Different Stages Of Plant Growth Research Articles

Determination of the uptake and translocation of nitrogen applied at different growth stages of a melon crop ( Cucumis melo L.) using 15N isotope

In order to establish a rational nitrogen (N) fertilisation and reduce groundwater contamination, a clearer understanding of the N distribution through the growing season and its dynamics inside the plant is crucial. In two successive years, a melon crop ( Cucumis melo L. cv. Sancho) was grown under field conditions to determine the uptake of N fertiliser, applied by means of fertigation at different stages of plant growth, and to follow the translocation of N in the plant using 15N-labelled N. In 2006, two experiments were carried out. In the first experiment, labelled 15N fertiliser was supplied at the female-bloom stage and in the second, at the end of fruit ripening. Labelled 15N fertiliser was made from 15NH 4 15NO 3 (10 at.% 15N) and 9.6 kg N ha −1 were applied in each experiment over 6 days (1.6 kg N ha −1 d −1). In 2007, the 15N treatment consisted of applying 20.4 kg N ha −1 as 15NH 4 15NO 3 (10 at.% 15N) in the middle of fruit growth, over 6 days (3.4 kg N ha −1 d −1). In addition, 93 and 95 kg N ha −1 were supplied daily by fertigation as ammonium nitrate in 2006 and 2007, respectively. The results obtained in 2006 suggest that the uptake of N derived from labelled fertiliser by the above-ground parts of the plants was not affected by the time of fertiliser application. At the female-flowering and fruit-ripening stages, the N content derived from 15N-labelled fertiliser was close to 0.435 g m −2 (about 45% of the N applied), while in the middle of fruit growth it was 1.45 g m −2 (71% of the N applied). The N application time affected the amount of N derived from labelled fertiliser that was translocated to the fruits. When the N was supplied later, the N translocation was lower, ranging between 54% at female flowering and 32% at the end of fruit ripening. Approximately 85% of the N translocated came from the leaf when the N was applied at female flowering or in the middle of fruit growth. This value decreased to 72% when the 15N application was at the end of fruit ripening. The ammonium nitrate became available to the plant between 2 and 2.5 weeks after its application. Although the leaf N uptake varied during the crop cycle, the N absorption rate in the whole plant was linear, suggesting that the melon crop could be fertilised with constant daily N amounts until 2–3 weeks before the last harvest.

Grain yield in wheat as affected by short periods of high temperature, drought and their interaction during pre- and post-anthesis stages

Drought and high temperature are especially considered as key stress factors with high potential impact on crop yield. The aim of this study was to investigate the effect of short periods of high temperature, drought and their combination at different growth stages of plant under controlled conditions. The effects of high temperature and drought on grain yield were additive. However, high temperature increased the degree of water stress and the combined effects of drought and high temperature were much more severe than those of each individual treatment. High temperature and drought applied at post- anthesis shortened duration of maturation, grain filling duration and reduced grain yield, mean grain weight, grain number and thousand-grain weight.

Modeling soil and plant phosphorus within DSSAT

The crop models in the Decision Support System for Agrotechnology Transfer (DSSAT) have served worldwide as a research tool for improving predictions of relationships between soil and plant nitrogen (N) and crop yield. However, without a phosphorus (P) simulation option, the applicability of the DSSAT crop models in P-deficient environments is limited. In this study, a soil–plant P model integrated to DSSAT was described, and results showing the ability of the model to mimic wide differences in maize responses to P in Ghana are presented as preliminary attempts to testing the model on highly weathered soils. The model simulates P transformations between soil inorganic labile, active and stable pools and soil organic microbial and stable pools. Plant growth is limited by P between two concentration thresholds that are species-specific optimum and minimum concentrations of P defined at different stages of plant growth. Phosphorus stress factors are computed to reduce photosynthesis, dry matter accumulation and dry matter partitioning. Testing on two highly weathered soils from Ghana over a wide range of N and P fertilizer application rates indicated that the P model achieved good predictability skill at one site (Kpeve) with a final grain yield root mean squared error (RMSE) of 535 kg ha −1and a final biomass RMSE of 507 kg ha −1. At the other site (Wa), the RMSE was 474 kg ha −1 for final grain yield and 1675 kg ha −1 for final biomass. A local sensitivity analysis indicated that under P-limiting conditions and no P fertilizer application, crop biomass, grain yield, and P uptake could be increased by over 0.10% due to organic P mineralization resulting from a 1% increase in organic carbon. It was also shown that the modeling philosophy that makes P in a root-free zone unavailable to plants resulted in a better agreement of simulated crop biomass and grain yield with field measurements. Because the complex soil P chemistry makes the availability of P to plants extremely variable, testing under a wider range of agro-ecological conditions is needed to complement the initial evaluation presented here, and extend the use of the DSSAT-P model to other P-deficient environments.

Variation in macro-elements and protein contents of roselle (<i>Hibiscus sabdariffa</i> L.) from Niger

Roselle is an important part of the human diet in many countries, particularly in the Sahel zone of West Africa. The leaves of Roselle are consumed as a green vegetable and in sauce. Nevertheless, little attention has been paid to their nutrient composition at different stages of plant growth. Therefore, the experiment was carried out under rainfall conditions from July to September 2006 at the experimental station of the Agrhymet Regional Centre in Niamey (Niger). The contents of Ca, K, Mg, P and protein in leaves of three ecotypes (A3, A7 and A9) were determined at stages I, II and III, corresponding, respectively to vegetative, flowering and mature stages. The experimental design was a randomized complete block with four replicates and one variable (ecotype). For ecotype A7, the protein content of the leaves decreased significantly (p

Inheritance of DNA Methylation in Two Cotton Hybrid Derived from CRI-12

DNA methylation in the form of cytosine methylation is proposed as an evolutionary event, which contributes to genome evolution and plays an important role in maintaining genome integrity and controlling dynamics of gene activity. Hybridization and polyploidization play significant roles in the evolution of higher plants. Compared with animals, cytosine methylation is more abundant in plants, particularly at genomic regions containing transposons and their derivatives. Accumulated evidence had suggested that DNA methylation plays important roles in normal plant development. In different stages of plant growth, the changes in DNA methylation level play an important role in response to variations of its heredity and the environment. Notwithstanding these interesting findings, the causing factors for, and generality of, methylation dynamics in plants, particularly with hybrid formation and trans-generational heritability, remained largely vague. However, there is a paucity of evidence to support any direct link between the epigenetic phenomena of cytosine methylation alteration and gene silencing following hybridization and polyploidization. In this study, MSAP (methylation-sensitive amplified fragment length polymorphism) was used in this study to detect the DNA methylation patterns in the 5′-CCGG sites of two cotton hybrids derived from CRI-12 and their parents for understanding developmental stability and inheritance of cytosine methylation. It was found MSAP ratios, which were the ratios of MSAP type in the two cotton hybrids were 12.41–20.05%, cytosine methylation profiles were variable, from increase to decrease during plant growth and development. Full methylation of internal cytosine (6.90–11.47%) was the dominant in two cotton hybrids. Meanwhile, the MSAP profiles enable the monitoring of inheritance or variation of parental methylation patterns in hybrid progenies. It was found that a great majority (from 96.61% to 98.86%, depending on crosses) of the methylation profiles in cotton inbred lines transmitted to the inter-strain hybrids; however, from 1.14% to 3.39% of the profiles in the hybrids exhibited variation from the expected parental additivity. Both inherited and altered methylation profiles can be divided into distinct groups, and their frequencies are variable among the cross-combinations, and during plant growth and development. Bands in hybrids that appeared in both groups digested by Hpa II-EcoR I and Msp I-EcoR I, which were inherited from either or both of the maternal and paternal parent—this type apparently comprised the greatest majority, as all monomorphic bands belong to this type. In addition, sequencing of differentially methylated fragments and subsequent homology analysis of isolated bands that showed variation in hybrids indicated that diverse sequences were involved, including known-function cellular genes and mobile elements, Such as leucine-rich repeat family protein, PDR-like ABC-transporter, putative oligopeptide transporter, GTP-binding protein, similar to pathogenesis-related protein, DOMON domain-containing protein, putative adenosine phosphosulfate kinase, putative protein, RNA-directed DNA polymerase. The remaining 14 bands showed no homology to the database sequences. These results clearly demonstrated the power of the MSAP technique for large-scale DNA methylation detection in the cotton genome, and the complexity of DNA methylation change during plant growth and development. The different methylation levels may be induced by interspecific hybridization between two cotton hybrids, and indicated a direct relationship between cytosine methylation alteration and gene expression variation.

Growth temperature and plant age influence on nutritional quality of <i>Amaranthus</i> leaves and seed germination capacity<sup>#</sup>

As a leafy vegetable, Amaranthus can be harvested at different stages of plant growth, ranging from young seedlings to the late juvenile stage, but data on the changes in leaf nutritional value with plant age are scanty. The objective of this study was to determine the effect of growth temperature on Amaranthus leaf yield and nutritional quality at different stages of plant growth. Five species, A. hybridus var. cruentus, A. hypochondriacus, A. tricolor, A. thunbergii and A. hybridus were compared for their response to hot (33/27oC), warm (27/21oC) and cool (21/15oC) temperature regimes (day/night) in separate glasshouses. Plants were harvested at 20, 40 and 60 d after sowing and leaf yield, minerals (Ca, P and Fe), total protein content, amino acid (methionine and lysine) content and antioxidant activity (inhibition of linoleic acid oxidation) were determined. Seed yield and germination capacity, during two years of after-ripening, were also determined. Results showed that leaf protein content differed significantly (P The phosphorus content of leaves was not significantly affected by temperature and stage of plant development, and there were also no significant differences between species. However, the amounts of both calcium and iron changed significantly (P leaves increased consistently with plant age and there were significant (P < 0.01) differences between stages of plant development and growth temperature. Warm temperature regimes were most favourable (P < 0.01) for biomass accumulation in all species. Seed production under cool and hot temperatures significantly (P < 0.01) decreased seed germination capacity for all species, but germination improved in response to after-ripening. It is recommended that for greater nutritional benefit, Amaranthus should be grown under warm conditions and younger leaves are preferable.

Phytoremediation of Metal-Contaminated Soil in Temperate Humid Regions of British Columbia, Canada

The suitability of five plant species was studied for phytoextraction and phytostabilisation in a region with temperate maritime climate of coastal British Columbia, Canada. Pot experiments were conducted using Lolium perenne L (perennial rye grass), Festuca rubra L (creeping red fescue), Helianthus annuus L (sunflower), Poa pratensis L (Kentucky bluegrass) and Brassica napus L (rape) in soils treated with three different metal (Cu, Pb, Mn, and Zn) concentrations. The bio-metric characters of plants in soils with multiple-metal contaminations, their metal accumulation characteristics, translocation properties and metal removal were assessed at different stages of plant growth, 90 and 120 DAS (days after sowing). Lolium was found to be suitable for the phytostabilisation of Cu and Pb, Festuca for Mn and Poa for Zn. Metal removal was higher at 120 than at 90 days after sowing, and metals concentrated more in the underground tissues with less translocation to the aboveground parts. Bioconcentration factors indicate that Festuca had the highest accumulation for Cu, Helianthus for Pb and Zn and Poa for Mn.

ROLC strawberry plant adaptability, productivity, and tolerance to soil-borne disease and mycorrhizal interactions

The potential to improve strawberry cultivation was assessed regarding the use the rolC genes from Agrobacterium rhizogenes that can confer higher levels of free cytokinins. Strawberry (cv. Calypso) rolC lines were produced by genetic transformation of Agrobacterium tumefaciens. Yield and fruit quality of the control and transgenic lines were measured under open-field conditions. The effects of the transgenic rolC lines depended on gene copy number: rolC lines with one (Line A) or two gene (Line B) copies showed 30% greater yields than controls, due to 20% more fruit per plant and an increased fruit weight. Line A also differed in terms of the highest fruit quality, due to 10.5% increased soluble solids and 12.7% higher acidity. Moreover, cv. Calypso rolC lines A and B had increased tolerance to greenhouse infection by Phytophthora cactorum. Conversely, for all of these characters, Line F (five rolC copies) was not significantly different from the control line. The same lines were also used to examine their symbiosis with root arbuscular mycorrhizal fungi (AMF) using vital and non-vital staining of roots collected at different stages of plant growth. Control and rolC plants showed similar intensities of AMF infection according to plant phenology and/or physiology. Furthermore, possible horizontal gene transfer of the rolC gene was tested for the AMF spores by PCR, with all AMF samples negative using rolC primers. The use of the rolC gene should be considered for the improvements provided in productivity, fruit quality and disease resistance of cultivated strawberry that show no effects on soil microorganisms.

Phytoremediation and its effect on the mobility of metals in soil: a fractionation study

Studies were conducted to investigate the effect of phytoremediation on the immobilization of Cu, Pb, Mn and Zn in soils at different stages of plant growth. Two multi-metal soil concentrations were examined in pot experiments by growing five different plant species: Lolium perenne L. (perennial rye grass), Festuca rubra L. (creeping red fescue), Helianthus annuus L. (sunflower), Poa pratensis L. (Kentucky bluegrass) and Brassica napus L. (rape) for this study. Selective sequential extraction techniques differentiated the mobile and immobile metal fractions in the soil. Soil-metal conversions due to plant growth appear to follow the order: organic Cu to oxide Cu; oxide Pb to organic Pb; oxide Mn to exchangeable Mn; and exchangeable Zn to oxide Zn. As the growth of plants proceeded from 90 to 120 days after sowing, the relatively immobile fractions such as the oxide and organic fractions dominated in the soils growing Festuca, Lolium and Poa. The oxide fraction increased in soils growing Festuca, the organic fraction in soils growing Lolium and Poa, and the exchangeable fraction in soils growing Helianthus and Brassica. Based on the partitioning of metals in various soil fractions, Lolium, Poa and Festuca are identified as being suitable for the phytostabilization of metals (Cu, Pb, Mn and Zn) in moderately contaminated acid soil.

Genome-wide identification of BURP domain-containing genes in rice reveals a gene family with diverse structures and responses to abiotic stresses

Increasing evidence suggests that a gene family encoding proteins containing BURP domains have diverse functions in plants, but systematic characterization of this gene family have not been reported. In this study, 17 BURP family genes (OsBURP01-17) were identified and analyzed in rice (Oryza sativa L.). These genes have diverse exon-intron structures and distinct organization of putative motifs. Based on the phylogenetic analysis of BURP protein sequences from rice and other plant species, the BURP family was classified into seven subfamilies, including two subfamilies (BURP V and BURP VI) with members from rice only and one subfamily (BURP VII) with members from monocotyledons only. Two BURP gene clusters, belonging to BURP V and BURP VI, were located in the duplicated region on chromosome 5 and 6 of rice, respectively. Transcript level analysis of BURP genes of rice in various tissues and organs revealed different tempo-spatial expression patterns, suggesting that these genes may function at different stages of plant growth and development. Interestingly, all the genes of the BURP VII subfamily were predominantly expressed in flower organs. We also investigated the expression patterns of BURP genes of rice under different stress conditions. The results suggested that, except for two genes (OsBURP01 and OsBURP13), all other members were induced by at least one of the stresses including drought, salt, cold, and abscisic acid treatment. Two genes (OsBURP05 and OsBURP16) were responsive to all the stress treatments and most of the OsBURP genes were responsive to salt stress. Promoter sequence analysis revealed an over-abundance of stress-related cis-elements in the stress-responsive genes. The data presented here provide important clues for elucidating the functions of genes of this family.

Prolyl-4-hydroxylase (AtP4H1) mediates and mimics low oxygen response in Arabidopsis thaliana

Proline hydroxylation is an important phenomenon of a living cell. Prolyl-4-hydroxylases (P4H) responsible for this process have been characterized from animals, and one of its forms, HIF-P4H, is regarded as an oxygen sensor. In plants, P4H has been partially characterized from few species, and one of the Arabidopsis P4H (AtP4H1) has been shown to hydroxylate proline-rich peptides in vitro. In order to study its function in planta, we have overexpressed AtP4H1 in Arabidopsis. The AtP4H1oexp plants showed hypoxia-in-normoxia phenotype with strict requirement for carbon source for its growth, increased root hair, absence of trichome, and reduction in seed size. Genome-wide expression analyses suggest that expression of several genes related to hypoxia as well as plant growth and development are upregulated in AtP4H1oexp lines. Based on our studies on AtP4H1oexp lines, we speculate a direct role of AtP4H1 in hypoxia stress and in different stages of plant growth and development.

Essential Oil Content and Composition of Satureja sahendica Bornm. at Different Stages of Plant Growth

The aerial parts of Satureja sahandica Bornm. were collected in three stages of plant growth (at the beginning of, full and end of flowering stage) from Ghazvin province in the north of Iran. The essential oils were isolated by hydrodistillation from the aerial parts of the plant material. The oils were analyzed by capillary GC and GC/MS. The highest oil yield was obtained at the beginning of flowering (3.30% w/w), then the oil content decreased to 2.28% at full flowering stage and more decreased (1.65%) at the end of flowering. Twenty-three compounds were identified in the oil of S. sahandica at the beginning of flowering with γ-terpinene (42.3%), thymol (34.6%) and p-cymene (11.7%) as main components. Twenty-three constituents were characterized in the oil of full flowering stage with p-cymene (30.2%), thymol (29.6%) and γ-terpinene (27.7%) as major components. Twenty-seven compounds were identified in the oil at the end of flowering with p-cymene (58.1%), thymol (19.3%) and γ-terpinene (9.3%) as main components. The results showed, the percentage of p-cymene was increased in the oil of Satureja sahendica with growth of the plant and during flowering period and the percentage of thymol and γ-terpinene have been reduced. So, harvesting of Satureja sahendica can be commented at the beginning of flowering because of higher oil content and percentage of thymol.

Coal-smoke pollution modifies physio-chemical characteristics of tissues during the ontogeny of Peristrophe bicalyculata

Coal-smoke emissions of a thermal power plant affected the physio-chemical status of Peristrophe bicalyculata (Reth) Nees, as observed at the pre-flowering, flowering and post-flowering stages of plant growth. The nitrate level was raised while nitrate reductase activity, and the soluble protein content of leaf declined heavily at the polluted site during different stages of plant growth, compared to the control. The rate of photosynthesis also decreased under the pollution stress. Sugar level in root, stem and leaves increased with growing age of the plant but was always lower at the polluted site than at the reference site. In roots, the difference was marginal till flowering stage and quite conspicuous afterwards; stems showed a reverse pattern of variation. Sulphur content was higher at the polluted site in all the organs and at each stage of the plant life. The Zn and Fe concentrations were reduced in all plant parts under the pollution stress. Copper content in root was consistently low at the polluted site. In the stem and leaves, however, it was almost equal on both the sites at the pre-flowering stage but showed a wide difference during the later part of plant ontogeny.

Growth, Yield, and Economics of Okra and Amaranth Production Under Irrigation

Small-scale vegetable growers need investment and cost guidelines for irrigation systems in order to evaluate the economics and profitability of growing crops with irrigation. Growth, yield, and economics of producing okra and amaranth under four irrigation methods—basin, drip, furrow, and sprinkler—were evaluated. The experiment was conducted at the Teaching and Research Farm at Obafemi Awolowo University, Ile-Ife, Nigeria, on a sandy loam soil during the dry season. Plant heights and leaf area index were measured at different stages of plant growth; yield was measured at maturity. Fixed and variable costs of all the methods were estimated using results from field experiments and data collected from 50 farms, as well as from the State Agricultural Development Authority. Economic analyses of crop growth under the four methods were carried out. Results indicated that plants receiving drip and sprinkler irrigation had significantly higher yield than furrow and basin for both amaranth (Amaranthus cruentus L.) and okra [Abelmoschus esculentus (L.) Moench]. However, drip irrigation had higher water use efficiency than the sprinkler system for both crops; for okra, water use efficiency with furrow irrigation was significantly higher than that for basin irrigation. Partial budgeting indicated that all systems were profitable. However, basin irrigation had the least cost-benefit ratio and drip had the highest. Economic analyses indicated that a minimum of a 2½- and 3-year period would be needed to pay off fixed assets for drip irrigation for amaranth and okra, respectively. It is recommended that drip irrigation be used for production of amaranth and okra, especially where labor is neither readily available nor cheap.

Zinc-Induced Changes in Growth Characters, Foliar Properties, and Zn-Accumulation Capacity of Pigeon Pea at Different Stages of Plant Growth

ABSTRACT Application of zinc (Zn) [50, 100, 200, 300, and 400 μ g zinc sulfate (ZnSO4)/g of soil] reduced the foliage and the total growth of pigeon pea [Cajanus cajan (Linn.) Huth]. The root-shoot length ratio, varying little with age, was relatively low in the treated plants. Decrease in dry weights of stem and root was more pronounced in the late stages of plant development. The root-shoot dry weight ratio, maximum in the flowering stage, was lower in treated plants than in the control. Number of pods per plant declined, showing a positive correlation with Zn concentration. Net photosynthetic rate, declining with plant age, was significantly low in the treated plants. Density and size of stomata and trichomes, stomatal conductance, intercellular carbon dioxide concentration, quantity of green pigments, nitrate reductase activity, and the nitrate and protein contents in the leaves also declined significantly. Proportion of vascular tissues both in stems and roots increased with plant age with a concomitant reduction of pith and cortex. Under zinc stress, the relative proportion of tissues varied inconsistently. Dimensions of vessel elements and fibers in stems and roots, increasing with the plant age, were always smaller in the treated plants. The vulnerability factor and mesomorphic ratio of treated plants declined, suggesting induction of water stress due to zinc treatments. Accumulation of Zn2 + in different plant parts was considerably high at each developmental stage of the treated plants, and showed a positive correlation with Zn in the soil.

Ramie fibre: part II. Physical fibre properties. A critical appreciation of recent developments

This monograph critically reviews recent research work and developments in physical and related properties of ramie, a long vegetable bast fibre. The properties of the fibre at different stages of plant growth including topography, optical microscopy, electron microscopy, moisture regain, density, strength, tenacity, fineness and mechanical properties as well as thermal, infrared, FTIR and X-ray properties are discussed.

Effects of humic substances derived from organic waste enhancement on the growth and mineral nutrition of maize

A physico-chemical process has been developed to transform and enhance lignocellulosic waste in liquid humic extracts: humic-like substances (HLS). The aim of this study was to determine the effects of HLS on plant physiology in order to consider their agricultural use as organic fertilizers. The effects of HLS were evaluated on maize seed germination, and their impact on growth, development and mineral nutrition was studied on maize plants cultivated under hydroponic conditions. The experimental results showed that HLS do not increase the percentage and rate of germination but enhance the root elongation of seeds thus treated. Positive effects were also observed on the whole plant growth as well as on root, shoot and leaf biomass. These effects can be related to the high water and mineral consumption of plants undergoing this treatment. The high water efficiency indicated that such plants produce more biomass than non-treated plants for the same consumption of the nutrient solution. Furthermore, the use of HLS induced a flowering precocity and modified root development suggesting a possible interaction of HLS with developmental processes. Considering the beneficial effect of HLS on different stages of plant growth, their use may present various scientific and economic advantages. The physico-chemical transformation of sawdust is an interesting way of enhancing organic waste materials.

Step-by-step morpho-physiological responses of Arachis hypogaea L. cv. NC 2 to iron deficiency

Well-aerated and alkaline soils are proven to lack plant-available iron. Fe-efficient plants, however, induce morpho-physiological and biochemical mechanisms of adaptation. These changes in morphology and physiology of the shoot-root systems of peanut (&lt;i&gt;Arachis hypogaea&lt;/i&gt; L. cv. NC 2) plants were studied by cultivating them hydroponically in the nutrient solution containing different levels of Fe&lt;sup&gt;3+&lt;/sup&gt;EDDHA (0.00, 0.125, 0.25, 0.50, 1 and 2 ppm). Three types of chlorosis and regreening (I, II, III) on the shoot system appeared simultaneously with three types of rooting (I, II, III) in different stages of plant growth under Fe-free media. The difference in the regreening processes of plants grown in Fe-free and Fe-treated media indicated that their signaling pathways for Fe localization might be different. The morphological responses were found to correlate to three types of regular and rhythmic pH changes in the nutrient solutions. The sites of pH responses and Fe&lt;sup&gt;3+&lt;/sup&gt; reducing activities in the roots showed dependence on the type of root and shoot morphology.

Stimulation of antioxidant system and lipid peroxidation by abiotic stresses in leaves of Momordica charantia

The purpose of the present work was to evaluate both the antioxidant response system and oxidative stress in leaves from bitter gourd (Momordica charantia L) subjected to NaCl, UV-B and water stresses at three different stages of plant growth: pre-flowering, flowering and post-flowering. Except for peroxidase (POX), all enzyme activities including superoxide dismutase (SOD), catalase (CAT), polyphenol oxidase (PPO), glutathione reductase (GR), as well as concentrations of ascorbate (ASA), hydrogen peroxide (H2O2) and thiobarbituric acid reactive substances (TBARS) exhibited maximum values at the flowering stage under all three stresses. All the enzyme activities, SOD, CAT, POX, PPO, GR and the concentrations of ASA, H2O2 and TBARS were elevated under NaCl and UV-B stresses at all growth stages with the exception of H2O2 concentration at the post-flowering stage under UV-B radiation. Greater quantities of the inorganic ions Na+ and Cl- were accumulated at all growth stages under salt stress. Drought led to decreases in the concentrations of H2O2, ASA and activities of PPO and GR; conversely, it led to elevated concentrations of TBARS and activities of SOD, CAT, POX at all three stages in comparison with control values. The POX activity at the third stage was, however, reduced. The photosynthetic pigments decreased at all stages under all stresses. The chlorophyll stability index decreased under NaCl stress, accelerated only at the post-flowering stage under UV-B radiation and significantly increased at pre- and post-flowering stages under water stress. The protein concentration under NaCl stress decreased except at the pre-flowering stage and under UV-B and water stresses the protein concentration was higher than that of the control and NaCl treatment. It is suggested that M. charantia exhibits a protection mechanism against oxidative damage by maintaining a highly induced antioxidant system under all three stresses.

Effects of N and K Applications on Agronomic Characteristics of Two Iranian and Landrace Rice (Oryza sativa L.) Cultivars

Nutrition elements like nitrogen and potassium are restricting yield performance of rice cultivars and affecting on their characteristics. In order to consider effects of different amount of nitrogen and potassium on yield and chemical compounds of two rice cultivars (Tarrom and Neda which are landrace and improved Iranian genotypes, respectively), current experiment has been undertaken in 2004 and 2005. Four levels of nitrogen fertilizer (0, 50, 100 and 150 kg N ha(-1) from urea source) and four levels of potassium fertilizer (0, 75, 150 and 225 kg K2O ha(-1) from potassium sulfate source) have been applied in a split-factorial based on randomized block design with three replications. Nitrogen fertilizer has been applied in three different stages of plant growth (1/3 in transplanting, 1/3 in tillering and 1/3 in flowering initial stages) and potassium fertilizer has also been applied in two growth stages (1/2 in transplanting and 1/2 in shooting stages). Results indicated that application of nitrogen has increased plant height, number of tiller, length and width of flag leaf, length of panicle, number of grain per panicle, grain yield, amount of dry matter, biological yield, harvest index, leaf potassium, leaf nitrogen, 1000 grain weight and reducing percentage of hallow grain. Also, applied potassium has positive effects on all of above mentioned yield components except harvest index and 1000 grain yield. Neda cultivar was better than Tarrom genotype for most of the measured traits. Interaction of nitrogen and potassium were affected significantly on number of tiller per plant, grain yield, amount of dry matter and biological yield in Neda cultivar and on length of flag leaf, number of grain per panicle, grain yield, amount of dry matter, biological yield, harvest index and 1000 grain yield in Tarrom genotype.