Showing papers on "Plant physiology published in 2001"

Handbook of plant and crop physiology

Abstract: Plants, Crops, and Growth Environment: Nutrient Uptake by Plants Plant Water Relationships Current Perspectives in Water Loss from Plants and Stomatal Action Physiology of Plant/Crop Growth and Developmental Stages: Germination and Emergence Cell Cycle Control in Plants Vegetative and Elongation Growth Stages Ecophysiological Aspects of the Vegetative Propagation of Salt-bush (Atriplex spp) and Mulberry (Morus spp). Plant Growth Regulators - The Natural Hormones (Growth Promoters and Inhibitors) Physiological Responses of Plants and Crops Under Stressful (Salt, Drought, and Other Environmental Stress) Conditions: Physiological Adaptation of Plants to Environmental Stresses Adaptive Components of Salt Tolerance Photosynthesis In Plant/Crops Under Water and Salt Stress Physiological Mechanisms of Nitrogen Absorption and Assimilation in Plants Under Stressful Conditions. Physiology of Lower-Plant Genetics and Development: Developmental Genetics In Lower Plants. Physiology of Higher-Plant/Crop Genetics and Development: Transpiration Efficiency - Avenues for Genetic lmprovement, Physiological Mechanisms Relevant to Genetic Improvement of Salinity Tolerance in Crop Plants. Whole Plant vs Reductive Research on Physiological Genetics of Crop Physiology: Whole-System Research Complements Reductive Research, AMMI Statistical Model and Interaction Analysis, Photoperiod x Temperature Interaction Effects on the Days to Flowering of Bean (Phaseolus vulgaris L.) Genotype, Temperature and Genotype x Temperature Interaction Effects on Yield of Bean (Phaseolus vulgaris L) Control of Days to Flowering of Bean (Phaseolus vulgaris L) by Interaction of a Photoperiod Gene and a Non-photoperiod Gene. Physiological Aspects of Sustainable Plant/Crop Production: Sustainable Primary Production - Green Crop Fractionation: Effects of Species, Growth Conditions, and Physiological Development of Fractionation Products. (Part Contents).

Influence of Potassium Deficiency on Photosynthesis, Chlorophyll Content, and Chloroplast Ultrastructure of Cotton Plants

Abstract: In cotton (Gossypium hirsutum L) grown in controlled-environment growth chamber the effects of K deficiency during floral bud development on leaf photosynthesis, contents of chlorophyll (Chl) and nonstructural saccharides, leaf anatomy, chloroplast ultrastructure, and plant dry matter accumulation were studied After cotton plants received 35-d K-free nutrient solution at the early square stage, net photosynthetic rate (PN) of the uppermost fully expanded main-stem leaves was only 23 % of the control plants receiving a full K supply Decreased leaf PN of K-deficient cotton was mainly associated with dramatically low Chl content, poor chloroplast ultrastructure, and restricted saccharide translocation, rather than limited stomata conductance in K-deficient leaves Accumulation of sucrose in leaves of K-deficient plants might be associated with reduced entry of sucrose into the transport pool or decreased phloem loading K deficiency during squaring also dramatically reduced leaf area and dry matter accumulation, and affected assimilate partitioning among plant tissues

Gibberellins and Light-Stimulated Seed Germination.

Abstract: Bioactive gibberellins (GAs) promote seed germination in a number of plant species. In dicots, such as tomato and Arabidopsis, de novo GA biosynthesis after seed imbibition is essential for germination. Light is a crucial environmental cue determining seed germination in some species. The red (R) and far-red light photoreceptor phytochrome regulates GA biosynthesis in germinating lettuce and Arabidopsis seeds. This effect of light is, at least in part, targeted to mRNA abundance of GA 3-oxidase, which catalyzes the final biosynthetic step to produce bioactive GAs. The R-inducible GA 3-oxidase genes are predominantly expressed in the hypocotyl of Arabidopsis embryos. This predicted location of GA biosynthesis appears to correlate with the photosensitive site determined by using R micro-beam in lettuce seeds. The GA-deficient non-germinating mutants have been useful for studying how GA stimulates seed germination. In tomato, GA promotes the growth potential of the embryo and weakens the structures surrounding the embryo. Endo-b-mannanase, which is produced specifically in the micropylar endosperm in a GA-dependent manner, may be responsible for breaking down the endosperm cell walls to assist germination. Recently, a role for GA in overcoming the resistance imposed by the seed coat was also suggested in Arabidopsis from work with a range of seed coat mutants. Towards understanding the GA signaling pathway, GA response mutants have been isolated and characterized, some of which are affected in GA-stimulated seed germination.

Light Regulation of Gibberellin Biosynthesis and Mode of Action.

Abstract: Some phenotypic effects produced in plants by light are very similar to those induced by hormones. In this review, the light-gibberellin (GA) interaction in germination, de-etiolation, stem growth, and tuber formation (processes regulated by GAs) are discussed. Germination of lettuce and Arabidopsis seeds depends on red irradiation (R), which enhances the expression of GA 3-oxidase genes (GA3ox) and leads to an increase in active GA content. De-etiolation of pea seedling alters the expression of GA20ox and GA3ox genes and induces a rapid decrease of GA 1 content. Stem growth of green plants is also affected by diverse light irradiation characteristics. Low light intensity increases stem elongation and active GA content in pea and Brassica. Photoperiod controls active GA levels in long-day rosette (spinach and Silene) and in woody plants (Salix and hybrid aspen) by regulating different steps of GA biosynthesis, mainly through transcript levels of GA20ox and GA3ox genes. Light modulation of stem elongation in light-grown plants is controlled by phytochrome, which modifies GA biosynthesis and catabolism (tobacco, potato, cowpea, Arabidopsis) and GA-response (pea, cucumber, Arabidopsis). In Arabidopsis and tobacco, ATH1 (a gene encoding an homeotic transcription factor) is a positive mediator of a phyB-specific signal transduction cascade controlling GA levels by regulating the expression of GA20ox and GA3ox. Tuber formation in potato is controlled by photoperiod (through phyB) and GAs. Inductive short-day conditions alter the diurnal rhythm of GA20ox transcript abundance, and increases the expression of a new protein (PHOR1) that plays a role in the photoperiod-GA interaction.

Aluminum resistance in two cultivars of Zea mays L.: Root exudation of organic acids and influence of phosphorus nutrition

Abstract: Root exudation of organic acids as Al-chelating compounds and P nutrition have been suggested to play a major role in Al-resistance in higher plants Effects of Al exposure on maize plant growth, and organic acid root content and root exudation under various levels of P nutrition were examined Sikuani, a Colombian maize cultivar tolerant to acid soils with high Al saturation, and Corso, a Swiss cultivar, were grown in sterile hydroponic conditions for 21 days Al-caused inhibition of root growth was lower in Sikuani than in Corso Al effect on plant growth was decreased with increasing P content in roots Al content in roots increased with increasing P content and was higher in Sikuani than in Corso When exposed to Al, the contents in root apices as well as the root exudation of citric and malic acids in Corso and citric, malic and succinic acids in Sikuani increased, and were higher in Sikuani than in Corso Increased PEP carboxylase (PEPC) activity in root apices after Al exposure partially explained the variations of organic acid content in the roots These Al-induced changes in PEPC activity, organic acid content and exudation were reduced in plants supplied with higher P concentrations during the 21 days prior to treatment Increased secretion of organic acids after exposure to Al appeared to be specific to Al and was not totally explained by increased root content in organic acids

Increased heat sensitivity of photosynthesis in tobacco plants with reduced Rubisco activase.

Abstract: High temperature inhibits photosynthesis by several mechanisms including deactivation of Rubisco. The inhibition of photosynthesis by high temperature and its relationship to Rubisco deactivation was studied using tobacco (Nicotiana tabaccum L. cv W38) transformed with a Rubisco activase gene inserted in the antisense orientation and untransformed controls. High temperature (42 degrees C) reduced photosynthesis in both lines of plants. However, photosynthesis recovered nearly completely in wild-type plants and very little in plants lacking Rubisco activase. The F(0)' level of chlorophyll fluorescence decreased and q(N) increased in the control plants during heating. In the antisense plants, q(N) was always high and F(0)' increased slightly during heat stress. NADP-malate dehydrogenase activation was unaffected by heat stress in control plants but was increased in the transgenic plants, consistent with a high redox status in the chloroplast. In wild-type plants, the inhibition of photosynthesis could be explained by a reversible decarbamylation of Rubisco and an acceptor-side limitation imposed on photosynthetic electron transport. However, in the anti-activase plants, carbamylation was low and constant and could not explain how photosynthesis was reduced at high temperature. Because ribulose bisphosphate was saturating at high temperature, the reduction in photosynthesis must have been caused by some impairment of Rubisco function not reflected in measurements of activation state or carbamylation status. This in vivo Rubisco impairment was not relieved upon return to lower temperature. We speculate that the reversible decarbamylation of Rubisco at moderately high temperature may be a protective mechanism by which the plant avoids more serious effects on Rubisco and the rest of the photosynthetic apparatus.

Plant Water Relationships

Abstract: Life is intimately associated with water, and particularly with water in its liquid phase. Water is the form in which the H atom, an essential element of all organic molecules, is absorbed and then assimilated in the course of photosynthesis (page 147). About 500 g of water is absorbed by roots to produce 1g organic material and thus may be considered as a plant nutrient, in the same way as CO2 or NO 3 − are also plant nutrients. The quantity of water required for the photosynthetic process, however, is small and amounts to only about 0.01% of the total quantity of water used by the plant. Most functions in which plant water is involved, are of a physical nature. Water is a solvent for many substances such as inorganic salts, sugars and organic anions. It is also the medium in which all biochemical reactions take place. Water molecules are adsorbed at the surfaces of particles forming hydration shells, which influence physical and chemical reactions. Water in liquid form allows the diffusion and mass flow of solutes, and for this reason is essential for the translocation and distribution of nutrients and metabolites throughout the entire plant. Water is also important in the vacuoles of plant cells as it generally exerts an intracellular pressure on the protoplasm and cell wall (so called turgor pressure) thus maintaining the rigidity of leaves, roots and other plant organs. These few examples indicate the overall importance of water in plant physiology.

Genetic dissection of blue-light sensing in tomato using mutants deficient in cryptochrome 1 and phytochromes A, B1 and B2

Abstract: Several novel allelic groups of tomato (Solanum lycopersicum L.) mutants with impaired photomorphogenesis have been identified after gamma-ray mutagenesis of phyA phyB1 double-mutant seed. Recessive mutants in one allelic group are characterized by retarded hook opening, increased hypocotyl elongation and reduced hypocotyl chlorophyll content under white light (WL). These mutants showed a specific impairment in response to blue light (BL) resulting from lesions in the gene encoding the BL receptor cryptochrome 1 (cry1). Phytochrome A and cry1 are identified as the major photoreceptors mediating BL-induced de-etiolation in tomato, and act under low and high irradiances, respectively. Phytochromes B1 and B2 also contribute to BL sensing, and the relative contribution of each of these four photoreceptors differs according to the light conditions and the specific process examined. Development of the phyA phyB1 phyB2 cry1 quadruple mutant under WL is severely impaired, and seedlings die before flowering. The quadruple mutant is essentially blind to BL, but experiments employing simultaneous irradiation with BL and red light suggest that an additional non-phytochrome photoreceptor may be active under short daily BL exposures. In addition to effects on de-etiolation, cry1 is active in older, WL-grown plants, and influences stem elongation, apical dominance, and the chlorophyll content of leaves and fruit. These results provide the first mutant-based characterization of cry1 in a plant species other than Arabidopsis.

Bioenergetic and metabolic processes for the survival of sulfur-deprived Dunaliella salina (Chlorophyta)

Abstract: The work addressed bioenergetic, metabolic and physiological responses ofthe green alga Dunaliella salina to sulfur (S)-deprivation. Photo-autotrophically grown cells were suspended in a medium in which thesulfates were replaced by chloride salts. Growth characteristics, pigmentcontent, rates of photosynthesis and respiration, as well as endogenoussubstrate (starch and protein) accumulation were monitored as a functionof time under S-deprivation. Lack of S from the growth medium had adifferential effect on photosynthesis and respiration. The rate oflight-saturated photosynthesis declined semi-exponentially with time,whereas the activity of respiration remained fairly constant over a periodof up to 100 h in S-deprived medium. Cell division and `packed cell volumeincrease' declined in tandem with the decline in the rate of photosynthesis. There was gradual loss of chlorophyll from the cells and a concomitant lossof photochemically competent system-II reaction centers, whereas theconcentration of system-I remained largely unaffected under S-deprivation. Cells altered the partition of photosynthate between starch and protein sothat control steady-state starch/protein ratios in the light (0.1: 1, w: w)gradually increased up to about 1: 1 as a function of S-deprivation. SealedDunaliella salina cultures, in which the capacity of photosynthesisdeclined to levels lower than that of respiration, consumed dissolvedoxygen and became anaerobic in the light. These cultures, however, did notactivate the reversible `hydrogenase pathway' and did not produceH2 gas. Instead, under extended S-deprivation, cells maintained alow-level cycling of O2 and CO2 between photosynthesis andrespiration that resulted in no net exchange of gases. Such low-level cyclingof photosynthesis and respiration was sufficient to ensure the generation ofATP needed for survival of the organism under protracted S-deprivationconditions.

Changes in the Levels of γ-Aminobutyric Acid and Glutamate Decarboxylase in Developing Soybean Seedlings

Abstract: The changes in the levels of 7-aminobutyric acid (GABA), glutamic acid (Glu), calcium ions, and calmodulin as well as glutamate decarboxylase (GAD) activities were investigated in developing soybean seedlings. The GABA level determined was 12.3% of total free amino acids in the apical regions of roots, whereas it was only 4.2% of total free amino acid in cotyledons. The apical regions of roots also contained significantly higher levels of GAD, compared with cotyledons and mature base tissues. The Glu level was 13% of total free amino acids in the cotyledons, whereas it was only about 0.2% of total free amino acids in the apical regions. Calcium and calmodulin were found higher in cotyledons and the apical regions, compared with other parts of the seedlings. These data indicate that in develop ing soybean seedlings the levels of GABA and GABA synthesis activity are highest in the youngest tissues.

Alteration in growth and some relevant metabolic processes of broad bean plants during extreme temperatures exposure

Abstract: The effect of heat-shock (42 °C) or chilling-shock (5 °C) on growth and some relevant metabolic changes of broad bean (Vicia faba L.) were studied. Both heat and chilling-stress induced a reduction in growth rate, membrane stability and content of photosynthetic pigments (chlorophyll a, b and carotenoids). K+ efflux and UV absorbance increased at increasing or decreasing temperature. Considerable variations in the content of cell-wall components (pectin, cellulose, hemicellulose and lignin), cell-wall associated proteins, soluble sugars, starch, total lipids, glycolipids, phospholipids and sterols were induced by extreme temperure.

Altered development of Arabidopsis thaliana carrying the Agrobacterium tumefaciens ipt gene is partially due to ethylene effects

Abstract: Transgenic Arabidopsis thaliana plants containingthe Agrobacterium tumefaciens cytokinin-biosynthesis geneipt were produced to study the effect of increasedcytokinin (CK) levels on the development of this rosette plant species. Inthreeindependently transformed lines (ipt-156, 158 and 161),Arabidopsis plants had smaller leaves, an underdevelopedroot system and decreased apical dominance in inflorescence stems. The smallertransgenic leaves were highly serrated along the margins, pale green and hadpointed leaf tips. In cross section, transgenic leaves had smaller cells andirregularly shaped epidermal cells. In the ipt-161 line,leaves and hypocotyls frequently exhibited purple color due to anthocyaninproduction. The most severe phenotype was observed in tissue cultureconditions,while growth in soil reduced or eliminated some phenotypic effects. Compared toC24 wild type plants, ipt-161 plants accumulated zeatinandzeatin riboside with an approximate 10-fold increase in the total pool of CKs.Astudy of the progeny resulting from crosses between theipt-161 transgenic line and the ethylene insensitivemutants ein1, ein2 andeti5 suggested that part of the altered developmentexhibited by the ipt transgenic plants was caused byincreased ethylene levels.

Effects of Light Spectral Quality on Morphogenesis and Source–Sink Relations in Radish Plants

Abstract: The accumulation of dry matter and the content of major phytohormones in the aboveground and underground plant parts, as well as light curves and the diurnal course of photosynthesis in the leaves were studied in radish (Raphanus sativusL.) plants of different ages that were grown under red (RL) or blue (BL) light. As seen from the rapid increase in plant biomass, the development of storage organs (hypocotyl or tap root) started on the 14th day after the emergence of seedling of the BL plants and on the 21st day for the RL plants. Conversely, RL stimulated biomass accumulation in the aboveground parts (petioles and stems) already in the early stages of plant development. Light spectral quality only slightly affected the activity and the diurnal course of photosynthesis. The GA content was ten times higher in the aboveground parts of the RL plants than those of the BL plants. The hypocotyl of the BL plants contained much higher amounts of cytokinins and IAA than that of the RL plants. The specific responses of the source–sink relations to the light quality were related to the distribution of various phytohormones between the aboveground and underground parts of the plants: RL increased the content of gibberellins (GA) in the aboveground parts of plants, thus increasing their sink activity, whereas BL stimulated the synthesis of cytokinins and IAA in the hypocotyl and enhanced its development. Light quality-specific morphogenetic responses were reversed when plants were treated with exogenous GA or paclobutrazol, an inhibitor of GA synthesis. The treatment of the BL plants with exogenous GA stimulated petiole and hypocotyl elongation and induced stem formation. The treatment of the BL plants with paclobutrazol led to shortened petioles, the flattening of the storage organ, and the disappearance of the stem.

Selective plant growth suppression by shoot application of soil bacteria

Abstract: Selected rhizosphere bacterial isolates, previously determined as plant growth deleterious, were tested for their ability to suppress plant growth after foliar spray applications, for selectivity with regard to plant species, and in pilot field experiments for their potential as weed biocontrol agents. Inundative foliar applications of aqueous bacterial suspension were performed on a range of weed and crop species. Plant symptoms after spraying ranged from rapid necrosis and wilting to an overall growth suppression or stunting. Significant and selective reductions in biomass of up to 90% fresh weight, as well as large reductions in plant survival and plant height were recorded in greenhouse pot experiments. However, monocotyledonous plants were affected weakly or not at all by two isolates extensively tested. Effects of these were dose- and plant age-dependent, and were for some plants enhanced by high relative humidity. For one isolate, A153, effects were also expressed in cell-free culture filtrates pointing to involvement of specific metabolites. In pilot field experiments, strong growth suppression was observed on broad-leaved plants, while barley crop plants were unaffected.

Ethylene and Cytokinin in the Control of Senescence in Detached Leaves of Arabidopsis thaliana eti-5Mutant and Wild-Type Plants

Abstract: We studied the effects of cytokinin benzyladenine (BA) and ethylene on the senescence in the dark of detached leaves of Arabidopsis thaliana(L.) Heynh wild-type plants and theeti-5mutant, which was described in the literature as the ethylene-insensitive one. Leaf senescence was assessed from a decrease in the chlorophyll content. The content of endogenous cytokinins (zeatin and zeatin riboside) was estimated by the ELISA technique. We demonstrated that the content of endogenous cytokinins in the leaves of the three-week-old eti-5mutants exceeded that of the wild-type leaves by an order of magnitude; in the five-week-old mutants, by several times; and in the seven-week-old plants, the difference became insignificant. Due to the excess of endogenous cytokinins in the three–five-week-old mutant leaves, their senescence in the dark was retarded and exogenous cytokinin affected these leaves to a lesser extent. The seven-week-old mutant and the wild-type leaves, which contained practically similar amounts of endogenous cytokinins, did not differ in these indices. Thus, the level of endogenous cytokinins determined the rate of senescence and the leaf response to cytokinin treatment. Ethylene accelerated the senescence of detached wild-type leaves. Ethylene action increased with increasing its concentration from 0.1 to 100 μl/l. BA (10–6M) suppressed ethylene action. Similar data were obtained for the eti-5mutant leaves. We therefore suggest that the mutant leaves comprised the pathways of the ethylene signal reception and transduction, which provided for the acceleration of their senescence.

Pre-Treatment of Bean Seedlings with Choline Compounds Increases the Resistance of Photosynthetic Apparatus to UV-B Radiation and Elevated Temperatures

Abstract: Bean (Phaseolus vulgaris L. cv. Berbukskaya) seedlings were pre-treated with choline compounds, 19 mM 2-ethyltrimethylammonium chloride (Ch) or 1.6 mM 2-chloroethyltrimethylammonium chloride (CCh), during 24 h, then after 6 d the excised primary leaves were exposed to UV-B and high temperature stress. Chlorophyll (Chl) fluorescence, delayed light emission, accumulation of photosynthetic pigments, contents of thiobarbituric acid reactive substances, and activities of the active oxygen detoxifying enzymes (superoxide dismutase, ascorbate peroxidase, and glutathione reductase) were examined. Pre-treatment of plants with Ch or CCh enhanced the resistance of photosystem 2 (PS2) photochemistry to UV-B and heat injuries. The higher stress resistance can be explained by the increased activity of the detoxifying enzymes. The increased content of UV-B-absorbing pigments may also contribute to the enhanced resistance of choline-treated plants to UV-B radiation.

Effects of Irradiance-Sulphur Interactions on Enzymes of Carbon, Nitrogen, and Sulphur Metabolism in Maize Plants

Abstract: The effect of sulphur deprivation and irradiance (180 and 750 µmol m−2 s−1) on plant growth and enzyme activities of carbon, nitrogen, and sulphur metabolism were studied in maize (Zea mays L. Pioneer cv. Latina) plants over a 15-d-period of growth. Increase in irradiance resulted in an enhancement of several enzyme activities and generally accelerated the development of S deficiency. ATP sulphurylase (ATPs; EC 2.7.7.4) and o-acetylserine sulphydrylase (OASs; EC 4.2.99.8) showed a particular and different pattern as both enzymes exhibited maximum activity after 10 d from the beginning of deprivation period. Hence in maize leaves the enzymes of C, N, and S metabolism were differently regulated during the leaf development by irradiance and sulphur starvation.

Hydrogen peroxide contents and activities of antioxidative enzymes among C3, C4 and CAM plants

Abstract: Leaves of nine, seven and nine species, respectively, of C3, C4 and CAM plants, under usual growing conditions, were collected to determine H2O2 content and the activities of oxygen-scavenging enzymes. H2O2 content in leaves of C4 plants was similar to that of C3 plants, whereas that of CAM plants was higher. The superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) activities were higher in C3 plants compared to those of CAM plants. C4 plants exhibited higher APX but lower CAT activities than C3 plants ; however, both activities were higher than those of CAM plants. Our findings indicate that oxygen-scavenging systems in plants, such as those involving H2O2, differ from their photosynthetic capacities.

Morphophysiological Indices of the Source Leaf in Wheat Plants Acclimated to Conditions of Nitrogen Nutrition

Abstract: Growth, leaf and cell morphology, and the chemical composition of the second leaf were studied in wheat (Triticum aestivumL., cv. Inna) plants grown on the medium containing nitrate, ammonium, or no nitrogen at all. Independent of the nitrogen nutrition, the second leaf of the 21-day-old plants matures and functions as a source of assimilates. Both ammonium nutrition and nitrogen deficiency decreased the fresh weight, area, and cell size in the leaf; however, the conditions of nitrogen nutrition did not affect the dry weight of the leaf. Nitrogen starvation increased and ammonium nutrition decreased the relative content of the cell walls in the dry weight. In the nitrate-fed plants, the leaf content of sucrose increased, and the contents of reduced nitrogen (Nred) and protein were lower than in the ammonium treatment. Reciprocally, the contents of reduced nitrogen and protein were highest in the ammonium treatment, the content of sucrose was lowest, with starch practically absent from the leaf. The nitrogen-starved leaf accumulated a large amount of starch, the Nredcontent was two times lower than in the ammonium-fed plants, and the protein content was similar to that in the nitrate-fed plants. Thus, leaf and cell morphology and the content of Nred, protein, and carbohydrate changes in different ways during wheat acclimation to the condition of nitrogen nutrition. By assessing the cell wall weight, the authors established that, depending on nitrogen nutrition, this cell compartment accepts a variable flow of carbon.

Instant notes plant biology

Abstract: Section A - INTRODUCTION. Section B - STRUCTURE. The plant cell. The cell wall. Plastids and mitochondria. Membranes. Nucleus and genome. Cell Division. Section C - VEGETATIVE ANATOMY. Meristems and primary tissues. Roots. Herbaceous stems and primary growth. Woody stems and secondary growth. Leaves. Section D - REPRODUCTIVE ANATOMY. The flower. Pollen and ovlules. The seed. Fruits. Section E - PHYSIOLOGY AND REGULATION. Arabidopsis and other model plants. Methods in experimental plant science. Section F - GROWTH AND DEVELOPMENT. Features of growth and development. Biochemistry of growth regulation. Molecular action of hormones and intracellular messengers. Section G - SENSING AND RESPONDING TO THE ENVIRONMENT. Phytochrome, photoperiodism and photomorphogenesis. Tropisms. Nastic responses. Abscission. Stress avoidance and adaptation. Section H - FLORAL DEVELOPMENT AND REPRODUCTIVE PHYSIOLOGY. Physiology of floral initiation and development. Breeding systems. Self incompatibility. Seed development, dormancy and germination. Section I - PLANTS, WATER AND MINERAL NUTRITION. Plants and water. Water retention and stomata. Movement of nutrient ions across membranes. Uptake of mineral nutrients in the plant. Functions of mineral nutrients. Section J - METABOLISM. Photosynthetic pigments and the nature of light. Major reactions of photosynthesis. C3 and C4 plants and CAM. Respiration and carbohydrate metabolism. Amino acid, lipid, polysaccharide and secondary product metabolism. Section K - PLANT COMMUNITIES AND POPULATIONS. Physical factors and plant distribution. Plant communities. Ecology of different growth forms. Populations. Contributions to carbon balance and atmosphere. Section L - REPRODUCTIVE ECOLOGY. Ecology of flowering and pollination. Seed ecology. Regeneration and establishment. Polymorphisms and population genetics. Section M - INTERACTIONS BETWEEN PLANTS AND OTHER ORGANISMS. Mycorrhiza. Nitrogen fixation. Interactions between plants and animals. Fungal pathogens and endophytes. Bacteria, mycoplasma, viruses and heterokonts. Parasites and saprophytes. Carnivorous plants. Section N - HUMAN USES OF PLANTS. Plants as food. Plants for construction. Plants in medicine. Plants for other uses. Bioremediation. Section O - PLANT GENETIC ENGINEERING AND BIOTECHNOLOGY. Plant breeding. Plant cell and tissue culture. Plant genetic engineering. Section P - PLANT DIVERSITY. Diversity and life cycles. The algae. The bryophytes. Reproduction in bryophytes. Section Q - SPORE-BEARING VASCULAR PLANTS. Early evolution of vascular plants. Clubmosses and horsetails. The ferns. Evolution of the seed. Section R - SEED PLANTS. Early seed plants. Conifers. Cycads, Gingko and Gnetales. Evolution of flowering plants. Mechanisms of evolution. Further reading. Index

Structural and Functional Characteristics of Ajuga reptansPhotosynthesis under Cold Climate Conditions

Abstract: Structural, functional, and biochemical characteristics of the photosynthetic apparatus of a nemoral herbaceous perennial plant Ajuga reptansL. inhabiting the middle taiga subzone were investigated. Plant leaves were characterized by a high content of green (3.1 mg/dm2) and yellow (0.64 mg/dm2) pigments and contained moderate-sized chloroplasts with grana consisting of ten thylakoids or more. The maximum rate of photosynthesis in summergreen leaves (5–8 mg CO2/(dm2h)) was observed at 14–16°C under a saturating photosynthetically active radiation of 50 W/m2. At 6–7°C, the rate of CO2assimilation was reduced to 60–80% of the maximum one. The temperature optimum of photosynthesis was not constant and shifted by 2–6°C depending on the changes in the ambient temperature. Wintergreen leaves were capable of photosynthesis in late autumn after heavy freezes and in early spring after a long winter. The accumulation of soluble carbohydrates and free amino acids in leaves helps to maintain the functional activity of the photosynthetic apparatus.

The Biogenesis of the Photosynthetic Apparatus and the Activity of Chlorophyll Biosynthesis in a Plastome Mutant of Sunflower

Abstract: It was demonstrated that, in the phenotypically colorless leaves of a sunflower (Helianthus annuusL) plastome mutant with a heavily reduced level of chlorophyll, all pigment–protein complexes of the photosynthetic apparatus typical for the wild type were present However, the ratio between them was changed During aging of the mutant leaves, pigment–protein complexes of photosystem I were destroyed first followed by those of photosystem II Chlorophyll a/b-containing light-harvesting complex II turned out to be the most stable This conforms to an increased content of lutein and violaxanthin in mutant leaves A synchrony of the decreases in the chlorophyll and 5-aminolevulinic acid (ALA) contents throughout all ontogenetic stages of the colorless mutant leaves made it possible to suggest that a decrease in the synthesis and resynthesis of chlorophyll during the formation and development of such leaves is caused by the inhibition of an initial stage of this process, namely, the biosynthesis of ALA molecules The activity of the enzymes converting ALA into protochlorophyllide did not limit chlorophyll biosynthesis Possible mechanisms controlling the synthesis of ALA destined for chlorophyll formation are discussed

Activity of the Fe-Branch of Tetrapyrrole Biosynthesis in the Chlorophyll-Deficient Plastome Mutant of Sunflower

Abstract: The biosynthesis of heme, a plant tetrapyrrole, was studied in the leaves of a chlorophyll-deficient plastome mutant of the sunflower (Helianthus annuus L, line 2-24, albina form). In the light, the content of 5-aminolevulinic acid (ALA) in white mutant leaves was, on the average, ten times less than in that of the wild-type form (line 3629). Chlorophyll content in mutant leaves comprised only 0.3% of that of control plants. The activities of Fe-chelatase and ALA dehydratase in the heme synthesis were either comparable to or even higher than those in the wild-type leaves. A normal respiration rate in white mutant leaves, the equal content of phytochrome apoproteins in plants of both types, and the lack of noticeable morphogenetic differences realized through the phytochrome system can indicate that mutant and wild-type leaves are similar in their levels of phytochrome and the cytochromes of mitochondrial respiration. Nevertheless, in the mutant, the content of heme noncovalently bound by apoproteins amounted to only one third of its content in the wild-type plants. It seems that a dramatic decrease in the capability of white leaves for chlorophyll biosynthesis and for the formation of the photosynthetic apparatus is responsible for a low demand for chloroplast cytochromes, which is the major cause of a reduced heme content in the mutant.

The Response of Plastidome and Chondriome in Leaf Chlorenchyma to Prolonged Atmospheric Pollution

Abstract: The quantitative changes in the major organelles, chloroplasts and mitochondria, were followed in order to evaluate plant cell responses to prolonged atmospheric pollution. Chlorenchyma cells were compared in needle and leaves of evergreen (Pinus sylvestris, Arctostaphylos uva-ursi, and Vaccinium vitis-idaea), deciduous (Betula pubescens, V. myrtillus, and V. uliginosum), and herbaceous (Cornus suecica, Potentilla erecta, and Solidago lapponica) plants growing at distances of 65 to 70 km (an undisturbed habitat) and 8 to 10 km (a heavily damaged habitat) from the “Severonikel” industrial complex in the town of Monchegorsk on the Kola peninsula. Chlorenchyma cells with the structure undamaged by atmospheric pollination were used for comparison. In undamaged (depressed) chlorenchyma cells of needles and leaves affected by heavy pollination, the morphometric analysis showed that the chloroplast density did not change, while the mitochondrial density increased in most species under study. The considerable increase in the number of mitochondria in the depressed chlorenchyma cells of needles and leaves in evergreen plant species seems to constitute the mechanism for plant compensation under prolonged stress conditions.