低氮下外源海藻糖对烤烟叶绿素代谢及叶绿体发育的影响

Effects of exogenous trehalose on chlorophyll metabolism and chloroplast development under low nitrogen condition

【目的】研究低氮下外源海藻糖对烟草幼苗叶绿素代谢与叶绿体发育的影响,以期揭示海藻糖调控低氮下植物氮素代谢的作用机制,为提高植物氮素利用效率提供参考。【方法】采用盆栽法比较外源海藻糖对低氮处理和正常氮素水平(对照)烟草幼苗叶片叶绿素酶活性、叶绿素合成前体物质含量、叶绿素合成关键酶活性及叶绿体结构的影响。【结果】施加外源海藻糖对低氮下烟草幼苗叶片叶绿素酶活性无显著影响(P>0.05),但可增加叶绿素合成前体物质5-氨基酮戊酸(ALA)、胆色素原(PBG)、尿卟啉原(URO)、原卟啉(Proto)、镁原卟啉(Mg-Proto)和原叶绿素酸酯(Pchl)含量,提高叶绿素合成途径中关键催化酶5-氨基酮戊酸脱水酶(ALAD)和尿卟啉原Ⅲ合成酶(UROS)活性。低氮处理后叶绿体结构破坏严重,膜系统全部解体,但外源施加海藻糖可改善叶肉细胞叶绿体的完整性。【结论】在低氮环境下施加外源海藻糖能提高烤烟幼苗的叶绿素含量,其原因不在于海藻糖可抑制叶绿素的降解,而在于海藻糖能促进叶绿素的合成并维持叶绿体结构的完整性。

【Objective】This study was conducted to analyze the effects of exogenous trehalose on tobacco seedlings chlorophyll metabolism and chloroplast development under low nitrogen condition,to reveal the underlying mechanisms that trehalose regulated nitrogen metabolism under low nitrogen condition,and to provide reference for improving plants nitrogen use efficiency.【Method】Effects of exogenous trehalose on chlorophyllase activity,precursor substance of chlrophyll biosynthesis,chlorophyllase biosynthesis core enzyme activity and chloroplast structure of seedlings were investigated with a pot experiment simulating low nitrogen condition(treatment)and optimal condition(control).【Result】There was no significant effects on chlorophyllase activity when exogenous trehalose was applied to tobacco seedlings under low nitrogen condition(P>0.05),however,contents of precursor substances of chlorophyll biosynthesis including 5-aminolevulinic acid(ALA),porphobilinogen(PBG),urogen(URO),protoporphyrin(Proto),Mg-protoporphyrin(Mg-Proto)and protochlorophyllide(Pchl)were increased,and activities of key enzymes of chlorophyll biosynthesis such as 5-aminolevelinate dehydratase(ALAD)and uroporporphyrinogn Ⅲ synthase(UROS)were enhanced. The structure and membrane system of chloroplast was destroyed seriously after long time low nitrogen treatment. Applying of exogenous trehalose improved the integrity of mesophyll cell.【Conclusion】Instead of inhibiting chlorophyll degradation,the increased chlorophyll content in exogenous trehalose applied seedlings is due to its increased chlorophyll biosynthesis and the integrity of chloroplast under low nitrogen condition.