Carol A. Peterson

Bio: Carol A. Peterson is an academic researcher from University of Waterloo. The author has contributed to research in topics: Endodermis & Exodermis. The author has an hindex of 44, co-authored 109 publications receiving 6788 citations. Previous affiliations of Carol A. Peterson include Agriculture and Agri-Food Canada & University of Western Ontario.

How does water get through roots

Abstract: uptake of water. On the contrary, at low rates of transpiration such as during the night or during stress conOn the basis of recent results with young primary ditions (drought, high salinity, nutrient deprivation), maize roots, a model is proposed for the movement of the apoplastic path will be less used and the hydraulic water across roots. It is shown how the complex, ‘com- resistance will be high. The role of water channels posite anatomical structure’ of roots results in a ‘com- (aquaporins) in the transcellular path is in the fine posite transport’ of both water and solutes. Parallel adjustment of water flow or in the regulation of uptake apoplastic, symplastic and transcellular pathways play in older, suberized parts of plant roots lacking a suban important role during the passage of water across stantial apoplastic component. The composite transthe different tissues. These are arranged in series port model explains how plants are designed to within the root cylinder (epidermis, exodermis, central optimize water uptake according to demands from the cortex, endodermis, pericycle stelar parenchyma, and shoot and how external factors may influence water tracheary elements). The contribution of these struc- passage across roots. tures to the root’s overall radial hydraulic resistance is examined. It is shown that as soon as early metaxy- Key words: Composite transport model, endodermis, exolem vessels mature, the axial (longitudinal) hydraulic dermis, hydraulic conductivity, reflection coefficient, root, resistance within the xylem is usually not rate-limiting. water, water channels. According to the model, there is a rapid exchange of water between parallel radial pathways because, in contrast to solutes such as nutrient ions, water per- Introduction meates cell membranes readily. The roles of apoplastic One of the essential functions of roots is to supply the barriers (Casparian bands and suberin lamellae) in the shoot with water from the soil. The process of water root’s endo- and exodermis are discussed. The model

Root Endodermis and Exodermis: Structure, Function, and Responses to the Environment

Abstract: Roots of virtually all vascular plants have an endodermis with a Casparian band, and the majority of angiosperm roots tested also have an exodermis with a Casparian band. Both the endodermis and exodermis may develop suberin lamellae and thick, tertiary walls. Each of these wall modifications has its own function(s). The endodermal Casparian band prevents the unimpeded movement of apoplastic substances into the stele and also prevents the backflow of ions that have moved into the stele symplastically and then were released into its apoplast. In roots with a mature exodermis, the barrier to apoplastic inflow of ions occurs near the root surface, but prevention of backflow of ions from the stele remains a function of the endodermis. The suberin lamellae protect against pathogen invasion and possibly root drying during times of stress. Tertiary walls of the endodermis and exodermis are believed to function in mechanical support of the root, but this idea remains to be tested. During stress, root growth rates decline, and the endodermis and exodermis develop closer to the root tip. In two cases, stress is known to induce the formation of an exodermis, and in several other cases to accelerate the development of both the exodermis and endodermis. The responses of the endodermis and exodermis to drought, exposure to moist air, flooding, salinity, ion deficiency, acidity, and mechanical impedance are discussed.

Efficient lipid staining in plant material with sudan red 7B or fluorol [correction of fluoral] yellow 088 in polyethylene glycol-glycerol.

Abstract: Polyethylene glycol (400) with 90% glycerol (aqueous) is introduced as an efficient solvent system for lipid stains. Various lipid-soluble dyes were dissolved in this solvent system and tested for their intensity, contrast, and specificity of staining of suberin lamellae in plant tissue. The stability (i.e., lack of precipitation) of the various staining solutions in the presence of fresh tissue was also tested. When dissolved in polyethylene glycol-glycerol, Sudan red 7B (fat red) was the best nonfluorescent stain and fluorol yellow 088 (solvent green 4) was an excellent fluorochrome. These two dyes formed stable staining solutions which efficiently stained lipids in fresh sections without forming precipitates. Estimations of the solubilities of these dyes in the solvent compared with their solubilities in lipids of various chemical types indicated that they should both be effective stains for lipids in general.

A berberine-aniline blue fluorescent staining procedure for suberin, lignin, and callose in plant tissue

Abstract: A fluorescent staining procedure to detect suberin, lignin and callose in plants has been developed. This procedure greatly improves on previous methods for visualizing Casparian bands in root exodermal and endodermal cells, and performs equally well on a variety of other plant tissues. Berberine was selected as the most suitable replacement forChelidonium majus root extract after comparing the staining properties of the extract with those of four of its constituent alkaloids. Aniline blue counterstaining efficiently quenched unwanted background fluorescence and nonspecific berberine staining, while providing a fluorochrome for callose. When used with multichambered holders which allow simultaneous processing of freehand sections, this efficient staining procedure facilitates morphological studies involving large numbers of samples.

Principles of plant nutrition

Abstract: 1. Plant Nutrients. 2. The Soil as a Plant Nutrient Medium. 3. Nutrient Uptake and Assimilation. 4. Plant Water Relationships. 5. Plant Growth and Crop Production. 6. Fertilizer Application. 7. Nitrogen. 8. Sulphur. 9. Phosphorus. 10. Potassium. 11. Calcium. 12. Magnesium. 13. Iron. 14. Manganese. 15. Zinc. 16. Copper. 17. Molybdenum. 18. Boron. 19. Further Elements of Importance. 20. Elements with More Toxic Effects. General Readings. References. Index.

Plant growth promoting rhizobacteria as biofertilizers

Abstract: Numerous species of soil bacteria which flourish in the rhizosphere of plants, but which may grow in, on, or around plant tissues, stimulate plant growth by a plethora of mechanisms. These bacteria are collectively known as PGPR (plant growth promoting rhizobacteria). The search for PGPR and investigation of their modes of action are increasing at a rapid pace as efforts are made to exploit them commercially as biofertilizers. After an initial clarification of the term biofertilizers and the nature of associations between PGPR and plants (i.e., endophytic versus rhizospheric), this review focuses on the known, the putative, and the speculative modes-of-action of PGPR. These modes of action include fixing N2, increasing the availability of nutrients in the rhizosphere, positively influencing root growth and morphology, and promoting other beneficial plant–microbe symbioses. The combination of these modes of actions in PGPR is also addressed, as well as the challenges facing the more widespread utilization of PGPR as biofertilizers.

Bacterial endophytes in agricultural crops

Abstract: Endophytic bacteria are ubiquitous in most plant species, residing latently or actively colonizing plant tissues locally as well as systemically Several definitions have been proposed for endophyt

Carbohydrate-modulated gene expression in plants.

Abstract: Plant gene responses to changing carbohydrate status can vary markedly Some genes are induced, some are repressed, and others are minimally affected As in microorganisms, sugar-sensitive plant genes are part of an ancient system of cellular adjustment to critical nutrient availability However, in multicellular plants, sugar-regulated expression also provides a mechanism for control of resource distribution among tissues and organs Carbohydrate depletion upregulates genes for photosynthesis, remobilization, and export, while decreasing mRNAs for storage and utilization Abundant sugar levels exert opposite effects through a combination of gene repression and induction Long-term changes in metabolic activity, resource partitioning, and plant form result Sensitivity of carbohydrate-responsive gene expression to environmental and developmental signals further enhances its potential to aid acclimation The review addresses the above from molecular to whole-plant levels and considers emerging models for sensing and transducing carbohydrate signals to responsive genes

Physiological processes limiting plant growth in saline soils: some dogmas and hypotheses

Abstract: Recent progress in improving the salt tolerance of cultivated plants has been slow. Physiologists have been unable to define single genes or even specific metabolic processes that molecular biologists could target, or pinpoint the part of the plant in which such genes for salt tolerance might be expressed. While the physiological might be expressed. While the physiological processes are undoubtedly complex, faster progress on unraveling mechanisms of salt tolerance might be made if there were more effort to test hypotheses rather than to accumulate data, and to integrate cellular and whole plant responses. This article argues that salts taken up by the plant do not directly control plant growth by affecting turgor, photosynthesis or the activity of any one enzyme. Rather, the build-up of salt in old leaves hasten their death, and the loss of these leaves affects the supply of assimilates or hormones to the growing regions and thereby affects growth.