Showing papers in "Plant and Cell Physiology in 1982"

Inactivation of Photosynthetic Oxygen Evolution and Concomitant Release of Three Polypeptides in the Photosystem II Particles of Spinach Chloroplasts

Abstract: Photosystem II particles having an oxygen evolution activity as high as 300,ulnol mg-1 chlorophyll hr -1 were prepared from spinach chloroplasts using Triton X-IOO. The oxygen evolution system in these particles was stable; 70% of the original activity remained after storage of the particles at O°C for 7 days. When the particles were treated at pH 9.3, the oxygen evolution was specifically inactivated and three polypeptides having apparent molecular weights of 32,000, 24,000 and 15,000 were simultaneously released. This observation suggests that these polypeptides are associated with the oxygen evolution system of photosynthesis.

Compositions and Positional Distributions of Fatty Acids in Phospholipids from Leaves of Chilling-Sensitive and Chilling-Resistant Plants :

Abstract: The compositions and positional distributions of fatty acids in the major leafphospholipids of phosphatidylg lycerol, phosphatidylcholine and phosphatidylethanolamine were analyzed by gas-liquid chromatography and enzymic hydrolysis, and chilling-sensitive and chilling-resistant plants were compared with respect to the relative contents of palmitic and (ranj-jd3-hexadecenoic acids in the separated phospholipids. A distinct difference between these plants was found in the fatty acid compositions of phosphatidylglycerol, in which the sum of palmitic and trans-A 3-hexadecenoic acids ranged from 60 to 78% of the total fatty acids in 8 species of chilling-sensitive plants, and from 50 to 57% in 11 species of chilling-resistant plants. The only exception among the chillingsensitive plants in this respect was the tomato, in which the sum of palmitic and trans^]3-hexadecenoic acids in phosphatidylglycerol amounted to 54%. The fatty acid compositions and the positional distributions of fatty acids in phosphatidylg lycerol suggest that the occurrence of high proportions of dipalmitoyl and l-palmitoyl-2-((raRi-/J3hexadecenoyl) species in this lipid is correlated with the susceptibility to chilling of the leaves of higher plants. In the compositions and positional distributions of fatty acids in phosphatidylcholine and phosphatidylethanolamine, no difference was found between the chilling-sensitive and chilling-resistant plants.

Effect of Temperature on Starch Degradation in Chlorella vulgaris 11h Cells

Abstract: Analysis of products formed in Chlorella vulgaris l l h cells during photosynthesis in air containing 3,000 ppm CC>2 at various temperatures revealed that the level of Cstarch was maximum around 20—24°C and decreased with further rise in temperature until 40°C, while C-sucrose greatly increased at temperatures above about 28°C. Elevating the temperature from 20 to 38°C during photosynthetic CO2 fixation resulted in a remarkable decrease in C in starch and a concomitant increase in C in sucrose. This conversion of starch to sucrose when shifting the temperature from 20 to 38°C proceeded even in the dark. Hydrolysis of sucrose by /?-fructosidase showed that, irrespective of the experimental conditions, the radioactivities in sucrose were equally distributed between glucose and fructose. The enhancement of starch degradation with temperature rise was more remarkable than that of the activity of ribulose bisphosphate carboxylase from the same cells. When Chlorella cells which had been preloaded with C-starch after photosynthesis for 30 min at 20°C were incubated in the dark for an additional 30 min at 20°C, C-starch was degraded by only about 4%. However, the values after 30-min dark incubation at 28, 32, 36 and 40°C were increased by about 10, 19, 36 and 50%, respectively. During the temperature-dependent conversion of starch to sucrose, no significant amount of radioactivity accumulated in free glucose and maltose.