Dua A, Talwar G, Singh R
Department of Chemistry and Biochemistry, Haryana Agricultural University, Hisar, India.
Indian J Biochem Biophys. 1994 Jun;31(3):171-6.
Rate of photosynthesis; primary photochemical reactions, viz. whole chain electron transport, PSI and PSII activities; polypeptide profiles and lipid composition of thylakoid membranes were determined at different stages of Brassica pod development. Net CO2 exchange rate increased till 20 days after anthesis (DAA), remained constant till 30 DAA and decreased thereafter. While stomatal conductance followed a similar pattern, transpiration rate and internal CO2 concentration were least affected by age. Chlorophyll content decreased from 10 DAA till maturity, However, Chl a:b ratio increased during the period of active photosynthesis and was maximum at 30 DAA. Among the photochemical activities, PSII activity was reduced to 30% in mature pods. Qualitatively, the polypeptide composition of PSI, PSII and their light harvesting complexes were not affected adversely by aging. Total lipids, phospholipids, glycolipids and total free fatty acids decreased with maturity. However, the decrease in glycolipid content was more severe particularly during maturity phase. It seems that decrease in glycolipid content of thylakoids and chlorophyll content of chloroplasts are responsible for the decrease in photochemical activity and hence a reduction in CO2 assimilation at later stages of pod development.
在甘蓝型油菜荚果发育的不同阶段，测定了光合作用速率、初级光化学反应，即整个链电子传递、PSI和PSII活性、类囊体膜的多肽谱和脂质组成。净二氧化碳交换率在开花后20天（DAA）之前增加，在30 DAA之前保持恒定，此后下降。虽然气孔导度遵循类似模式，但蒸腾速率和胞内二氧化碳浓度受荚果发育阶段的影响最小。叶绿素含量从10 DAA到成熟逐渐降低，然而，在光合作用活跃期，叶绿素a:b比值增加，并在30 DAA时达到最大值。在光化学活性中，成熟荚果中的PSII活性降低到30%。定性地说，PSI、PSII及其捕光复合体的多肽组成不受衰老的不利影响。总脂质、磷脂、糖脂和总游离脂肪酸含量随着成熟而降低。然而，糖脂含量的下降更为严重，尤其是在成熟阶段。类囊体糖脂含量的降低和叶绿体叶绿素含量的降低似乎是导致光化学活性下降的原因，从而导致荚果发育后期二氧化碳同化作用的降低。
