【摘要】 一、阳生植物（菠莱）叶绿体的 DCIP光还原活性显著高于阴生植物（吊兰、一叶兰）。Mg⁺⁺离子对此三种叶绿体的CDIP光还原活性都有促进,而且对阴生植物促进得更显著些。 二、在饱和强度激发光下,Mg⁺⁺离子对菠莱和一叶兰叶绿体DCIP光还原活性的促进,都比弱光下多。在限制速率激发光下,Mg⁺⁺离子对阴生植物的促进,比阳生植物更显著。 三、Mg⁺⁺离子对菠莱、一叶兰、吊兰叶绿体表观吸收光谱的影响是类似的。Mg⁺⁺离子使光谱显著变平。 四、比较了吸收光谱和差异光谱。Mg⁺⁺离子引起吸收降低最大的位置,不在峰上,而略有蓝移（3nm左右）。 五、观察了Mg⁺⁺离子对菠菜叶绿体表观吸收影响的动态过程。峰和肩处的吸收随时间逐渐下降,在吸收小的波段,最初几分钟内吸收上升,以后逐渐下降,甚至低于对照。 六、在菠莱叶绿体老化过程中,Mg⁺⁺离子对表现吸收光谱的影响,随着时间的延长（如一昼夜）而减少,而对DCIP光还原活性的促进,不但不减小,反而加强了。 七、我们的结论是:Mg⁺⁺离子促进了阳生植物和阴生植物叶绿体与PSⅡ有关反应（DCIP光还原反应）的活性,诱导了这些叶绿体结构的变化。更多还原

【Abstract】 1. It was observed that the DCIP photoreduction activity in chloroplasts ofspinach （a sun plant） was much higher than that of the shade plants. Mg⁺⁺ ion sti-mulated this activity of all these chloroplasts, and the stimulating action was moresignificant in the chloroplasts of the shade plants. 2. The effect of actinic light intensity upon the stimulating action of Mg⁺⁺ion on DCIP photoreduction activity in chloroplasts of spinach and Malaxis mono-phyllos was observed. The effect was more pronounced under saturated intensitythan that of rate-limiting intensity. Under rate-limiting intensity, the stimulatingaction of Mg⁺⁺ ion on the photoreduction activity of the shade plant was more pro-nounced. 3. The effect of Mg⁺⁺ ion on the apparent absorption spectrum of spinach andshade plant chloroplasts was observed. The changes were similar in these threechloroplasts. Mg⁺⁺ ion caused the apparent absorption spectrum to flattened out. 4. Comparing tbe apparent absorption spectrum with the (control minusMg⁺⁺) difference spectrum, we observed that the sites of maximum diminution cau-sed by Mg⁺⁺ ion were not on the peaks but shorter than the peaks about 3 nm. 5. The kinetics of the effect of Mg⁺⁺ ion on the apparent absorption.spectrumin spinach chloroplasts was observed. Within the duration （2.5 hours） of theexperiment, the absorption peaks and the shoulder fell with time; in the wavelengthregion of minimun absorption, the value of O.D. rose at first, then fell to a levelsometimes below the control. 6. The effects of Mg⁺⁺ ion on the apparent absorption spectrum and the DCIPphotoreduction activity of aged spinach chloroplasts were observed. Within theduration （24 hours） of the experiment, the effect on apparent absorption spectrumdiminished with time. The DCIP photoreduction activity was not only undimi-nished by Mg⁺⁺ ion, but was significantly enhanced with time. 7. These experiments lead to the conclusion that Mg⁺⁺ ion enhances DCIPphotoreduction （Hill） activity of both sun- and shadeplant chloroplasts, and inducestructural changes in these. chloroplasts.更多还原