Showing papers in "Plant and Cell Physiology in 1984"

Comparative photosynthetic properties of palisade tissue chloroplasts and spongy tissue chloroplasts of Camellia japonica L.: functional adjustment of the photosynthetic apparatus to light environment within a leaf

Abstract: Description d'une technique permettant d'isoler les deux categories de chloroplastes, et comparaison de leur teneur en chl a/b, de leur composition polypeptidique de leur spectre de fluorescence, de leur cinetique d'induction et de leur activite de transporteur d'electron

Variations in the Photosynthesis Rate and Activity of Photosynthetic Enzymes in Maize Leaf Tissue of Different Ages

Abstract: Highly good correlations for the extractable activities of ribulose-l,5-bisphosphatecarboxylase, pyruvate,Pj dikinase, phosphoenolpyruvate carboxylase, NADP-malatedehydrogenase and NADP-malic enzyme and the rate of photosynthesis were found inmaize leaves of various ages. The activities of the first two enzymes were similar to, orslightly higher than, the photosynthesis rate, whereas the activities of the other enzymeswere 2 to 6 times higher than the photosynthesis rate. These results suggest thatpyruvate,Pj dikinase and ribulose-l,5-bisphosphate carboxylase may be rate-limitingfactors in maize.Key words: C4 photosynthesis — Maize leaf — Pyruvate,Pj dikinase — RuBPcarboxylase — Zea mays.

Measurement of Stomatal Aperture by Digital Image Processing

Abstract: We developed a new digital image processing technique for exactly measuring the degree of stomatal opening, that is, the ratio of the width to the maximum length of a stomatal pore, and the pore area. We applied this technique to evaluate responses to SO2 of neighboring stomata in a small region of an intact attached leaf, with the following results: 1) The pore region could be exactly extracted even when the original digital image was of poor quality. The standard errors in the evaluation of the pore area, the pore length, and the pore width were 10 jum, 0.3 fim and 0.3 jim, respectively. 2) A wide variety of responses to SO2 was found among neighboring stomata in a small region of an attached leaf. The differences were especially remarkable before water-soaking and wilting. When these began, kj showed a local maximum value, and then all the stomata began to close. These results suggest that stomatal responses of intact growing plants to air pollutants should be examined from the standpoint of not only the average movement of many stomata but also the movement of each stoma and that the interrelationship among movements of neighboring stomata should be investigated to clarify the mechanism of stomatal responses to air pollutants.

Membrane Fluidity in Senescing Apples: Effects of Temperature and Calcium,,

Abstract: Mise en evidence de differences significatives des indices de polarisation de fluorescence du DPH (diphenyl-1,6-hexatriene-2,3,5) des membranes des microsomes de pommes selon qu'elles ont ete entreposees au froid (2 o C) ou a temperature ordinaire et traitees ou non prealablement par le calcium

Metabolism and Excretion of Caffeine during Germination of Coffea arabica L

Abstract: To investigate the physiological role of the purine alkaloids during germination, seeds of Coffea arabica were allowed to germinate under aseptic conditions on agar at 26°C, either in the dark or in the light. After imbibition for 7 days less than 1% of the seed caffeine is found in the agar, indicating a strong diffusion barrier at the surface of the coffee bean. After 56 days, when the radicle has grown deep into the agar support, a considerable amount (22%) of caffeine is excreted. The total caffeine content increases during germination for 56 days by 83% in the dark and by 51% in the light, whereas the soluble protein falls drastically. We propose that caffeine is not a nitrogen reserve for germination and acts against competitors (release into the soil) and against predators (concentration increase in the tissue)