Plant Physiology

Duke, Stanley H.; Schrader, Larry E.; Henson, Cynthia A.; Servaites, Jerome C.; Vogelzang, Robert D.; Pendleton, John W.

doi: 10.1104/pp.63.5.956pmid: 16660844

Abstract The influences of low root temperature on soybeans (Glycine max [L.] Merr. cv. Wells) were studied by germinating and maintaining plants at root temperatures of 13 and 20 C through maturity. At 42 days from the beginning of imbibition, 13 and 20 C plants were switched to 20 and 13 C, respectively. Plants were harvested after 63 days. Control plants (13 C) did not nodulate, whereas those switched to 20 C did and at harvest had C2H2 reduction rates of 0.2 micromoles per minute per plant. Rates of C2H2 reduction decreased rapidly in plants switched from 20 to 13 C; however, after 2 days, rates recovered to original levels (0.8 micromoles per minute per plant) and then began a slow decline until harvest. Arrhenius plots of C2H2 reduction by whole plants indicated a large increase in the energy of activation below the inflection at 15 C. Highest C2H2 reduction rates (1.6 micromoles per minute per plant) were at 58 days for the 20 C control. Root respiration rates followed much the same pattern as C2H2 reduction in the 20 C control and transferred plants. At harvest, roots from 13 C-treated plants had the highest activities for malate dehydrogenase, glutamate oxaloacetate transaminase, and phosphoenolpyruvate carboxylase. Roots from transferred plants had intermediate activities and those from the 20 C treatment the lowest activities. Newly formed nodules from plants switched from 13 to 20 C had much higher glutamate dehydrogenase than glutamine synthetase activity. Photosynthetic rates on a leaf area basis were about three times as high in the 20 C control as compared to 13 C control plants. Photosynthetic rates of plants switched from 20 to 13 C decreased to less than half the original rate within 2 days. Photosynthetic rates of plants switched from 13 to 20 C recovered to rates near those of the 20 C control plants within 2 weeks. All leaf enzymes assayed at harvest, with the exception of nitrate reductase, were highest in activity in the 20 C control plants. 2 Present address: Light and Plant Growth Laboratory, Plant Physiology Institute, SEA, USDA, Beltsville, Maryland 20705. 1 Research supported by the College of Agricultural and Life Sciences, University of Wisconsin-Madison, the National Soybean Crop Improvement Council, USDA-CSRS Grant 616-15-72, and the American Soybean Association Research Grant 75-ASARF-208-3. This content is only available as a PDF. © 1979 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Sparace, Salvatore A.; Moore, Thomas S.

doi: 10.1104/pp.63.5.963pmid: 16660845

Abstract Intact mitochondria from the endosperm of castor bean were isolated on linear sucrose gradients. These mitochondria were ruptured and the membranes separated on discontinuous sucrose gradients into outer membrane, intact inner membrane, and ruptured inner membrane fractions. Each membrane fraction was examined for its capacity to synthesize phosphatidylglycerol, CDP-diglyceride, phosphatidylcholine via methylation, and phosphatidic acid. The syntheses of phosphatidylglycerol, CDP-diglyceride, and phosphatidylcholine were localized exclusively in the inner mitochondrial membrane fractions while phosphatidic acid synthesis occurred in both the inner and outer mitochondrial membranes. 1 This investigation was supported by National Science Foundation Grants GB-42599 and PCM 76-11933. This content is only available as a PDF. © 1979 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Chang, Chong W.

doi: 10.1104/pp.63.5.973pmid: 16660846

Abstract During cotton leaf development, starch accumulation was characterized by an initial rise to a maximum at the second to the fourth leaf from the apex. Then, starch content progressively decreased with leaf age. Starch accumulation was inversely related to the ratio of amylopectin to amylose. Differences between leaves in this ratio resulted from variations in both amylose and amylopectin levels. Fluctuations in amylose levels were more extreme than those of amylopectin. During the diurnal cycle, amylopectin was accumulated more than amylose in both young and old leaves during the day. During the night, amylopectin was degraded more than amylose in young leaves and vice versa in older leaves. The rate of change of the amylopectin to amylose ratio during the day was consistently higher than that during the night. This content is only available as a PDF. © 1979 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)