Showing papers on "Shoot published in 2002"

[Responses of agricultural crops of free-air CO2 enrichment].

Abstract: Over the past decade, free-air CO2 enrichment (FACE) experiments have been conducted on several agricultural crops: wheat(Triticum aestivum L.), perennial ryegrass (Lolium perenne), and rice(Oryza sativa L.) which are C3 grasses; sorghum (Sorghum bicolor (L.) Moench), a C4 grass; white clover (Trifolium repens), a C3 legume; potato (Solanum tuberosum L.), a C3 forb with tuber storage; and cotton (Gossypium hirsutum L.) and grape (Vitis vinifera L.) which are C3 woody perennials. Using reports from these experiments, the relative responses of these crops was discussed with regard to photosynthesis, stomatal conductance, canopy temperature, water use, water potential, leaf area index, shoot and root biomass accumulation, agricultural yield, radiation use efficiency, specific leaf area, tissue nitrogen concentration, nitrogen yield, carbohydrate concentration, phenology, soil microbiology, soil respiration, trace gas emissions, and soil carbon sequestration. Generally, the magnitude of these responses varied with the functional type of plant and with the soil nitrogen and water status. As expected, the elevated CO2 increased photosynthesis and biomass production and yield substantially in C3 species, but little in C4, and it decreased stomatal conductance and transpiration in both C3 and C4 species and greatly improved water-use efficiency in all the crops. Growth stimulations were as large or larger under water-stress compared to well-watered conditions. Growth stimulations of non-legumes were reduced at low soil nitrogen, whereas elevated CO2 strongly stimulated the growth of the clover legume both at ample and under low N conditions. Roots were generally stimulated more than shoots. Woody perennials had larger growth responses to elevated CO2, while at the same time, their reductions in stomatal conductance were smaller. Tissue nitrogen concentrations went down while carbohydrate and some other carbon-based compounds went up due to elevated CO2, with leaves and foliage affected more than other organs. Phenology was accelerated slightly in most but not all species. Elevated CO2 affected some soil microbes greatly but not others, yet overall activity appears to be stimulated. Detection of statistically significant changes in soil organic carbon in any one study was impossible, yet combining results from several sites and years, it appears that elevated CO2 did increase sequestration of soil carbon. Whenever possible, comparisons were made between the FACE results and those from prior chamber-based experiments reviewed in the literature. Over all the data and parameters considered in this review, there are only two parameters for which the FACE- and chamber-based data appear to be inconsistent. One is that elevated CO2 from FACE appears to reduce stomatal conductance about one and a half times more than observed in prior chamber experiments. Similarly, elevated CO2 appears to have stimulated root growth relatively more than shoot growth under FACE conditions compared to chamber conditions. Nevertheless, for the most part, the FACE- and chamber-based results have been consistent, which gives confidence that conclusions drawn from both types of data are accurate. However, the more realistic FACE environment and the larger plot size have enabled more extensive robust multidisciplinary data sets to be obtained under conditions representative of open fields in the future high-CO2 world.

MAX1 and MAX2 control shoot lateral branching in Arabidopsis

Abstract: Plant shoots elaborate their adult form by selective control over the growth of both their primary shoot apical meristem and their axillary shoot meristems. We describe recessive mutations at two loci in Arabidopsis, MAX1 and MAX2, that affect the selective repression of axillary shoots. All the first order (but not higher order) axillary shoots initiated by mutant plants remain active, resulting in bushier shoots than those of wild type. In vegetative plants where axillary shoots develop in a basal to apical sequence, the mutations do not clearly alter node distance, from the shoot apex, at which axillary shoot meristems initiate but shorten the distance at which the first axillary leaf primordium is produced by the axillary shoot meristem. A small number of mutant axillary shoot meristems is enlarged and, later in development, a low proportion of mutant lateral shoots is fasciated. Together, this suggests that MAX1 and MAX2 do not control the timing of axillary meristem initiation but repress primordia formation by the axillary meristem. In addition to shoot branching, mutations at both loci affect leaf shape. The mutations at MAX2 cause increased hypocotyl and petiole elongation in light-grown seedlings. Positional cloning identifies MAX2 as a member of the F-box leucine-rich repeat family of proteins. MAX2 is identical to ORE9, a proposed regulator of leaf senescence (Woo, H. R., Chung, K. M., Park, J.-H., Oh, S. A., Ahn, T., Hong, S. H., Jang, S. K. and Nam, H. G. (2001) Plant Cell 13, 1779-1790). Our results suggest that selective repression of axillary shoots involves ubiquitinmediated degradation of as yet unidentified proteins that activate axillary growth.

A meta-analysis of elevated [CO2] effects on soybean (Glycine max) physiology, growth and yield

Abstract: The effects of elevated [CO2] on 25 variables describing soyabean physiology, growth and yield are reviewed using meta-analytical techniques. This is the first meta-analysis to our knowledge performed on a single crop species and summarizes the effects of 111 studies. These primary studies include numerous soyabean growth forms, various stress and experimental treatments, and a range of elevated [CO2] levels (from 450 to 1250 ppm), with a mean of 689 ppm across all studies. Stimulation of soyabean leaf a CO2 assimilation rate with growth at elevated [CO2] was 39%, despite a 40% decrease in stomatal conductance and a 11% decrease in Rubisco [ribulose-bisphosphate carboxylase] activity. Increased leaf CO2 uptake combined with an 18% stimulation in leaf area to provide a 59% increase in canopy photosynthetic rate. The increase in total dry weight was lower at 37%, and seed yield still lower at 24%. This shows that even in an agronomic species selected for maximum investment in seed, several plant level feedbacks prevent additional investment in reproduction, such that yield fails to reflect fully the increase in whole plant carbon uptake. Large soil containers (>9 litres) have been considered adequate for assessing plant responses to elevated [CO2]. However, in open-top chamber experiments, soyabeans grown in large pots showed a significant threefold smaller stimulation in yield than soyabeans grown in the ground. This suggests that conclusions about plant yield based on pot studies, even when using very large containers, are a poor reflection of performance in the absence of any physical restriction on root growth. This review supports a number of current paradigms of plant responses to elevated [CO2]. Namely, stimulation of photosynthesis is greater in plants that fix N and have additional carbohydrate sinks in nodules. This supports the notion that photosynthetic capacity decreases when plants are N-limited, but not when plants have adequate N and sink strength. The root:shoot ratio did not change with growth at elevated [CO2], sustaining the charge that biomass allocation is unaffected by growth at elevated [CO2] when plant size and ontogeny are considered.

ABA, ethylene and the control of shoot and root growth under water stress

Abstract: The question of whether abscisic acid (ABA) acts as an inhibitor or promoter of shoot growth in plants growing in drying soil is examined, drawing on current understanding of the role of ABA in root growth maintenance. Particular consideration is given to studies of endogenous ABA deficiency, which have shown that an important role of ABA is to limit ethylene production, and that this interaction is involved in the effects of ABA status on shoot and root growth.

Improved tolerance of maize plants to salt stress by arbuscular mycorrhiza is related to higher accumulation of soluble sugars in roots.

Abstract: The effect of colonization with the arbuscular mycorrhizal (AM) fungus Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe on the growth and physiology of NaCl-stressed maize plants (Zea mays L. cv. Yedan 13) was examined in the greenhouse. Maize plants were grown in sand with 0 or 100 mM NaCl and at two phosphorus (P) (0.05 and 0.1 mM) levels for 34 days, following 34 days of non-saline pre-treatment. Mycorrhizal plants maintained higher root and shoot dry weights. Concentrations of chlorophyll, P and soluble sugars were higher than in non-mycorrhizal plants under given NaCl and P levels. Sodium concentration in roots or shoots was similar in mycorrhizal and non-mycorrhizal plants. Mycorrhizal plants had higher electrolyte concentrations in roots and lower electrolyte leakage from roots than non-mycorrhizal plants under given NaCl and P levels. Although plants in the low P plus AM fungus treatment and those with high P minus AM fungus had similar P concentrations, the mycorrhizal plants still had higher dry weights, soluble sugars and electrolyte concentrations in roots. Similar relationships were observed regardless of the presence or absence of salt stress. Higher soluble sugars and electrolyte concentrations in mycorrhizal plants suggested a higher osmoregulating capacity of these plants. Alleviation of salt stress of a host plant by AM colonization appears not to be a specific effect. Furthermore, higher requirement for carbohydrates by AM fungi induces higher soluble sugar accumulation in host root tissues, which is independent of improvement in plant P status and enhances resistance to salt-induced osmotic stress in the mycorrhizal plant.

Micrografting techniques for testing long-distance signalling in Arabidopsis

Abstract: Grafting in species other than Arabidopsis has generated persuasive evidence for long-distance signals involved in many plant processes, including regulation of flowering time and shoot branching. Hitherto, such approaches in Arabidopsis have been hampered by the lack of suitable grafting techniques. Here, a range of micrografting methods for young Arabidopsis seedlings are described. The simplest configuration was a single-hypocotyl graft, constructed with or without a supporting collar, allowing tests of root-shoot communication. More complex two-shoot grafts were also constructed, enabling tests of shoot-shoot communication. Integrity of grafts and absence of adventitious roots on scions were assessed using plants constitutively expressing a GUS gene as one graft partner. Using the max1 (more axillary growth) and max3 increased branching mutants, it was shown that a wild-type (WT) rootstock was able to inhibit rosette branching of mutant shoots. In two-shoot grafts with max1 and WT shoots on a max1 rootstock, the mutant shoot branched profusely, but the WT one did not. In two-shoot grafts with max1 and WT shoots on a WT rootstock, neither shoot exhibited increased branching. The results mirror those previously demonstrated in equivalent grafting experiments with the ramosus mutants in pea, and are consistent with the concept that a branching signal is capable of moving from root to shoot, but not from shoot to shoot. These grafting procedures will be valuable for revealing genes associated with many other long-distance signalling pathways, including flowering, systemic resistance and abiotic stress responses.

Effect of Salinity Stress on Growth and Nutrient Composition of Three Soybean (Glycine max L. Merrill) Cultivars

Abstract: Soil salinity is a major limitation to legume production in many areas of the world. The salinity sensitivity of soybean was studied to determine the effect of salinity on seed germination, shoot and root dry weights, and leaf mineral contents. Three soybean cultivars, Lee, Coquitt, and Clark 63, were planted in soils of different salinity levels. The electrical conductivity (EC) of the soils used in this experiment was 0.5 dS m−1. The soil salinity treatments were 0.5, 2.5 4.5, 6.5 and 8.5 dS m−1. Saline drainage water from a drainage canal with an EC of 15 dS m−1 was used to treat the soil samples in order to obtain the desired salinity levels. Germination percentages were recorded 10 days after planting. Shoot and root dry weights of 45-day-old plants were measured. Nutrient concentrations for Na+, K+, Ca2+, Mg2+ and Cl− were determined. Germination percentages were significantly reduced with increasing salinity levels. The cultivar Lee was less affected by salinity stress than Coquitt and Clark 63. At 8.5 dS m−1 a significant reduction in plant height was found in all three cultivars. However, Lee plants were taller than plants of the other two cultivars. Salinity stress induced a significant increase in leaf sodium (Na+) and chloride (Cl−) in all cultivars. However, the cultivar Lee maintained lower Na+ and Cl+ concentrations, a higher potassium (K+) concentration and a higher K+/Na+ ratio at higher salinity levels than Coquitt and Clark 63. Saline stress reduced the accumulation of K+, calcium (Ca2+) and magnesium (Mg2+) in the leaves of the cultivars studied. This study suggests that Lee is the most tolerant cultivar, and that there is a relationship between the salt tolerance of the cultivar and macronutrient accumulation in the leaves.

Seasonal changes in birch leaf chemistry: are there trade-offs between leaf growth and accumulation of phenolics?

Abstract: Several plant-herbivore hypotheses are based on the assumption that plants cannot simultaneously allocate resources to growth and defence. We studied seasonal patterns in allocation to growth and putatively defensive compounds by monitoring several chemical and physical traits in the leaves of mountain birch from early June (budburst) to late September (leaf senescence). We found significant seasonal changes in all measured characteristics, both in terms of concentrations (mg g–1) and amounts (mg leaf–1). Changes were very rapid in the spring, slow in the middle of the season, and there was another period of fast changes in the senescing leaves. Co-occurring changes in physical leaf traits and concentrations of several compounds indicated a seasonal decline in foliage suitability for herbivores. Concentrations of protein and free amino acids declined through the growing season whereas individual sugars showed variable seasonal patterns. The seasonal trends of phenolic groups differed drastically: concentrations of soluble proanthocyanidins increased through the season, whereas cell wall-bound proanthocyanidins, gallotannins and flavonoid glycosides declined after an initial increase in young leaves. We failed to find proof that the seasonal accumulation of phenolics would have been seriously compromised by leaf or shoot growth, as assumed by the growth/differentiation balance hypothesis and the protein competition model hypothesis. On the contrary, there was a steady increase in the total amount of phenolics per leaf even during the most active leaf growth.

Relative toxicity of arsenite and arsenate on germination and early seedling growth of rice (oryza sativa l.)

Abstract: Elevated soil arsenic levels resulting from long-term use of arsenic contaminated ground for irrigation in Bangladesh may inhibit seed germination and seedling establishment of rice, the country's main food crop A germination study on rice seeds and a short-term toxicity experiment with different concentrations of arsenite and arsenate on rice seedlings were conducted Percent germination over control decreased significantly with increasing concentrations of arsenite and arsenate Arsenite was found to be more toxic than arsenate for rice seed germination There were varietal differences among the test varieties in response to arsenite and arsenate exposure The performance of the dry season variety Purbachi was the best among the varieties Germination of Purbachi was not inhibited at all up to 4 mg l−1 arsenite and 8 mg l−1 arsenate treatment Root tolerance index (RTI) and relative shoot height (RSH) for rice seedlings decreased with increasing concentrations of arsenite and arsenate Reduction of RTI caused by arsenate was higher than that of arsenite In general, dry season varieties have more tolerance to arsenite or arsenate than the wet season varieties

Cadmium accumulation and buffering of cadmium‐induced stress by arbuscular mycorrhiza in three Pisum sativum L. genotypes

Abstract: The role of arbuscular mycorrhiza in reducing Cd stress was investigated in three genotypes of Pisum sativum L. (cv. Frisson, VIR4788, VIR7128), grown in soil/sand pot cultures in the presence and absence of 2-3 mg kg(-1) bioavailable Cd, and inoculated or not with the arbuscular mycorrhizal fungus Glomus intraradices. Shoot, root and pod biomass were decreased by Cd in non-mycorrhizal plants. The presence of mycorrhiza attenuated the negative effect of Cd so that shoot biomass and activity of photosystem II, based on chlorophyll a fluorescence, were not significantly different between mycorrhizal plants growing in the presence or absence of the heavy metal (HM). Total P concentrations were not significantly different between mycorrhizal and non-mycorrhizal plants treated with Cd. From 20-50-fold more Cd accumulated in roots than in shoots of Cd-treated plants, and overall levels were comparable to other metal-accumulating plants. Genetic variability in Cd accumulation existed between the pea genotypes. Concentration of the HM was lowest in roots of VIR4788 and in pods of VIR4788 and VIR7128. G. intraradices inoculation decreased Cd accumulation in roots and pods of cv. Frisson, whilst high concentrations were maintained in roots and pods of mycorrhizal VIR7128. Shoot concentrations of Cd increased in mycorrhizal cv. Frisson and VIR4788. Sequestration of Cd in root cell walls and/or cytoplasm, measured by EDS/SEM, was comparable between non-mycorrhizal pea genotypes but considerably decreased in mycorrhizal cv. Frisson and VIR7128. Possible mechanisms for mycorrhiza buffering of Cd-induced stress in the pea genotypes are discussed.

Study of the influence of magnetic field on some biological characteristics of zea mais

Abstract: The effect of the static magnetic field of 0,15 Т induction on the maize seeds was studied. The germinating energy and seed germination were detected. The fresh weight and the shoot length were measured. The absorption spectra and the specific electroconductivity of the water extract from seeds were registered. It was detected that the magnetic field stimulated the shoot development and led to the increase of the germinating energy, germination, fresh weight and shoot length. The extinction of the samples treated with a magnetic field increased by about 20 %. The highest values of the treated sample parameters were obtained after 10-min exposure in the magnetic field.

Global and Hormone-Induced Gene Expression Changes during Shoot Development in Arabidopsis

Abstract: A global analysis of gene expression events during shoot development in Arabidopsis was conducted using oligonucleotide array analysis. Shoots can be induced in tissue culture by preincubating root explants on an auxin-rich callus induction medium (CIM) and by transferring explants to a cytokinin-rich shoot induction medium (SIM), during which time explants become committed to shoot formation and ultimately form shoots. Oligonucleotide array data obtained during shoot development from ∼8000 Arabidopsis genes were subjected to principal component analysis, which demonstrated that the major components of variation in gene expression during shoot development can be represented by groups of genes, each group of which is upregulated at only one developmental stage. Two percent to three percent of the ∼8000 Arabidopsis genes monitored in this study were upregulated by fourfold or more at any one stage during shoot development. When upregulated and downregulated genes were categorized by function, it was observed that numerous hormone response genes were upregulated during preincubation on CIM. Groups of genes involved in signaling and/or transcription were induced at or before the time of shoot commitment, and genes that encode components of the photosynthetic apparatus were upregulated later in development before shoot emergence. Primary hormone response genes, such as Aux/IAA genes, were upregulated during preincubation on auxin-rich CIM, and cytokinin-responsive response regulator genes were upregulated during incubation on cytokinin-rich SIM. The expression of ARABIDOPSIS RESPONSE REGULATOR5, a type-A response regulator gene, was upregulated at the time of shoot commitment, and its expression was localized to sites of presumptive shoot formation. Two “hybrid” His kinases involved in cytokinin responses, CRE1, which encodes a cytokinin receptor, and CKI1, a gene that is capable of conferring cytokinin-independent shoot development, were upregulated during incubation on SIM.

The effect of salinity on some physiological parameters in two maize cultivars

Abstract: Summary. In this study, effect of salinity with different osmotic potential on shoot length, total fresh and dry weight, amounts of organic (proline) and inorganic (K + and Na + ) substance of leaf tissue, the Na + /K + ratio, and leaf area, relative water content (RWC) and leaf osmolality in two maize (Zea mays L., var. intendata, C.6127 and DK.623) cultivars which are grown as a second yield in the Southeastern Anatolia Region (SAR) of Turkey, were investigated. Plants were grown for 30 days in the controlled growth room. Salinized culture solutions at different osmotic potential (0, -0.1, -0.3 and -0.5 MPa) prepared by adding varying amounts of NaCl and CaCl 2 to the main culture solution were applied to plants from the beginning of the germination. As a result the shoot length, total fresh and dry weight and the leaf area decreased, amounts of proline Na + , Na + /K + ratio and the leaf osmolality increased, but amounts of K + did not change significantly with increasing stress, and salt stress caused a similar decrease in leaf relative water content in both maize cultivars.

Identification of drought-sensitive beech ecotypes by physiological parameters.

Abstract: Summary • The effects of drought on European beech (Fagus sylvatica) were assessed in a pot experiment under controlled conditions. • Plants from 11 autochthonous provenances originating from regions in Germany, which differed in annual precipitation, were exposed to a 3-wk drought period in a glasshouse after the first stage of shoot growth had been completed. • Drought reduced the water content to 97% of control in leaves and axes and to 92% in the roots. A strong reduction of predawn water potential in roots and shoots, as well as on transpiration rate, was found. In the roots, the effect on water potential was the same for all provenances, but differences were observed in the shoot water potential. Leaf concentrations of abscisic acid (ABA), proline and sucrose increased in the drought-treated plants compared with the controls. • Two extreme clusters from opposite climatic sites were identified by cluster analysis. A drought-sensitive cluster, originating from regions with high annual precipitation, had low water potential and transpiration rates, as well as high concentrations of fructose, ABA and proline after drought. Water potential and transpiration rates were less affected by drought in the other cluster, which comprised two provenances of relatively dry habitats, and concentrations of hexose, ABA and proline were low.

Micropropagation and field evaluation of micropropagated plants of turmeric

Abstract: A protocol was developed for in vitro propagation of turmeric cv `elite' using young vegetative buds from sprouting rhizomes. The shoot buds produced multiple shoots when cultured on MS solid medium supplemented with benzyladenine and 1-naphthalene acetic acid. The effect of various cytokinins on shoot multiplication was studied by culturing the shoot tips on MS liquid medium supplemented with benzyladenine, benzyladenine riboside, kinetin, kinetin riboside, zeatin, 6-γ,γ-dimethylallylaminopurine, adenine, adenine sulfate or metatopolin each at 10 μM in combination with 1-naphthalene acetic acid (1 μM). Significant differences were observed between the treatments. Liquid medium was more favourable than agar medium for shoot multiplication. Among the various concentrations of agar tested, 0.4% and 0.6% were the best and produced the highest number of shoots per explant. Among the different carbohydrates tested, sucrose, fructose, glucose, sugar cubes, maltose, levulose and market sugar were found to be equally effective for shoot multiplication and xylose, rhamnose, lactose and soluble starch were inhibitory. Ninety five percent of the micropropagated plants survived in sterilized soil in paper cups and all of them survived in the field. Among 48 plants, two plants showed variegated leaves on the tillers. The micropropagated plants showed a significant increase in shoot length, number of tillers, number and length of leaves, number of fingers and total fresh rhizome weight per plant when compared with conventionally propagated plants. RAPD analysis of 11 regenerated plants using sixteen 10-mer primers did not show any polymorphism.

Primary and secondary stem growth in arctic shrubs: implications for community response to environmental change

Abstract: Summary 1 Shrubs are among the tundra plants most responsive to environmental change We measured primary and secondary stem growth in a retrospective analysis of ramets of three codominant shrubs (Betula nana, Salix pulchra, and Ledum palustre ssp decumbens) exposed to long-term field treatment with greenhouses and N + P fertilizers at Toolik Lake, Alaska 2 Ramets of Salix had the greatest primary stem growth under control conditions, because of their relatively high branching rate Under fertilization, however, Betula produced much more primary stem growth than the other species, because axillary buds that would have grown as short shoots in control ramets were instead stimulated to produce long shoots (structural branches) There appeared to be a trade-off between allocation to length per stem segment and number of stem segments produced in a given year, for both Betula and Ledum 3 Although secondary growth in stems is the largest component of above-ground net primary production in forests, it is often ignored in shrub-dominated ecosystems We derived an expression for secondary growth in shrubs based on distributions of stem mass and length with age, and allowing for experimentally induced changes in secondary growth rate 4 There was good agreement between measured ramet stem mass and calculated values for all three species, validating our mathematical analysis of secondary growth 5 Fertilization greatly increased the relative rate of secondary growth only in Betula, consistent with observed accumulations of its stem mass in ecosystem-level quadrat harvests Secondary growth of Betula was a major component of ecosystem NPP in fertilized plots and probably contributes significantly to ecosystem carbon storage 6 The increase in its secondary growth enabled Betula to become dominant under fertilization, whereas the inability of older stems of Ledum to respond in this way prevented it from growing into the canopy

Characterization of a lead hyperaccumulator shrub, Sesbania drummondii.

Abstract: Lead phytoextraction can be economically feasible only when the developed systems employ high biomass plants that can accumulate greater than 1% Pb in their shoots. In this study Sesbania drummondii, a leguminous shrub occurring in the wild, was used to demonstrate its capability for greater than 1% Pb accumulation in shoots when grown in a Pb-contaminated nutrient solution. Shoot concentrations of >4% Pb were obtained from Sesbania plants grown on modified Hoagland's solution containing 1 g Pb(NO3)2/L. The accumulation of Pb in the tissue was found to be dependent on the concentration of Pb in the nutrient solution. Addition of EDTA (100 μM) in the medium containing 1 g Pb(NO3)2/L increased uptake by 21%. Lower pH also favored Pb translocation to shoot. Results also indicate the path of Pb transport through root tissues. Scanning electron microscopy revealed the distribution of Pb granules in the cells from epidermis to the central axis, indicating both apoplastic and symplastic modes of transport. Trans...

Allelopathic Effects of Parthenium hysterophorus Extracts on Seed Germination and Seedling Growth of Eragrostis tef

Abstract: The present study was conducted to investigate the allelopathic effects of Parthenium hysterophorus weed on seed germination and seedling growth of tef. Flower, stem, root and leaf aqueous extracts of Parthenium at 0, 1, 5, and 10 % concentrations were applied to determine their effect on tef seed germination and seedling growth under laboratory conditions. Increasing concentrations of aqueous extracts of Parthenium from leaf and flower inhibited seed germination and complete failure of seed germination was recorded when the extract concentration from the leaf part was 10 %. In contrast, aqueous extracts from stem and root had no effect on tef seed germination. Roots appeared more sensitive to allelopathic effect than shoots. Extracts from flower, root and stem had a stimulatory effect on shoot length at all concentration levels, as against an inhibitory effect of leaf extracts. Root extracts at low concentration (1 %) greatly promoted root length but aqueous extracts from leaf and flower inhibited root length.

Effect of osmo- and hydropriming of chickpea seeds on seedling growth and carbohydrate metabolism under water deficit stress

Abstract: Seven-day-old seedlings obtained from seeds primed with mannitol (4%)and water showed three to four fold more growth with respect to root and shootlength in comparison with seedlings obtained from non-primed seeds. Seedlingswere grown under water deficit stress conditions created by 15% polyethyleneglycol (PEG) 6000 in the medium. Priming of chickpea seeds with NaCl and PEGwasnot effective in increasing seedling growth under these water deficit stressconditions. The activities of amylase, invertases (acid and alkaline), sucrosesynthase (SS) and sucrose phosphate synthase (SPS) were higher in shoots ofprimed seedlings. An increase in the activities of SS, and both the acid andalkaline invertases was also observed in roots of primed seedlings. The twofoldincrease in specific activity of sucrose phosphate synthase was observed incotyledons of primed seedlings. The higher amylase activity in shoots of primedseedlings enhanced the rapid hydrolysis of transitory starch of the shootleading to more availability of glucose for shoot growth and this was confirmedby the low level of starch in shoots of primed seedlings.

Developmental events and shoot apical meristem gene expression patterns during shoot development in Arabidopsis thaliana

Abstract: Summary Critical developmental and gene expression profiles were charted during the formation of shoots from root explants in Arabidopsis tissue culture. Shoot organogenesis is a two-step process involving pre-incubation on an auxin-rich callus induction medium (CIM) during which time root explants acquire competence to form shoots during subsequent incubation on a cytokinin-rich shoot induction medium (SIM). At a histological level, the organization of shoot apical meristems (SAMs) appears to occur during incubation on SIM about the time of shoot commitment, i.e. the transition from hormone-dependent to hormone-independent shoot development. Genes involved in SAM formation, such as SHOOTMERISTEMLESS (STM) and CLAVATA1 (CLV1), were upregulated at about the time of shoot commitment, while WUSCHEL (WUS) was upregulated somewhat earlier. Genes required for STM expression, such as CUP-SHAPED COTYLEDON 1 and 2 (CUC1 and 2) were upregulated prior to shoot commitment. Gene expression patterns were determined for two GFP enhancer trap lines with tissue-specific expression in the SAM, including one line reporting on CUC1 expression. CUC1 was generally expressed in callus tissue during early incubation on SIM, but later CUC1 was expressed more locally in presumptive sites of shoot formation. In contrast, the expression pattern of the enhancer trap lines during zygotic embryogenesis was more localized to the presumptive SAM even in early stages of embryogenesis.

In vitro regeneration of Echinacea purpurea from leaf explants

Abstract: Efficient plant regeneration was achieved via organogenesis from callus cultures derived from leaf tissue of Echinacea purpurea. Proliferating shoot cultures were obtained by placing leaf explants on Murashige and Skoog (MS) medium supplemented with 6-benzylaminopurine (BAP) and naphthaleneacetic acid (NAA) combinations. MS medium supplemented with BAP (4.44 μM) and NAA (0.054 μM) was the most effective, providing high shoot regeneration frequencies (100%) associated with a high number of shoots per explant (7.7 shoots/explant). Plantlets were rooted on MS medium alone or in combination with different concentrations of indole-3-butyric acid (IBA), and high rooting and survival was achieved using MS media without plant growth regulators (PGR). All plantlets survived acclimatization producing healthy plants in the greenhouse. This study demonstrated that adventitious shoot regeneration of E. purpurea from leaf explants can be a useful method for the multiplication of this important medicinal plant.

Interactive effects of gibberellic acid (GA3) and salt stress on growth, ion accumulation and photosynthetic capacity of two spring wheat (Triticum aestivum L.) cultivars differing in salt tolerance

Abstract: A sand culture experiment assessed whether gibberellic acid(GA3) could alleviate the adverse effects of salt stress on thegrowth, ion accumulation and photosynthetic capacity of two spring wheatcultivars, Barani-83 (salt sensitive) and SARC-I (salt tolerant).Three-week-oldplants of both cultivars were exposed to 0, 100 and 200 molm−3 NaCl in Hoagland's nutrient solution. Threeweeks after the initiation of salt treatments, half of the plants of eachcultivar were sprayed overall with 100 mg L−1GA3 solution. Plants were harvested 3 weeks after theapplication of GA3. Fresh and dry weights of shoots and roots, plantheight and leaf area were decreased with increasing supply of salt, butgibberellic acid treatment caused a significant ameliorative effect on both thecultivars with respect to these growth attributes. However, GA3caused no significant change in grain yields but increased grain size in boththe cultivars. Saline growth medium caused a marked increase in theconcentrations of Na+ and Cl− in shoots androots of both the lines. However, with the application of GA3accumulation of Na+ and Cl− was enhanced inboth shoots and roots of both wheat lines, but more ions accumulated in saltsensitive Barani-83 than in salt tolerant SARC-1. Net CO2assimilation rate (A) of both wheat lines decreased consistently withincreasingsupply of NaCl, but application of GA3 alleviated the effect of saltstress on this variable in both the cultivars. However, the ameliorative effectof the hormone was more pronounced in Barani-83 than in SARC-1. Althoughwater-use efficiency (A/E = CO2assimilation/transpiration) and intrinsic water use efficiency(A/gs = CO2 assimilation/stomatalconductance) decreased significantly with increasing salt concentration of thegrowth medium in both the cultivars, GA3 was more effective inenhancing both the water-use attributes in Barani-83 than in SARC-1. Overall,GA3 treatment stimulated the vegetative growth of both cultivars ofwheat under salt stress, but it caused a slight reduction in grain yield.GA3 treatment enhanced the accumulation of Na+ andCl− in both shoots and roots of wheat plants under saltstress.It also caused a significant increase in photosynthetic capacity in both linesat the vegetative stage under both saline and non-saline media.