Plant physiology

About: Plant physiology is a research topic. Over the lifetime, 1537 publications have been published within this topic receiving 72038 citations.

The physiology of spore germination in fungi

Abstract: The physiology of spore germination has interested mycologists since about the middle of the last century, and reports by the pioneer investigators usually included some observations on this subject (5, 7, 28, 41, 65, 67, 69, 70, 153, 154, 155, 158, 171). In 1860 Hoffman (70) published a paper devoted entirely to this field, and de Bary's great book on the morphology and development of fungi (28) contains much information that is still useful to physiologists. In fact, most of the phenomena that concern students today were investigated before the close of the 19th century. Certain new aspects have, of course, since then been investigated, such as enzyme systems and respiratory mechanisms; in addition more critical techniques have been applied in recent researches. Only two important reviews of the subject have been published, one by Duggar in 1901 (37) and the other by Doran in 1922 (32). Since most of the data on spore germination are ineluded in papers devoted primarily to either plant pathology or mildew prevention, the information has been difficult to collate ; and since comparatively few fungi have been studied, very few generalizations on spore germination are possible. Germination is the initial stage in the development of a fungus myeelium from its spore. It differs from the growth of hyphae primarily in the ability of the spore to utilize its stored reserves for metabolism and consequently in the capacity of many spores to germinate either in water or very simple media. Another difference is that germination need not be accompanied by synthesis of protein. Physiologically it is characterized by transformation of a spore from a stage of low to one of high metabolic activity (46, 52, 53, 54, 91, 92, 95), and morphologically by a swelling of the spore and production of a germ tube (28, 41, 51). The term \"germi-

Stress-related hormones and glycinebetaine interplay in protection of photosynthesis under abiotic stress conditions

Abstract: Plants subjected to abiotic stresses such as extreme high and low temperatures, drought or salinity, often exhibit decreased vegetative growth and reduced reproductive capabilities. This is often associated with decreased photosynthesis via an increase in photoinhibition, and accompanied by rapid changes in endogenous levels of stress-related hormones such as abscisic acid (ABA), salicylic acid (SA) and ethylene. However, certain plant species and/or genotypes exhibit greater tolerance to abiotic stress because they are capable of accumulating endogenous levels of the zwitterionic osmolyte-glycinebetaine (GB). The accumulation of GB via natural production, exogenous application or genetic engineering, enhances plant osmoregulation and thus increases abiotic stress tolerance. The final steps of GB biosynthesis occur in chloroplasts where GB has been shown to play a key role in increasing the protection of soluble stromal and lumenal enzymes, lipids and proteins, of the photosynthetic apparatus. In addition, we suggest that the stress-induced GB biosynthesis pathway may well serve as an additional or alternative biochemical sink, one which consumes excess photosynthesis-generated electrons, thus protecting photosynthetic apparatus from overreduction. Glycinebetaine biosynthesis in chloroplasts is up-regulated by increases in endogenous ABA or SA levels. In this review, we propose and discuss a model describing the close interaction and synergistic physiological effects of GB and ABA in the process of cold acclimation of higher plants.

Effects of increased atmospheric CO2 and N supply on photosynthesis, growth and cell composition of the cyanobacterium Spirulina platensis (Arthrospira)

Abstract: The consequences of the addition of CO2 (1%) in cultures of S. platensis are examined in terms of biomass yield, cell composition and external medium composition. CO2 enrichment was tested under nitrogen saturating and nitrogen limiting conditions. Increasing CO2 levels did not cause any change in maximum growth rate while it decreased maximum biomass yield. Protein and pigments were decreased and carbohydrate increased by high CO2, but the capability to store carbohydrates was saturated. C:N ratio remained unchanged while organic carbon released to the external medium was enhanced, suggesting that organic carbon release in S. platensis is an efficient mechanism for the maintenance of the metabolic integrity, balancing the cell C:N ratio in response to environmental CO2 changes. CO2 affected the pigment content: Phycocyanin, chlorophyll and carotenoids were reduced in around 50%, but the photosynthetic parameters were slightly changed. We propose that in S. platensis CO2 could act promoting degradation of pigments synthetised in excess in normal CO2 conditions, that are not necessary for light harvesting. Nitrogen assimilation was significantly not affected by CO2, and it is proposed that the inability to stimulate N assimilation by CO2 enrichment determined the lack of response in maximum growth rate.

Effect of zinc nutritional status on activities of superoxide radical and hydrogen peroxide scavenging enzymes in bean leaves

Abstract: The effect of varied zinc (Zn) supply on the activities of Superoxide dismutase (SOD), ascorbate (AsA) peroxidase, glutathione (GSSG) reductase, catalase and guaiacol peroxidase was studied in leaves of bean (Phaseolus vulgaris) plants grown for 15 days in nutrient solution. Zinc deficiency severely decreased plant growth and the leaf concentrations of soluble protein and chlorophyll. Resupply of Zn to deficient plants for up to 72h restored protein concentrations more rapidly than chlorophyll and plant growth. With the exception of guaiacol peroxidase, the activities of all enzymes were significantly decreased by Zn deficiency, in particular GSSG reductase and SOD. Within 72h of resupplying Zn to deficient plants, the enzyme activities reached the level of the Zn sufficient plants.The results indicate severe impairment in the ability of Zn-deficient leaves to enzymically scavenge O2 and H2O2. Consequences and reasons of this impairment are discussed in terms of photooxidation of chloroplast pigments and inhibition of the biosynthesis of the related scavenger enzyme proteins.

Is photosynthesis suppressed at higher elevations due to low CO2 pressure

Abstract: plant cell cultures Proceedings of the National Academy of Sciences (USA) 89:2389-2393 Haukioja, E, J Suomela, and S Neuvonen 1985 Longterm inducible resistance in birch foliage: triggering cues and efficacy on a defoliator Oecologia 65:363-369 Karban, R, and J Meyers 1989 Induced plant responses to herbivory Annual Review of Ecology and Systematics 20:331-348 Parsons, T, H Bradshaw, and M Gordon 1989 Systemic accumulation of specific mRNAs in response to wounding in poplar trees Proceedings of the National Academy of Sciences (USA) 86:7895-7899 Penia-Cortes, H, T Albrecht, S Prat, E Weiler, and L Willmitzer 1993 Aspirin prevents wound-induced gene-expression in tomato leaves by blocking jasmonic acid biosynthesis Planta 191:123-128 Rhoades, D 1983 Responses of alder and willow to attack by tent caterpillars and webworms: Evidence for pheromonal sensitivity of willows American Chemical Society Symposium Series 208:55-68 Schr6der, J, F Kreuzaler, E Schafer, and K Hahlbrock 1979 Concomitant induction of phenylalanine ammonialyase and flavanone synthase mRNAs in irradiated plant cells Journal of Biological Chemistry 254:57-65 Staswick, P 1992 Jasmonate, genes, and fragrant signals Plant Physiology 99:804-807 Zeringue, H 1987 Changes in cotton leaf chemistry induced by volatile elicitors Phytochemistry 26:1357-1360