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

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Na Cl浓度(100、200、300、400 mmol·L^(-1))处理下各器官离子浓度(Na^+、Cl~–、K^+、Ca^(2+)和Mg^(2+))和叶光合作用的变化。结果表明:(1)高盐胁迫(400 mmol·L^(-1)Na Cl,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Ca^(2+)浓度,但拉关木根Ca^(2+)下降幅度小于秋茄和木榄,说明拉关木具有更强的防止Ca^(2+)流失的能力。(3)拉关木根维持Na^+/K^+、Na^+/Ca^(2+)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Na Cl的吸收,有效维持Na^+/K^+、Na^+/Ca^(2+)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。

To compare the salt resistance difference of the introduced mangrove and the native mangrove,dynamic variation of accumulation of Na^＋,Cl^–,K^＋,Ca^2＋and Mg^2＋ in different tissues and photosynthesis were examined in 3-monthold seedlings of the introduced mangrove Laguncularia racemosa and two native species Bruguiera gymnorrhiza and Kandelia obovata under different treatments of Na Cl（ 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 Ca^2＋concentration decreased in all the three mangrove species under high salt stress,but the decrease in Ca^2＋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 Ca^2＋.（ 3） Laguncularia racemosa had a greater ability in maintaining Na^＋/ K^＋as well as Na^＋/ Ca^2＋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 Na Cl,maintain effective Na^＋/ K^＋,Na^＋/ Ca^2＋,maintaining high net photosynthetic rate. The results indicated that Laguncularia racemosa had higher salt tolerance than Kandelia obovata and Bruguiera gymnorrhiza.