Plant Physiology

O'Toole, John C.; Crookston, R. Kent; Treharne, Kenneth J.; Ozbun, Jim L.

doi: 10.1104/pp.57.4.465pmid: 16659506

Abstract The response of several leaf gas exchange parameters were monitored with decreasing leaf water potential in Phaseolus vulgaris L. leaflets. These included photosynthesis, transpiration, CO2 compensation point, ribulose 1,5-diphosphate carboxylase activity, boundary layer plus stomatal, and mesophyll resistance to diffusion of CO2. Mesophyll resistance was calculated under two assumptions: (a) the CO2 concentration at the chloroplast was zero, and (b) it was equal to the CO2 compensation point. Contrary to some reports on bean, the estimates of mesophyll resistance (both models) increased with decreasing leaf water potential. Concurrently, the CO2 compensation point increased and ribulose 1,5-diphosphate carboxylase activity decreased as internal water stress increased. It is suggested that the mesophyll resistance term has been too liberally interpreted in the past and that future use be verified by an indicator of biochemical response to environmental stress such as the assay for ribulose 1,5-diphosphate carboxylase activity. 1 Present address: International Rice Research Institute, P. O. Box 933, Manila, Philippines. 2 Present address: Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul, Minn. 55108. 3 Present address: International Institute for Tropical Agriculture, Ibadan, Nigeria. This content is only available as a PDF. © 1976 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)

Pomeroy, M. Keith

doi: 10.1104/pp.57.4.469pmid: 16659507

Abstract A comparison of mitochondria isolated from 2 and 24 C grown winter wheat (Triticum aestivum L.) and winter rye (Secale cereale L.) seedlings revealed no correlation between changes in swelling and contraction characteristics and extent of cold hardiness. The swelling response changed markedly due to growth at low temperature, but the change was similar for the four cultivars examined. The swelling response was also observed to change rapidly during aging of isolated mitochondria, either at 2 or 24 C. Spontaneously swollen mitochondria, isolated from 24 C grown seedlings, contracted abruptly upon addition of certain oxidizable substrates, but this response was lost when seedlings were transferred from 24 to 2 C. Studies on the effect of various substrates and respiratory inhibitors on the swelling and contraction responses indicate that inhibitors which reduce or stop electron flow through the electron transport chain also inhibit substrate induced mitochondrial contraction. 1 Contribution No. 869 of Chemistry and Biology Research Institute, Agriculture Canada. This content is only available as a PDF. © 1976 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)

Alvim, Ronald; Hewett, Errol W.; Saunders, Peter F.

doi: 10.1104/pp.57.4.474pmid: 16659508

Abstract Changes in levels of abscisic acid (ABA) and cytokinin activity in the xylem sap of willow (Salix viminalis, L.) were followed throughout two growth cycles. Growth in spring was preceded by decreasing levels of ABA and an increase in cytokinin activity. The onset of dormancy was associated with low levels of cytokinins and high contents of ABA. A second peak of ABA was found in July which was not related to the dry weight of the sap. The main cytokinin activity in the sap was due to a zeatin riboside-like compound. 2 Present address: Centro de Pesquisas do Cacau, Caixa Postal 7, Itabuna, Bahia, Brasil. 1 This paper represents part of the Ph.D. dissertation of R.A., whose work was supported by the Conselho Nacional de Pesquisas (Brazil) and by the Ministry of Overseas Development (Great Britain). This content is only available as a PDF. © 1976 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)

Terry, Norman

doi: 10.1104/pp.57.4.477pmid: 16659509

Abstract Effects of sulfur on photosynthesis in sugar beets (Beta vulgaris L. cv. F58-554H1) were studied by inducing sulfur deficiency and determining changes in the photosynthesis of whole attached leaves and of isolated chloroplasts. The rates of photosynthetic CO2 uptake by intact leaves, photoreduction of ferricyanide, cyclic and noncyclic photophosphorylation of isolated chloroplasts, and the rate of CO2 assimilation by ribulose diphosphate carboxylase, decreased with decrease in total leaf sulfur from 2500 to about 500 μg g−1 dry weight. Sulfur deficiency reduced photosynthesis through an effect on chlorophyll content, which decreased linearly with leaf sulfur, and by decreasing the rate of photosynthesis per unit chlorophyll. There was only a small effect of sulfur deficiency on stomatal diffusion resistance to CO2 until leaf sulfur decreased below 1000 μg g−1 when stomatal resistance became a more significant proportion of the total diffusion resistance to CO2. Light respiration rates were positively correlated with photosynthesis rates and dark respiration was unchanged as leaf sulfur concentrations declined. 1 This work was supported by the Beet Sugar Development Foundation. This content is only available as a PDF. © 1976 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)

Mingo-Castel, Angel M.; Smith, Orrin E.; Kumamoto, Junji

doi: 10.1104/pp.57.4.480pmid: 16659510

Abstract Ethylene inhibited the tuberization of etiolated potato (Solanum tuberosum L. var. Red La Soda) sprout sections cultured in vitro. Carbon dioxide did not overcome the C2H4 inhibition but it was required for normal tuberization. Ethylene totally prevented root formation and development. It inhibited stolon elongation, and caused thickening and diageotropical growth of the stolon. In addition, C2H4 prevented the accumulation of both starch and red anthocyanin which are always present in a tuber. Ethylene also inhibited the kinetin-increased tuberization of sprout sections. Three to five days of exposure to CO2 were required to obtain promotion of tuberization of stolons cultured in vitro. Bicarbonate ion did not affect starch synthetase activity isolated from potato tubers in vitro. The evidence presented suggests that CO2 gas rather than HCO−3 or CO2−3 ions in equilibrium with dissolved CO2 was probably responsible for the stimulation. Morphological changes elicited by CO2 and C2H4 are described and the mechanism of action of both on tuberization is discussed. 2 Present address: Department of Horticulture, Washington State University, Pullman, Wash. 99163. 1 This paper represents part of the Ph.D. dissertation of A. M. Mingo-Castel. This content is only available as a PDF. © 1976 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)

Magyarosy, Andrew C.; Schürmann, Peter; Buchanan, Bob B.

doi: 10.1104/pp.57.4.486pmid: 16659511

Abstract Chloroplasts isolated from powdery mildew-infected (Erysiphe polygoni DC) sugar beet leaves (Beta vulgaris L) showed a reduction in the rate of electron transport and in the accompanying ATP formation in noncyclic photophosphorylation (water as electron donor, NADP as electron acceptor) and little or no change in the rate of ATP formation in cyclic photophosphorylation catalyzed by phenazine methosulfate. The inhibition of noncyclic photophosphorylation appeared to lead in the parent leaves to a decreased rate of photosynthetic CO2 assimilation and a shift in products resulting in a relative increase of amino acids. These changes were accompanied by alterations in chloroplast ultrastructure and by a reduction in the activity of enzymes necessary for the formation of organic acids (phosphoenolpyruvate carboxylase and malate dehydrogenase). These results are similar to the findings of Montalbini and Buchanan (1974 Physiol. Plant Pathol. 4: 191-196) with chloroplasts from rust-infected Vicia faba leaves. 2 On leave from the Laboratoire de Physiologie vegetale et Biochimie, Universite de Neuchatel, Switzerland. 1 This investigation was supported in part by Hatch and California Statewide Critical Applied Research Funds. This content is only available as a PDF. © 1976 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)

Shulman, Yaiv; Lavee, Shimon

doi: 10.1104/pp.57.4.490pmid: 16659512

Abstract Cytokinin activity was found in mature black olive fruits while in green fruits the activity was markedly lower. The substances with cytokinin activity showed chromatographic properties similar to those of nucleotides. Acid hydrolysis caused a shift of the active zone in the organic phase of 1-butanol-acetic acid-water (4:1:5) from RF 0.1 to RF 0.8. The possible relation of these endogenously appearing cytokinins to anthocyanin accumulation and aging of the fruit is discussed. 1 Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. 1975. No. 124-E. This content is only available as a PDF. © 1976 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)

Rosenthal, Gerald A.; Gulati, Dushyant K.; Sabharwal, P. S.

doi: 10.1104/pp.57.4.493pmid: 16659513

Abstract Growth studies with Lemna minor revealed the additive and synergistic growth-inhibiting properties of the canaline-urea cycle amino acids. Simultaneous canavanine and canaline treatment caused an additive reduction in frond production. Ureidohomoserine interacted with canaline or canavanine to affect synergistically L. minor growth by enhancing individual canavanine or canaline toxicity and increasing the additive growth reduction caused by canavanine plus canaline. The ornithineurea cycle amino acids effectively counteracted both the additive and synergistic growth-inhibiting properties of the canaline-urea cycle compounds. 1 This investigation was supported by grants to G.A.R. from the National Science Foundation (GB-40198), the National Institutes of Health (AM-17322), and the Research Committee of the University of Kentucky. 2 This paper is the second in a series on the biological effects of the canaline-urea cycle amino acids on higher plants. The first paper appeared in Plant Physiology 56: 420-424. This content is only available as a PDF. © 1976 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)

Cattolico, Rose Ann; Boothroyd, John C.; Gibbs, Sarah P.

doi: 10.1104/pp.57.4.497pmid: 16659514

Abstract Olisthodiscus luteus is a unicellular biflagellate alga which contains many small discoidal chloroplasts. This naturally wall-less organism can be axenically maintained on a defined nonprecipitating artificial seawater medium. Sufficient light, the presence of bicarbonate, minimum mechanical turbulence, and the addition of vitamin B12 to the culture medium are important factors in the maintenance of a good growth response. Cells can be induced to divide synchronously when subject to a 12-hour light/12-hour dark cycle. The chronology of cell division, DNA synthesis, and plastid replication has been studied during this synchronous growth cycle. Cell division begins at hour 4 in the dark and terminates at hour 3 in the light, whereas DNA synthesis initiates 3 hours prior to cell division and terminates at hour 10 in the dark. Synchronous replication of the cell's numerous chloroplasts begins at hour 10 in the light and terminates almost 8 hours before cell division is completed. The average number of chloroplasts found in an exponentially growing synchronous culture is rather stringently maintained at 20 to 21 plastids per cell, although a large variability in plastid complement (4-50) is observed within individual cells of the population. A change in the physiological condition of an Olisthodiscus cell may cause an alteration of this chloroplast complement. For example, during the linear growth period, chloroplast number is reduced to 14 plastids per cell. In addition, when Olisthodiscus cells are grown in medium lacking vitamin B12, plastid replication continues in the absence of cell division thereby increasing the cell's plastid complement significantly. 2 Present address: Botany Department, University of Washington, Seattle, Wash. 98195. 3 Present address: Department of Molecular Biology, University of Edinburgh, Edinburgh, Scotland. 1 Research was supported by the National Research Council of Canada (Grant A-2921) and the Quebec Department of Education. This content is only available as a PDF. © 1976 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)

Puech, Antoine A.; Rebeiz, Constantin A.; Crane, Julian C.

doi: 10.1104/pp.57.4.504pmid: 16659515

Abstract The application of (2-chloroethyl)phosphonic acid (Ethephon) to `Mission' fig fruits (Ficus carica L.) during late period II of their development stimulated ripening and change in color from green to bluish black within 8 days. Chlorophylls a and b decreased rapidly within 4 days after Ethephon treatment, and degradation continued at a decreasing rate for an additional 4 days, at which time the fruits had attained their maximum diameter and were considered fully ripe. Levels of β-carotene, lutein, violaxanthin, and neoxanthin decreased in a pattern similar to that of chlorophylls a and b. The rates of β-carotene and lutein degradation were initially greater than those of the xanthophyll pigments. Degradation rates of the various carotenoids were comparable 4 to 8 days after treatment. There was no measurable anthocyanin synthesis during a 2- to 4-day period following Ethephon treatment. Beyond this lag phase, anthocyanin accumulation was linear, and the amount of pigment synthesized was a function of both light intensity and duration. Although Ethephon promoted the rate of anthocyanin accumulation, it did not increase the total amount of pigment synthesized in treated fruits. Etiolation of fruits from the time of Ethephon treatment until maturity stimulated an increase in growth and completely inhibited anthocyanin production in the skin. Ethephon-treated fruits which ripened while etiolated were larger in diameter and higher in both fresh and dry weights than nonetiolated controls. 1 Present address: University of Illinois, Urbana, Ill. 61801. This content is only available as a PDF. © 1976 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)