引进红树拉关木和两种乡土红树离子平衡及光合作用的比较研究

Comparison of ionic equilibrium and photosynthesis in introduced Laguncularia racemosa and two native mangrove species in China

关键词:  秋茄, 木榄, 拉关木, 离子平衡, 光合作用

Key words:  Kandelia obovata, Bruguiera gymnorrhiza, Laguncularia racemosa, ionic equilibrium, photosynthesis

摘要:

为了比较引进红树与乡土红树的耐盐性差异,该研究以引进红树植物拉关木(Laguncularia racemosa)和乡土红树植物木榄(Bruguiera gymnorrhiza)与秋茄(Kandelia obovata)幼苗作为实验材料,分析其在不同NaCl浓度(100、200、300、400 mmol·L^-1)处理下各器官离子浓度(Na⁺、Cl^–、K⁺、Ca²⁺和Mg²⁺)和叶光合作用的变化。结果表明:(1)高盐胁迫(400 mmol·L^-1 NaCl, 28 d)处理下,拉关木根系Na⁺增幅较小,秋茄根、叶Cl^–含量增幅均高于木榄和拉关木,说明拉关木在较高的盐浓度时能限制根系对Na⁺、Cl^–的吸收,减少向地上部分运输。(2)高盐胁迫均增加3种红树根、叶的K⁺浓度(木榄叶K⁺略有降低,差异不显著),表明3种红树均可吸收K⁺,来限制Na⁺对植物的伤害; 同时,降低3种红树根Ca²⁺浓度,但拉关木根Ca²⁺下降幅度小于秋茄和木榄,说明拉关木具有更强的防止Ca²⁺流失的能力。(3)拉关木根维持Na⁺/K⁺、Na⁺/Ca²⁺平衡的能力强于秋茄和木榄。(4)高盐胁迫引起秋茄与木榄光合速率均降低,而拉关木光合速率却增加了54.1%。综上所述,拉关木能限制根系对NaCl的吸收,有效维持Na⁺/K⁺、Na⁺/Ca²⁺的平衡,并保持较高的光合速率,这表明拉关木与木榄和秋茄相比具有更高的耐盐性。

Abstract:

To compare the salt resistance difference of the introduced mangrove and the native mangrove, dynamic variation of accumulation of Na⁺, Cl^–, K⁺, Ca²⁺ and Mg²⁺ in different tissues and photosynthesis were examined in 3-month-old seedlings of the introduced mangrove Laguncularia racemosa and two native species Bruguiera gymnorrhiza and Kandelia obovata under different treatments of NaCl(100, 200, 300 and 400 mmol·L^-1). The results were as follows:(1)The increase in Na⁺ concentration in Kandelia obovata and Bruguiera gymnorrhiza roots was greater than Laguncularia racemosa, while the concentration of Cl^– in Kandelia obovata was higher than that of the other two species in leaves and roots. Thus, Laguncularia racemosa could restrict root absorption of Na⁺, Cl^– and reduce transportation to aerial parts under salt stress of 400 mmol·L^-1.(2)K⁺ concentration in roots and leaves increased in seedlings of all the three mangrove species under high salt stress except that K⁺ concentration in Bruguiera gymnorrhiza leaves non-significantly reduced. The results showed that all the three mangrove species could absorb K⁺ to restrict the damage from Na⁺. The Ca²⁺ concentration decreased in all the three mangrove species under high salt stress, but the decrease in Ca²⁺ concentration in Laguncularia racemosa leave was less than that in Kandelia obovata and Bruguiera gymnorrhiza, indicating that Laguncularia racemosa had stronger ability to prevent the loss of Ca²⁺.(3) Laguncularia racemosa had a greater ability in maintaining Na⁺/K⁺ as well as Na⁺/Ca²⁺ than Kandelia obovata and Bruguiera gymnorrhiza.(4)The net photosynthetic rates of Kandelia obovata and Bruguiera gymnorrhiza under high salt stress reduced while that of the Laguncularia racemosa increased by 54.1%. Taken together, Laguncularia racemosa could restrict root absorption of NaCl, maintain effective Na⁺/K⁺, Na⁺/Ca²⁺, maintaining high net photosynthetic rate. The results indicated that Laguncularia racemosa had higher salt tolerance than Kandelia obovata and Bruguiera gymnorrhiza.