to low oxygen content in water. Terrestrial plants live in the aerial environment with plenty of oxygen and have a suit of adaptations to such environment. To date, few studies have investigated whether the growth and survival of terrestrial plants, when completely submerged, are affected by the content of dissolved oxygen in water. In this study, using Alternanthera philoxeroides and Hemarthria altissima as model organisms (an invasive and a native terrestrial plant species, respectively, in the Three Gorges reservoir area), we examined the growth, survival, and non-structural carbohydrates of these plants when subjected to complete submergence with high (6.73 mg/L) and low level of dissolved oxygen (0.69 mg/L) in water. The following results were found in this study:(1) The level of dissolved oxygen in water had a significant influence on the survival of A. philoxeroides and H. altissima subjected to complete submergence. After the 30-day submergence treatment, the number of plants with undamaged stems, the number of surviving leaves, and the total plant biomass were higher in A. philoxeroides and H. altissima submerged in water with high dissolved oxygen content than in plants submerged in water with low dissolved oxygen content. (2) The level of dissolved oxygen in water affected the growth of completely submerged A. philoxeroides and H. altissima. Thus, A. philoxeroides submerged in water with high dissolved oxygen content showed pronounced stem elongation and adventitious roots formation compared to plants submerged in water with low dissolved oxygen content. Similarly, H. altissima produced more adventitious roots when submerged in water with high dissolved oxygen content. (3) High dissolved oxygen content in water reduced the carbohydrate consumption in completely submerged A. philoxeroides and H. altissima. Plants from both species had higher content of non-structural carbohydrates when completely submerged for 30 days in water with high dissolved oxygen content than in water with low dissolved oxygen content. (4) A. philoxeroides was more tolerant to complete submergence than H. altissima, which was more apparent when the plants were submerged in water with high dissolved oxygen content. Our study showed that, compared to the native species H. altissima, the invasive species A. philoxeroides is better adapted to unfavorable environmental conditions and exhibits higher submergence tolerance.