High respiratory activity of stomatal guard-cell protoplasts

High respiratory activity of guard-cell protoplasts from Vicia faba L.

by Shimazaki K.-i., Gotow K., Sakaki T., Kondo N. (1983)

Ken-ichiro Shimazaki, 1, Kiyoshi Gotow, 2, Takeshi Sakaki, 1, Noriaki Kondo, 1

1 Division of Environmental Biology, The National Institute for Environmental Studies, Yatabe, Ibaraki 305, Japan

2 Department of Pure and Applied Sciences, College of General Education,
University of Tokyo, Tokyo 153, Japan

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In Plant, Cell & Environment 24: 1049-1056 –  https://doi.org/10.1093/oxfordjournals.pcp.a076607 – 

https://academic.oup.com/pcp/article-abstract/24/6/1049/1858924?redirectedFrom=fulltex

Abstract

The rate of O₂ uptake was about 29 times higher in guard cell protoplasts (GCPs) than in mesophyll protoplasts (MGPs) on a Chi basis. The O₂ uptake was inhibited by respiratory inhibitors, but stimulated by respiratory uncouplers.

On a Chi basis, the activities of Cyt c oxidase and NADH-Cyt c reductase, mitochondrial enzymes, were about 27 and 35 times higher in GCPs than in MCPs. On a Chi basis, the ATP content was about 9 times higher in GCPs. The amount of ATP in GCPs was decreased by respiratory inhibitors, an energy transfer inhibitor, and uncouplers of oxidative phosphorylation. On a volume basis, GCPs had 8- to 10-fold higher respiratory activities than MCPs, but had a low Chi content and lacked the activity of NADP-glyceraldehyde-3-phosphate dehydrogenase (NADP-GAPD), the Calvin cycle enzyme.

From these results, we concluded that oxidative phosphorylation plays a main role in ATP production in guard cells and that guard cells have a heterotrophic feature.

Salicylhydroxamic acid (SHAM) in combination with KCN or NaN₃ strongly inhibited O₂ uptake, indicating the presence of cyanide-resistant respiration in guard cells. Phenylmercuric acetate (PMA), a potent inhibitor of stomatal opening, reduced the ATP content of GCPs by about 90%, whereas it had a relatively small effect on the ATP level of MCPs. The specific effect of PMA on GCPs is discussed.

Light‐induced alkalinization of the suspending medium of stomatal protoplasts

 

 

Light‐induced alkalinization of the suspending medium of guard cell protoplasts from Vicia faba

by Gotow K., Sakaki T., Kondo N., Kobayashi K., Syôno K (1985)

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in Plant Physiology 79: 825-828 – DOI: https://doi.org/10.1104/pp.79.3.825 –

http://www.plantphysiol.org/content/79/3/825

Abstract

The light-dependent pH changes in the suspending medium of guard cell protoplasts (GCP) from Vicia faba were studied.

Upon illumination, the medium was initially slightly alkalinized and then acidified. The extent of alkalinization was lower in CO₂-free air than in normal air. This initial alkalinization was inhibited by DCMU.

Acidification in CO₂-free air became observable in shorter duration of light exposure than that in normal air. The rate of acidification was higher in CO₂-free air than in normal air. The CO₂ level of the medium decreased in the light, and increased in the dark. ¹⁴CO₂uptake was enhanced 2- to 3-fold by light, but not in the presence of DCMU.

These results indicate that photosynthetic CO₂ fixation does take place in GCP and that the initial alkalinization is due to this photosynthetic CO₂ uptake. Diethylstilbestrol, a nonmitochondrial membrane-bound ATPase inhibitor, inhibited the acidification, suggesting that the acidification resulted from H⁺ extrusion by GCP.

The acidification in light was also prevented by KCN, and partly by DCMU. Possible mechanisms of alkalinization and acidification are discussed in relation to guard cell metabolism.

Lipids and fatty acids in stomata

 

 

Lipids and fatty acids in guard-cell protoplasts from Vicia faba leaves

by Sakaki T., Satoh A., Tanaka K., Omasa K., Shimazaki K.-I. (1995)

Takeshi Sakaki, ^∗ Atushi Satoh, ^∗ Kiyoshi Tanaka, ^‡ Kenji Omasa, ^‡ Ken-Ichiro Shimazaki, ^§

^a

Department of Bioscience and Technology, School of Engineering, Hokkaido Tokai University, Minami-ku, Sapporo 005, Japan

^b

Environmental Biology Division, The National Institute for Environmental Studies, Onogawa, Tsukuba 305, Japan

^c

Biological Laboratory, College of General Education, Kyushu University, Ropponmatsu, Fukuoka 810, Japan

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in Phytochemistry 40: 1065–1070 – DOI: 10.1016/0031-9422(95)00272-9 – 

https://www.sciencedirect.com/science/article/pii/0031942295002729

Abstract

Guard-cell and mesophyll-cell protoplasts were isolated from Vicia faba leaves, and their lipids and fatty acids quantitatively analysed.

All the glycerolipids and fatty acids that occurred in mesophyll-cell protoplasts were found in guard-cell protoplasts. On a total fatty acid basis, levels of chloroplast lipids (monogalactosyldiacylglycerol, digalactosyldiacylglycerol and sulphoquinovosyldiacylglycerol) and phosphatidylglycerol were lower and their constituent fatty acids were more saturated in guard-cell protoplasts than in mesophyll-cell ones.

In contrast, levels of extrachloroplastic lipids (phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol and cardiolipin) were higher in guard-cell protoplasts than in mesophyll-cell protoplasts.

These results suggest that extrachloroplastic membrane systems, including mitochondria, are more developed than chloroplast membranes. In addition, guard-cell protoplasts contained a large amount of triacylglycerols, a probable component of spherosomes, lipid droplets and/or plastoglobuli, which are frequently observed in guard cells.

High respiratory activity of stomata protoplasts

 

Photo credit: Google

Vicia faba

High respiratory activity of guard cell protoplasts from Vicia faba L.

by Shimazaki K.-I., Gotow K., Sakaki T., Kondo N. (1983)

Ken-ichiro Shimazaki

 

Kiyoshi Gotow

 

Takeshi Sakaki

 

Noriaki Kondo

in Plant Cell Physiol 24: 1049-1056 – DOI: https://doi.org/10.1093/oxfordjournals.pcp.a076607 –

Google Scholar –

https://academic.oup.com/pcp/article-abstract/24/6/1049/1858924

Abstract

The rate of O₂ uptake was about 29 times higher in guard cell protoplasts (GCPs) than in mesophyll protoplasts (MGPs) on a Chi basis. The O₂ uptake was inhibited by respiratory inhibitors, but stimulated by respiratory uncouplers.

On a Chi basis, the activities of Cyt c oxidase and NADH-Cyt c reductase, mitochondrial enzymes, were about 27 and 35 times higher in GCPs than in MCPs. On a Chi basis, the ATP content was about 9 times higher in GCPs. The amount of ATP in GCPs was decreased by respiratory inhibitors, an energy transfer inhibitor, and uncouplers of oxidative phosphorylation.

On a volume basis, GCPs had 8- to 10-fold higher respiratory activities than MCPs, but had a low Chi content and lacked the activity of NADP-glyceraldehyde-3-phosphate dehydrogenase (NADP-GAPD), the Calvin cycle enzyme.

From these results, we concluded that oxidative phosphorylation plays a main role in ATP production in guard cells and that guard cells have a heterotrophic feature.

Salicylhydroxamic acid (SHAM) in combination with KCN or NaN₃ strongly inhibited O₂uptake, indicating the presence of cyanide-resistant respiration in guard cells.

Phenylmercuric acetate (PMA), a potent inhibitor of stomatal opening, reduced the ATP content of GCPs by about 90%, whereas it had a relatively small effect on the ATP level of MCPs.

The specific effect of PMA on GCPs is discussed.