Values Of Control Plants Research Articles

Impact of Drought Stress on Photosynthetic Response of Some Pear Species

To investigate photosynthetic response of some pear (Pyrus spp.) species to drought stress, a pot experiment was conducted using as factorial experiment based on completely randomized design (CRD) with three replication under greenhouse condition. The factors included five pear species including: P. biossieriana, P. communis, P. glabra, P. salicifolia and P. syriaca and three levels of drought stress [(100%, 60% and 30% of field capacity (FC)]. According to the obtained results, different levels of drought stress significantly restricted morphological and physiological responses in all studied species. Increasing drought stress intensity reduced leaf relative water content (RWC), net photosynthetic rate, stomatal conductance, transpiration rate and intercellular carbon dioxide concentration when compared to their values in control plants. However, root/shoot dry weight ratio, specific leaf weight and stomatal density per unit of area were increased. In P. glabra exposed to severe stress (30% of FC), the values of root/shoot dry weigh ratio (0.85 g), specific leaf weight (23 mg cm-2), stomata density per unit of area, relative water content (73%) and net photosynthetic rate (3.9 µmol CO2 m-2 s-1) were significantly higher than the other species. P. syriaca, P. salicifolia, P. biossieriana and P. communis were placed in the next ranks, respectively based on their response to drought. In conclusion, P. glabra is reported as a more effective species in mitigating the adverse effects of drought by boosting its protective mechanisms than the other pear species.

Drought-tolerant Common Bush Bean Physiological Parameters as Indicators to Identify Susceptibility

Bean crops can be displaced to marginal areas or face abiotic stresses such as water deficit. Physiological responses allow the identification of tolerant genotypes and lead to more precise breeding strategies. The objective of this research was to evaluate the physiological (leaf gas exchange properties, leaf water content, and leaf thickness) and biochemical [proline and malondialdehyde (MDA)] responses of five common bush bean (Phaseolus vulgaris L.) cultivars (ICA-Cerinza, ICA-Bachue, NUA35, Bianca, and Bacatá) under a water shortage period by irrigation suspension (15 days) at two different phenological stages [vegetative: 40–55 days after seed emergence (DAE) or reproductive: (50–65 DAE)]. A completely randomized block design was carried out with a factorial arrangement (the phenological stage as the main factor and the cultivars as the secondary factor) for a total of 10 treatments with four repetitions per treatment. Leaf photosynthesis (Pn) showed equal photosynthesis values in control plants of all cultivars (≈20 μmol·m−2·s−1). The water deficit period reduced Pn close to 55% (≈12 μmol·m−2·s−1) at both, vegetative, or reproductive stage in all cases. Similar results were also observed on leaf thickness, with a reduction of ≈10% in water-stressed plants at either vegetative or reproductive stage in all evaluated cultivars. A higher MDA and proline production were observed in plants affected by a 15-day water deficit period, mainly at the vegetative stage. The obtained results suggest that the vegetative stage presented a more negative impact on the evaluated physiological variables in most of the cultivars used. Cultivar Bachue showed lower gas exchange properties affectation and higher proline content, which may indicate that this cultivar can be tolerant to water deficit stress conditions. This study allows suggesting that proline and MDA estimation are simple, fast, and low-cost techniques to screen cultivars to obtain more precise breeding selection in common bean. Finally, common bean cultivar selection through the use of biochemical markers can be complemented by the estimation of leaf gas exchange parameters at different phenological stages.

Effect of Paclobutrazol and NAA on Sex determination and Seed Yield of Medicinal Pumpkin (Cucurbıta pepo L.)

In order to evaluate the effect of plant growth regulators on sex determination and yield, an experiment was conducted by spraying different hormonal combinations on medicinal pumpkin. Experimental treatments were included different concentrations of NAA (25, 75, 100, 125 mg/l), paclobutrazol (50, 100, 200 and 300 mg/l) and combination of growth regulators (NAA 25 mg/l + PBZ 50 mg/l), (NAA 75 mg/l + PBZ 100 mg/l), (NAA 100 mg/l + PBZ 200 mg/l), (NAA 125 mg/l + PBZ 300 mg/l), and control (no application of growth regulators). Growth regulators were applied on the plants by spraying at the –two-leaf and four-leaf stages. Results showed that spraying paclobutrazol and NAA caused increase in number of female flowers, fruits per plant, seeds per fruits, 1000 seed weight and seed yield per hectare, but the number of male flowers and ratio of male to female flowers were decreased compared to their values in control plants. The highest fresh and dried seed yield of pumpkin seed was obtained with 50 mg/l paclobutrazol.

Metabolic features involved in drought stress tolerance mechanisms in peanut nodules and their contribution to biological nitrogen fixation

Legumes belong to the most important crops worldwide. They increase soil fertility due their ability to establish symbiotic associations with soil microorganisms, known as rhizobia, capable of fixing nitrogen from the atmosphere. However, they are frequently exposed to abiotic stress conditions in particular drought. Such adverse conditions impair the biological nitrogen fixation (BNF) and depend largely on the legume. Therefore, two peanut cultivars with contrasting tolerance to drought, namely the more tolerant EC-98 and the sensitive Granoleico, were investigated to elucidate the relative contribution of BNF to the tolerance to drought. The tolerant cultivar EC-98 sustained growth and BNF similar to the control condition despite the reduced water potential and photosynthesis, suggesting the functioning of distinct metabolic pathways that contributed to enhance the tolerance. The biochemical and metabolomics approaches revealed that nodules from the tolerant cultivar accumulated trehalose, proline and gamma-aminobutyric acid (GABA), metabolites with known function in protecting against drought stress. The amide metabolism was severely affected in nodules from the sensitive cultivar Granoleico as revealed by the low content of asparagine and glutamine in the drought stressed plants. The sensitive cultivar upon rehydration was unable to re-establish a metabolism similar to well-watered plants. This was evidenced by the low level of metabolites and, transcripts and specific activities of enzymes from the carbon (sucrose synthase) and nitrogen (glutamine synthetase) metabolism which decreased below the values of control plants. Therefore, the increased content of metabolites with protective functions under drought stress likely is crucial for the full restoration upon rehydration. Smaller changes of drought stress-related metabolites in nodule are another trait that contributes to the effective control of BNF in the tolerant peanut cultivar (EC-98).

Irrigation of Three Wetland Species and a Hyperaccumlating Fern with Arsenic-Laden Solutions: Observations of Growth, Arsenic Uptake, Nutrient Status, and Chlorophyll Content

Engineered wetlands can be an integral part of a treatment strategy for remediating arsenic-contaminated wastewater, wherein, As is removed by adsorption to soil particles, chemical transformation, precipitation, or accumulation by plants. The remediation process could be optimized by choosing plant species that take up As throughout the seasonal growing period. This report details experiments that utilize wetland plant species native to Ohio (Carex stricta, Pycnanthemum virginianum, and Spartina pectinata) that exhibit seasonally related maximal growth rates, plus one hyperaccumulating fern (Pteris vittata) that was used to compare arsenic tolerance. All plants were irrigated with control or As-laden nutrient solutions (either 0, 1.5, or 25 mg As L−1) for 52 d. Biomass, nutrient content, and chlorophyll content were compared between plants treated and control plants (n = 5). At the higher concentration of arsenic (25 mg L−1), plant biomass, leaf area, and total chlorophyll were all lower than values in control plants. A tolerance index, based on total plant biomass at the end of the experiment, indicated C. stricta (0.99) and S. pectinata (0.84) were more tolerant than the other plant species when irrigated with 1.5 mg As L−1. These plant species can be considered as candidates for engineered wetlands.

Differential effects of two strains of Rhizophagus intraradices on dry biomass and essential oil yield and composition in Calamintha nepeta

The aim of this work was to determine the effects of two geographically different strains of Rhizophagus intraradices (M3 and GA5) on the total biomass and essential oil (EO) yield and composition of Calamintha nepeta, with or without phosphorus (P) fertilization, under greenhouse conditions. The plant biomass was not significantly affected by any of the treatments, showing higher values in control plants. Strains had a differential response in their root colonization rates: M3 reduced these parameters while GA5 did not modify them. Both strains affected EO yield in absence of P fertilization: M3 promoted EO yield in C. nepeta plants and GA5 resulted in negative effects. The percentage composition of EO was not significantly modified by either strain or P fertilization. M3 strain could be a potential fungal bioinoculant for production and commercialization of C. nepeta in the aromatic plant market.

Bioremediation of crude oil polluted soil by the white rot fungus, Pleurotus tuberregium (Fr.) Sing.

Bioremediation has become an attractive alternative to physicochemical methods of remediation of polluted sites. White rot fungi (WRF) are increasingly being investigated and used in bioremediation, because of their ability to degrade an extremely diverse range of very persistent or toxic environmental pollutants. The white rot fungus, Pleurotus tuberregium, was examined for its ability to ameliorate crude oil polluted soil. This was inferred from the ability of the polluted soil to support seed germination and seedling growth in Vigna unguiculata, at 0, 7 and 14 days post treatment. Results obtained from the present study showed that bioremediation of soil contaminated with crude oil was possible, especially when the fungus had been allowed to establish and fully colonize the substrate mixed with the soil. There were significant improvements in % germination, plant height and root elongation values of test plants, when seeds were planted 14 days post soil treatment. At 1 to 5% crude oil pollution, % germination values were comparable with the values in control plants in the 14 days treatment, and significantly higher than values obtained in the day 0 treatment. Also, at the highest level of crude oil pollution (15%), there was about 25% improvement in % germination value over the 0 day treatment. This trend of improvement in values was also observed for plant height, root elongation and biomass accumulation as well as decreased total hydrocarbon content.

Diurnal and seasonal osmotic potential changes in Lotus creticus creticus plants grown under saline stress

Lotus creticus creticus plants growing in a greenhouse were exposed to 0, 70 and 140 mM NaCl for 4 months (September–December). Salinity caused a reduction in total dry weight of Lotus plants treated with 140 mM NaCl, whereas no significant effects on growth were observed with 70 mM NaCl. Predawn leaf water potential and predawn leaf osmotic potential showed constant values in control plants during all the experiment, whereas a decrease of both parameters was observed between September and October for the saline treatments. The relative contribution of passive (dehydration) versus active mechanisms (osmotic adjustment) involved in seasonal leaf osmotic potential changes were determined. Seasonal decreases of the osmotic potential at full turgor in the treated plants showed the capacity for osmotic adjustment by accumulation of Na + and Cl −, because the accumulation of organic solutes due to salts was not consistent. In plants treated with 70 mM NaCl, the seasonal changes of the osmotic potential were produced by net solute accumulation, because the dehydration contribution was negligible. In plants treated with 140 mM NaCl, the seasonal changes of the osmotic potential were originated by ions accumulation, but also by tissues dehydration. At the end of the salinization period (December), a possible diurnal adaptation in water relations was also considered. The dehydration was the major mechanism involved in diurnal changes of leaf osmotic potential, and only at the highest salinity level some diurnal osmotic adjustment could be observed. In conclusion, the osmotic adjustment in Lotus might be a beneficial trait when the plants are treated with moderate levels of salinity (70 mM NaCl). At higher salinity (140 mM NaCl), the high absorption and accumulation of ions caused important toxic effects and induced leaf tissue dehydration.

The susceptibility of PS II of Lolium perenne to a sudden fall in air temperature—response of plants grown in elevated CO 2 and/or increased air temperature

The effect of a sudden fall in air temperature from 20 to 5°C on fast kinetics of chlorophyll fluorescence, maximum yield of the photosystem II photochemical reactions (Fv/Fm), quantum yield of the photosystem II electron transport (Φ II), coefficients of photochemical (qP), non-photochemical quenching (qN) was studied in Lolium perenne using a modulated chlorophyll fluorescence technique. Before fluorescence measurement, the plants were cultivated in the treatments simulating the likely future climate characterized with elevated air temperature and CO 2 concentration and combination of both. On fast kinetics curves the risetimes of the I and D points characterizing the redox state of Q A were affected by lowering the air temperature. At 5°C both the I and D points were reached later than at 20°C. Also the I to D risetime was prolonged at 5°C and it was found significantly longer in plants cultivated in ambient +4°C temperature. While a significant difference was found in the area over the rising part of the fluorescence curve between 20 and 5°C, no difference was found in area over the relaxation curve part. Lowering of air temperature to 5°C had no effect on Fv/Fm values in control plants and in the plants cultivated in elevated CO 2 but brought significant decrease in plants cultivated in the ambient +4°C air temperature. Both Φ II and qP decreased with the temperature lowered to 5°C while the values of qN increased. The changes in fluorescence parameters indicated altered functioning of PS II at low temperature. The changes in parameters are discussed as a consequense of decreased enzymatic activity, decreased turnover of plastoquinone pool and photoinhibition.

Response of short-duration pigeonpea to nitrogen application after short-term waterlogging on a Vertisol

Short-duration pigeonpea suffers from waterlogging damage following heavy rainfall at the pre-flowering stage on soils with high clay content, such as Vertisols. Effects of short-term waterlogging (3 d) on shoot and root growth of short-duration pigeonpea grown on a Vertisol field were quantified, and the alleviation of waterlogging damage by top-dressing of nitrogen fertilizer was examined. Reduced leaf chlorophyll, increased senescence and abscission of lower leaves were observed within 3 d of the initiation of waterlogging. Root growth and symbiotic N 2 fixation were also severely impaired. Root distributions of waterlogged plants were shallower than those of the control during the subsequent recovery period because new adventitious roots were formed in the shallow rather than deep soil layer. Yield of waterlogged crops was significantly smaller than the control. Top-dressing of nitrogen at one day after the termination of waterlogging alleviated waterlogging damage either completely or partially. Leaf chlorophyll and shoot dry mass of waterlogged plants were 78 and 84% of the values in control plants immediately after waterlogging but recovered to 92 and 98% of the control values at the pod-filling stage with a top-dressing of 50 kg N ha −1 . Nitrogen application promoted root growth in the shallow soil layers during the first 11 d after application, and in the deeper soil layers during the subsequent 16 d. Total nodule activity was significantly reduced by 100 kg N ha −1 , but increased by 50 kg N ha −1 around one month after the top-dressing. The reduction in seed yield was largely compensated for by 50 kg N ha −1 , because of recovery from waterlogging damage to shoot and root growth involving increased nodule activity.

Metabolic responses of bush bean plants to naphthenate application

A 0.5% aqueous spray of potassium naphthenates was applied to the foliage of 14-day-old plants of bush bean, Phaseolus vulgaris L. cultivar Top Crop, and the plants were then grown under light intensities of 16.1, 10.76, and 5.38 klx at 26 °C for 7, 14, and 21 days. Photosynthesis, dark respiration, and phosphorylase activity were significantly greater (0.05 level) in treated plants at the end of all three growth periods under all light conditions. Significant stimulation of phosphoglycerate kinase developed more slowly under the lower light intensities. The stimulation of nitrate reductase and glutamic–pyruvic transaminase in treated plants reached a significant level between 7 and 14 days after treatment, and subsequently increased. The percentage increases of all the processes, over corresponding values in control plants, were greatest in plants grown at the highest light intensity.

Growth, Composition, and Metabolic Responses of Sugar Beet to Preharvest Application of Maleic Hydrazide1

AbstractMaleic hydrazide, 8 × M−3, was applied to the foliage of mature plants of sugar beet (Beta vulgaris L.). Its effects on growth and various aspects of composition and metabolism were determined 7, 14, and 21 days after treatment. The striking result was a significant curtailment of growth of leaves and an increase in sucrose content of the storage root. Maximum inhibition of leaf growth, 66%, was evident 7 days after treatment. The sucrose content of the roots was significantly larger on all three days of measurement, while protein and total N were considerably less. Higher nitrate and lower nitrite contents paralleled a decrease in the activity of nitrate reductase.Respiration in both leaves and roots was depressed, but the photosynthetic rate was greater by 49%, 21 days after treatment. The activity of nitrate reductase and transaminase in leaf and root fell 40% and 18% below values in control plants by the 21st day following treatment. Invertase activity was significantly reduced. The activities of glucose‐1‐, glucosed‐, and fructose‐6‐phosphatases; phenyl phosphatase; and ATPase were depressed by treatment. On the other hand, the activities of the enzymes of sucrose biosynthesis, UDPG‐pyrophosphorylase, sucrose synthetase, and sucrose phosphate synthetase, were significantly stimulated.The responses suggest that “ripening” may be induced and that the late autumn growth, which often occurs at the expense of stored sucrose, may be considerably reduced by the foliar application of maleic hydrazide 7 to 21 days before the sugar beets are to be dug.