Richard G. Stout

Heat- and acid-tolerance of a grass commonly found in geothermal areas within Yellowstone National Park

Surveys of geothermally-heated environments in Yellowstone National Park have revealed an exceptionally heat-resistant grass Dichanthelium lanuginosum. Individuals of this species were able to withstand rhizosphere temperatures ranging from 40 to 57°C. Long-term (July and August, 1996) rhizosphere temperature measurements at three sites confirmed that geothermal heat maintained high soil temperatures during the night. Plants grown in the lab from field-collected seed display significantly higher shoot fresh weight when grown at soil temperatures of 35–41°C vs. 23–27°C. Though there is no difference in root fresh weight of plants grown at these two temperature regimes, the roots from the warmer soils are significantly shorter and more highly branched compared with plants grown in the cooler soils. This species also displays acid tolerance both in the field, with rhizosphere pH<3, measured at several sites, and when grown in the lab. In response to increased temperature, individual D. lanuginosum plants, either grown in the lab or collected in the field, expressed a low molecular weight protein that cross-reacted with heat shock protein antibodies.

Antibodies to cell-surface antigens of plant protoplasts

Abstract Both mouse and rabbit polyclonal antibodies to plant cell-surface antigens were developed by immunization with cell membrane material from oat (Avena sativa L. cv. Garry) roots. We were able to quickly assess the activity of antisera by monitoring the degree of protoplast agglutination and by using an indirect immunofluorescence assay. Using polyclonal antibodies to cell-surface antigens, we have found that oat root protoplasts share common surface antigens with protoplasts from other plant tissues and species. From experiments with antisera treated with excess oat leaf or oat root protoplasts before our immunoassays, we have obtained evidence for the existence of organ-specific cell-surface antigens in higher plants.

Tonoplast ATPase proton pumps in wheat roots

Abstract A crude membrane preparation isolated from wheat (Triticum aestivum L. cv. Winalta) roots was separated by differential and sucrose density gradient centrifugation into three fractions which were analysed using sodium dodecyl sulfate- polyacrylamide gel electrophoresis (SDS-PAGE). One of these fractions is enriched in nitrate-sensitive ATP ase activity and contains nitrate-sensitive and vanadate-insensitive, ATP-dependent proton-translocating activity. This presumptive tonoplast(TP)-enriched fraction also contains a 68–70-kDa polypeptide which strongly cross-reacts with antiserum developed against an amino-terminus peptide of the 70-kDa subunit of the carrot (Daucus carota) L. vacuolar ATPase. We have also found that AlF 4 − (fluoroaluminate), a reputed G protein activator, strongly inhibits vanadate-sensitive ATPase activity, but has relatively little effect on the nitrate-sensitive ATPase activity in wheat root membranes.

63 – Plant Cell Physiology

Publisher Summary This chapter discusses the physiological aspects of plant cell. Plant cells and animal cells are connected evolutionarily, sharing a common ancestor, but separated by over half a billion years of evolution. Throughout the plants life, new cells are typically produced in localized regions of relatively high mitotic activity called meristems. Morphological and physiological specialization of plant cells occurs primarily through modifications of the cell wall and plastids. Consisting of cellulose microfibrils embedded in a polysaccharide and protein matrix, the cell wall of plants both supports and protects the protoplast. Cell walls provide a physical barrier to insects and microbial pathogens and also allow plants to take up water. Plant cell division cannot occur without the formation of a new cell wall, which also determines the morphology of the cell during growth and differentiation. The other important structures of the plant cell, such as endomembrane systems, vacuoles, lipid bodies, plastids, microbodies, glyoxysomes, peroxisomes, cytoskeleton, and plasmodesmata are discussed. The discussion on cell-to-cell communication in plants includes intercellular transport via plasmodesmata, plant hormones, defensive signals, and interactions between plants and other organisms. Plant cells maintain a substantial resting potential across their plasma membrane, mainly through electrogenic, proton-translocating ATPases. This primary active transport mechanism drives most of the other secondary transport systems in plasma membrane. Plants can perceive subtle changes in light quality and quantity through at least two different kinds of photoreceptors—phytochrome and a blue-light photoreceptor.

Plant Cell Physiology

Publisher Summary The cell wall, plastids, and the vacuole are the three main structural features that distinguish plant cells from animal cells. Consisting of cellulose microfibrils embedded in a polysaccharide and protein matrix, the cell wall of higher plants both supports and protects the protoplast. This chapter describes that chloroplasts serve as the photosynthetic organelles in green plant tissues, while other types of plastids function in carbohydrate storage and in reproduction. Most mature plant cells are characterized by a large central vacuole, which permits plant cells to enlarge to a greater degree than animal cells and serves as an intracellular storage area for metabolites, and for hydrolytic enzymes involved in the breakdown and recycling of cellular components. In contrast to these three structural features, plant and animal cell membrane and cytoskeletal systems display fundamental similarities. The chapter also discusses that plant cells use chemical signals to communicate with each other and with other organisms. Such molecules travel from cell to cell via plasmodesmata, small conduits through the cell walls of adjacent cells, which allow the passage of relatively small molecules. Plant cells maintain a substantial resting potential across their plasma membrane primarily through electrogenic and proton-translocating ATPases.