Reduced Shoot Fresh Weight Research Articles

Metal Sulfates and Microbial Food Treatment Alleviate the Oxidative Damage Caused by PEG-Induced Osmotic Stress in Cotton Plants

Background: Drought stress restricts cotton production, which causes a considerable loss of cotton yields worldwide. Plant activators improve crop production and ameliorate abiotic stresses. Thus, the effects of plant activators on the genotype of cotton (Gossypium hirsutum L.) Candia, which is resistant to drought, were investigated.Methods: Plants were treated with the plant activators, and then osmotic stress was initiated by 30% PEG 6000 treatment for 13 days. Antioxidant enzyme activities such as superoxide dismutase (SOD), ascorbate peroxidase (APX), and peroxidase (POX) were measured along with growth, relative water content (RWC), osmotic potential, photosynthetic pigments, ion leakage, proline accumulation, malondialdehyde (MDA) content, and reactive oxygen species (ROS).Results: Osmotic stress reduced shoot fresh weight (FW) and osmotic potential but increased root length of Candia. Activator treatment alleviated these effects. Photosynthetic pigment contents and cell membrane permeability were not affected by osmotic stress and activator treatments; proline accumulation and lipid peroxidation levels were enhanced by osmotic stress, but activators alleviated these increments. Activity bands for the isozymes Mn-SOD1, SOD2, and SOD3, as well as the isozyme Fe-SOD, were found in Candia. Osmotic stress elevated APX activity in Candia leaves, while activator treatment decreased it. POX activity was not affected by osmotic stress, but activator treatment decreased POX activity. Osmotic stress-induced accumulation of ROS was lessened by activator treatment.Conclusion: Plant activator treatment reduced the amount of oxidative damage (ROS buildup and lipid peroxidation) caused by drought stress in the Candia genotype.Keywords: Antioxidant system; Cotton; Gossypium hirsutum L.; Osmotic stress; PEG 6000; Plant activators

Does humic acid foliar application affect growth and nutrient status of water-stressed maize?

Maize (Zea mays L.) is one of the world's most important crops, but its productivity is at high risk as climate change increases the risk of water stress. Therefore, the development of mitigation strategies to combat water stress in agriculture is fundamental to ensure food security. Humic acids are known to have a positive effect on drought tolerance, but data on their efficacy under waterlogging are lacking. This study aimed to elucidate the effect of a new humic acid product, a by-product of Ukrainian bentonite mining, on maize growth and nutrient status under waterlogging. Maize was grown for 9 weeks and three water stress treatments, which were applied for 14 days: waterlogging, alternating waterlogging and drought, and drought. On the day of stress application, the humic acid product (1% v/v) was applied to the leaves. Soil Plant Analysis Development (SPAD) values were recorded during the stress treatments. Plants were harvested after stressing ceased and fresh weight and P and Zn status were analyzed. Drought reduced shoot fresh weight, while it was unaffected under waterlogging. This is in contrast to SPAD readings, which showed a significant decrease over time under submergence, but not under drought. Under alternating stress, although SPAD values declined under waterlogging but stabilized when switched to drought, no growth reduction was apparent. Application of the humic acid product was ineffective in all cases. Although anthocyanin discoloration occurred under waterlogging stress, P deficiency, which is usually the main factor driving anthocyanin formation, was not the reason. Interestingly, Zn concentration decreased under waterlogging but not under the other stresses, which was alleviated by humic acid application. However, no effect of foliar-applied humic acids was observed under alternating and drought stress. It can be concluded that the tested humic acid product has the potential to improve the Zn status of maize under waterlogging.

Mechanistic insights into mitigating Cd stress in plants using typical organic waste fermentation solutions.

Finding practical solutions for utilizing agricultural organic wastes has always been a challenge. To address this, our study investigated the effects and mechanisms of different exogenous organic waste fermentation solutions on alleviating Cd stress in plants using hydroponic experiments. Out of the seven fermentation solutions examined, pea fermentation liquid (T3), chicken manure (T5), molasses (T6), and chitosan oligosaccharide broth (T9) exhibited positive effects. They increased shoot fresh weight by 1.17%, 26.83%, 7.94%, and 15.59%, and root fresh weight by 50.00%, 12.21%, 81.19%, and 19.47%, respectively. Conversely, amino acid mother liquid (T7) and potassium polyaspartate liquid (T8) reduced shoot fresh weight by 34.21% and 24.74%, and root fresh weight by 27.06% and 7.10%, respectively. All organic waste liquids reduced Cd concentration in shoots and roots. Corn fermentation liquid (T4) reduced Cd in shoots from 87.91 to 19.20 mg/kg, while molasses (T6) reduced Cd in roots from 980.94 to 260.47 mg/kg. SEM-EDX results revealed that molasses (T6) effectively repaired Cd damage on root surfaces. In addition, several waste liquids mitigated microelement absorption disturbances. All waste liquids reduced MDA, corn fermentation liquid (T4), chicken manure (T5), molasses (T6), potassium polyaspartate liquid (T8), and chitosan oligosaccharide liquid (T9) significantly decreased H2O2 by 21.6-38.3%. Structural equation model (SEM) and correlation analysis highlighted the importance of root Mg, Cu, and Zn content and CAT activity in relieving Cd stress and promoting plant growth. Overall, molasses (T6) and chicken manure (T5) demonstrated the most beneficial combined effects, while amino acid mother liquid (T7) and chitosan oligosaccharide liquid (T9) should be exercised with caution due to their weaker effects.

Can microplastics threaten plant productivity and fruit quality? Insights from Micro-Tom and Micro-PET/PVC

Solanum lycopersicum L., a crop grown worldwide with a high nutritional value for the human diet, was used to test the impact of microplastics on plant growth, productivity, and fruit quality. Two of the most represented microplastics in soils, polyethylene terephthalate (PET) and polyvinyl chloride (PVC), were tested. Plants were grown in pots with an environmentally realistic concentration of microplastics and, during the whole crop life cycle, photosynthetic parameters, number of flowers and fruits were monitored. At the end of the cultivation, plant biometry and ionome were evaluated, along with fruit production and quality. Both pollutants had negligible effects on shoot traits, with only PVC causing a significant reduction in shoot fresh weight. Despite an apparent low or no toxicity during the vegetative stage, both microplastics decreased the number of fruits and, in the case of PVC, also their fresh weights. The plastic polymer-induced decline in fruit production was coupled with wide variations in fruit ionome, with marked increases in Ni and Cd. By contrast there was a decline in the nutritionally valuable lycopene, total soluble solids, and total phenols. Altogether, our results reveal that microplastics can not only limit crop productivity but also negatively impact fruit quality and enhance the concentration of food safety hazards, thus raising concerns for their potential health risks for humans.

Leaf extract of neem (Azadirachta indica Adr. Juss.) modulates morphological and biochemical characteristics in maize (Zea mays L.) under water deficit stress

Foliar spray of neem (Azadirachta indica Adr. Juss.) leaf extract was exogenously applied at pre-flowering stage to examine the changes in growth and physio-biochemical characteristics of two maize cultivars (Sultan and Sadaf) under different water regimes (100%, 75% and 60% field capacity). Water deficit conditions significantly reduced shoot fresh weight (SFW), shoot dry weight (SDW), root fresh weight (RFW), root dry weight (RDW), shoot length, root length, chlorophyll b, total soluble proteins and free proline, but it significantly increased ascorbic acid (AsA) and total phenolics in both maize cultivars. Foliar-applied leaf neem extract significantly improved SFW, SDW, RFW, RDW, shoot length, chlorophyll b and ascorbic acid concentrations, but it significantly minimized hydrogen peroxide (H2O2) contents. Application of 1.0% neem extract was effective in improving chlorophyll b and AsA contents, whereas 2.0% neem extract was beneficial for total soluble proteins and MDA contents. Of both maize cultivars, cv. Sultan was found to be drought sensitive and cv. Sadaf as drought tolerant. Exogenous application of leaf neem extract was suggested to be effective in enhancing drought stress tolerance in maize by improving plant growth and oxidative defense system.

Herbicide selection for controlling Tahitian bridal veil (Gibasis pellucida)

AbstractTahitian bridal veil [Gibasis pellucida (M. Martens & Galeotti) D.R. Hunt], a Central and South America native plant that is often confused with another more well-known invasive plant, small leaf spiderwort (Tradescantia fluminensis Vell.), has become invasive in natural areas throughout Florida. However, very little is known regarding herbicide control or other methods. To begin the process of developing herbicide recommendations for land managers who are working to control G. pellucida, multiple postemergence herbicides were screened for efficacy in a shaded greenhouse to determine active ingredients and/or combinations that warrant further investigation under field conditions. Nine different herbicides or combinations, including glyphosate, triclopyr acid, 2,4-D + triclopyr, aminopyralid, 2,4-D, triclopyr amine, metsulfuron-methyl, fluroxypyr, and glufosinate, were applied at standard label rates and compared with a nontreated control group. Visual control ratings were taken at 2, 4, and 8 wk after treatment (WAT), and shoot dry weights were determined at trial conclusion (8 WAT). Data showed glufosinate and triclopyr (acid and amine) provided the highest level of control, as evidenced by control ratings (100% or complete control) and shoot fresh weight reduction, followed by 2,4-D + triclopyr (∼70%) and fluroxypyr (∼50% control). Metsulfuron-methyl and 2,4-D provided the lowest level of control, with results similar to those for nontreated plants on most evaluation dates.

Recovery from Salinity and Drought Stress in the Perennial Sarcocornia fruticosa vs. the Annual Salicornia europaea and S. veneta.

Current agricultural problems, such as the decline of freshwater and fertile land, foster saline agriculture development. Salicornia and Sarcocornia species, with a long history of human consumption, are ideal models for developing halophyte crops. A greenhouse experiment was set up to compare the response of the perennial Sarcocornia fruticosa and the two annual Salicornia europaea and S. veneta to 30 days of salt stress (watering with 700 mM NaCl) and water deficit (complete withholding of irrigation) separate treatments, followed by 15 days of recovery. The three species showed high tolerance to salt stress, based on the accumulation of ions (Na+, Cl−, Ca2+) in the shoots and the synthesis of organic osmolytes. These defence mechanisms were partly constitutive, as active ion transport to the shoots and high levels of glycine betaine were also observed in non-stressed plants. The three halophytes were sensitive to water stress, albeit S. fruticosa to a lesser extent. In fact, S. fruticosa showed a lower reduction in shoot fresh weight than S. europaea or S. veneta, no degradation of photosynthetic pigments, a significant increase in glycine betaine contents, and full recovery after the water stress treatment. The observed differences could be due to a better adaptation of S. fruticosa to a drier natural habitat, as compared to the two Salicornia species. However, a more gradual stress-induced senescence in the perennial S. fruticosa may contribute to greater drought tolerance in this species.

Nitrate-responsive NIN-like protein transcription factors perform unique and redundant roles in Arabidopsis.

Upon sensing nitrate, NODULE INCEPTION (NIN)-like protein (NLP) transcription factors alter gene expression to promote nitrate uptake and utilization. Of the nine NLPs in Arabidopsis, the physiological roles of only three NLPs (NLP6-NLP8) have been characterized to date. To evaluate the unique and redundant roles of Arabidopsis NLPs, we assessed the phenotypes of single and higher order nlp mutants. Unlike other nlp single mutants, nlp2 and nlp7 single mutants showed a reduction in shoot fresh weight when grown in the presence of nitrate as the sole nitrogen source, indicating that NLP2, like NLP7, plays a major role in vegetative growth. Interestingly, the growth defect of nlp7 recovered upon the supply of ammonium or glutamine, whereas that of nlp2 did not. Furthermore, complementation assays using chimeric constructs revealed that the coding sequence, but not the promoter region, of NLP genes was responsible for the differences between nlp2 and nlp7 single mutant phenotypes, suggesting differences in protein function. Importantly, nitrate utilization was almost completely abolished in the nlp septuple mutant (nlp2 nlp4 nlp5 nlp6 nlp7 nlp8 nlp9), suggesting that NLPs other than NLP2 and NLP7 also assist in the regulation of nitrate-inducible gene expression and nitrate-dependent promotion of vegetative growth in Arabidopsis.

Differential Morphophysiological, Biochemical, and Molecular Responses of Maize Hybrids to Salinity and Alkalinity Stresses

Salinity and alkalinity stresses are common in arid and semiarid climates. Both these stresses not only retard crop growth but also cause a severe reduction in yields. The present experiment was performed to investigate the morphological, physiological, biochemical, and genetic responses of two maize hybrids (FH-1231 and DK-6714) to salinity and alkalinity stresses. The treatments were comprised of salt stress (NaCl:Na2SO4 at a 9:1 ratio), alkaline stress (NaHCO3:Na2CO3 at a 9:1 ratio), and an unstressed control. The results indicated that salinity and alkalinity significantly reduced shoot fresh weight by 50% and 70%, root fresh weight by 38% and 50%, root dry weight by 69% and 93%, seedling length by 18% and 30%, number of leaves by 27% and 39%, and maximum leaf width by 17% and 24%, respectively, across the two hybrids compared with control, indicating that alkalinity had a greater effect than salinity. Likewise, both the stresses, particularly alkalinity, significantly decreased K+ ion accumulation and chlorophyll content and increased the lipid peroxidation rate, sodium (Na+) concentration, the hydrogen peroxide (H2O2) level, and the activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX). Salinity and alkalinity stresses also induced the expression levels of antioxidant genes (SOD, CAT, POD, APX); however, salinity showed less effect than alkalinity stress. Similarly, hybrid DK-6714 performed comparatively better than FH-1231 with regard to seedling growth, antioxidant activities, and biochemical attributes under stress conditions. Thus, DK-6714 is recommended as a suitable hybrid for soils affected with salt-alkalization.

Physiological responses of Pea plants to treatment with synthetic auxins and auxin-type herbicide

The effect of exogenously applied 2,4-D (2,4-dichlorophenoxyacetic acid) on growth and antioxidant defence of pea plants, preliminary treated with two synthetic auxin compounds 1-[2-chloroethoxycarbonyl-methyl]-4-naphthalenesulfonic acid calcium salt (TA-12) and 1-[2-dimethylaminoethoxycarbonylmethyl]naphthalene chlormethylate (TA-14) was examined. All chemicals were applied by foliar spraying. Applied alone, TA-12 and TA-14 had no significant effects, but they modulated the 2,4-D induced changes on most investigated biochemical parameters. The shoot fresh weight reduction caused by 2,4-D was partially overcome by the use of TAs. The use of TAs partially overcame the shoot fresh weight reduction induced by 2,4-D. Apart from this, no significant changes were observed in the other biometric parameters. Treatment with 2,4-D did not enhance lipid peroxidation, and hydrogen peroxide content was slightly increased. These data indicate that treatment with 2,4-D did not cause severe oxidative stress, which is also confirmed by the results of the antioxidant defence system. The application of 2,4-D provoked mild accumulation of thiol-containing compounds, free proline and phenolic compounds and increased the antioxidant enzyme activities (GST, SOD, CAT, POD and GR) to a moderate degree. Pretreatment with TAs noticeably decreased the non-enzymatic antioxidants (free proline, total phenolics and total low-molecular thiols) compared to plants treated with 2,4-D only. Except for GR, TAs pretreatment returned the enzyme activities to levels close to the controls. Based on the results obtained, we suggest that the application of both synthetic auxins could modulate 2,4-D herbicide effects.

Effects of constant versus fluctuating red–blue LED radiation on yield and quality of hydroponic purple-leaf lettuce

This study investigated the effects of constant light and alternating relatively high-intensity (500 µmol m−2 s−1) and low-intensity (150 µmol m−2 s−1) red–blue LEDs (4R:1B) on the biomass production and quality of hydroponic purple-leaf lettuce (Lactuca sativa L. cv. ‘Zishan’) in an environmentally controlled plant factory. Four treatments were set up to separate 1 h of high light into four different alternating frequencies in a 24-h light−dark cycle (16/8 h): one time (A1), three times (A3), six times (A6), and twelve times (A12). In addition, one constant light treatment with the same daily light integral (DLI, 9.8 mol m−2 per day) as other treatments was set as the control (CK, 170 µmol m−2 s−1). The results indicated that A6 significantly reduced shoot fresh weight and increased the root–shoot ratio of lettuce compared with CK, but there was no significant difference among other treatments. Alternating light treatments did not promote the accumulation of soluble sugar, soluble protein, and phenolic substances compared with CK. Meanwhile, A12 significantly promoted the accumulation of total ascorbate (TA) in lettuce leaves compared with other treatments but decreased ascorbate/TA ratio. Above all, under the same DLI condition, alternating high and low light did not have obvious positive effects on biomass production and the accumulation of nutrient substance in lettuce under constant light was better than that under alternating light. Therefore, compared with the fluctuating radiation with the same DLI, constant radiation is a better choice for lettuce production.

The First Case of Glyphosate Resistance in Johnsongrass (Sorghum halepense (L.) Pers.) in Europe.

Six Johnsongrass populations suspected of being glyphosate resistant were collected from railways and freeways near Cordoba (SW Spain), where glyphosate is the main weed control tool. The 50% reduction in shoot fresh weight (GR50) values obtained for these six populations ranged from 550.4 to 1169 g ae ha−1, which were 4.2 to 9 times greater than the value obtained for the susceptible population. Glyphosate was equally metabolized to the same extent in both resistant and susceptible populations, with no significant differences in either 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) inhibition or basal activity. No amino acid substitutions were observed in any of the resistant populations. Slight but significant differences in glyphosate penetration were observed among some but not all of the resistant populations and for the times of incubation assayed, although these differences were not considered further. The proposed primary mechanism of resistance in these six glyphosate-resistant Johnsongrass populations is reduced herbicide translocation, because the amount of glyphosate that translocated from treated leaves to shoots and roots in the susceptible population was double that observed in the resistant populations. As glyphosate multiple resistance due to more than one mechanism is not uncommon, this is the first time that glyphosate-resistant Johnsongrass populations have been fully described for all known mechanisms.

Gene Flow from Transgenic PPO-inhibiting Herbicide-resistant Rice to Weedy Rice, and Agronomic Performance by Their Hybrids

Hybridization of transgenic crops with their weedy relatives may spread transgenes into weedy populations and alter the ecological fitness of such hybrids. Our study objective was to quantify the rate of gene flow from herbicide-resistant transgenic rice to weedy rice and compare the performance of hybrids between them over several generations. The transgenic plants used in these experiments are resistant to protoporphyrinogen IX oxidase (PPO)-inhibiting herbicides such as oxyfluorfen, oxadiazon, and butafenacil. The rate of gene flow from those plants to five weedy accessions ranged from 0.025% to 0.139%. The F1 hybrids that resulted from gene flow from transgenic to weedy rice and subsequent F2 progeny were shorter than the weedy parents but produced significantly more and heavier grains. The F3 progeny resulting from gene flow were resistant to oxyfluorfen, which indicated that the gene associated with PPO-inhibiting herbicide resistance is dominantly inherited. The GR50 values (dose required for 50% shoot fresh weight reduction) for F3 progeny were > 69-fold greater than for the weedy rice. These results suggest that transgenes that could escape from PPO-inhibiting herbicide-resistant rice and be transferred to weedy rice might persist and disperse into weedy populations over several generations due to herbicide resistance and improved reproductive traits in the hybrids.

Effects of biochar mixtures with pine-bark based substrates on growth and development of horticultural crops

This study investigates the potential of using biochar as a substrate component to replace pine bark (PB) to produce horticultural crops in containers. Biochar was incorporated in PB at 0, 20, 40, 60, 80 and 100% (by volume) to grow chrysanthemum, tomato, lettuce and basil plants in containers. The responses of plant growth to the percentage of biochar combined in PB mixtures varied among the different crops. Chrysanthemum plants grown in PB mixtures with 80% and 100% biochar had significant higher shoot fresh weight (FW) and dry weight (DW) than plants grown in PB alone, while the same treatments resulted in reduced shoot FW, DW, growth index measured at 19 and 33 days after transplanting and root rating of tomato plants. Growing lettuce plants in 100% biochar reduced the FW of the second crop compared to plants grown in PB substrates supplemented with 0, 20, 40, 60, and 80% biochar. For basil, although biochar alone caused lower root rating, it did not adversely influence the fresh basil yield. Generally, no negative effect on plant growth was observed in PB mixes with biochar as high as 60%, which is probably the outcome of similar physical properties of the biochar to the commonly used PB.

Effects of nickel toxicity on morphological and physiological aspects of osmoregulation in Typha domingensis (Typhaceae) populations

The present work examined morphological and physiological aspects of osmoregulation in some differently adapted populations of Typha domingensis. Six populations of T. domingensis were grown in waterlogged conditions under four levels of nickel (0, 50, 100 and 1500 mg/kg of Ni). The Ni tolerance was explored on the basis of different characteristics of shoots. Along with the increasing level of Ni stress, all populations showed an increment of proline and glycinebetaine content, low photosynthetic and transpiration rates and decreased chlorophyll content. Analyzed morphological parameters revealed possible adaptations to deal with Ni stress. The less tolerant Sahianwala population produced more aerenchyma, less accumulation of osmolytes and reduced shoot fresh weight under Ni stress than the tolerant ones. Our results suggested that T. domingensis has the capacity to survive under Ni stress and could be used for the absorption of toxic metal ions from industrially polluted water.

Polythene Mulch and Irrigation for Mitigation of Salinity Effects on Maize (<i>Zea mays</i> L.)

A pot experiment was conducted at the net house of Patuakhali Science and Technology University during rabi season 2014-15 to estimate the contribution of polythene mulch and irrigation on reducing of salinity effect on maize (Zea mays L.). The experiment was laid out in a three factors randomized complete block design with three replications. The factors were salinity (two levels: without and 5 dS/m salinity), mulch (two levels: without and with polythene mulch) and irrigation (three levels: 125, 250 and 500 ml water/irrigation). BARI hybrid maize-7 was the test crop. Every pot received the same amount of fertilizer nutrients. Crops were harvested at tassel initiation stage. Mulch increased soil temperature by 2 to 4.5°C (with average of 3.1°C) over without mulch. In without mulch condition, salinity reduced shoot fresh and dry, and root fresh and dry weight by 28.3, 10.3, 39.4 and 30.6%, respectively. In with mulch condition, however, these reductions were 1.0, 7.2, 12.3 and 12.1 %, respectively. Polythene mulch reduced salinity induced reduction of the above parameters by 96.5, 30.1, 68.8 and 60.5 %, respectively. Under 125, 250 and 500 ml water/irrigation treatment, salinity reduced shoot fresh weight by 14.2, 19.3 and 6.7 %, respectively; shoot dry weight by 15.4, 6.6 and 5.0 %, respectively; and root fresh weight by 27.5, 20 and 11.6 %, respectively. Thus, the effect of salinity in maize was gradually decreased with the increasing amounts of irrigation water. Soil salinity reduced phosphorus and increased sulphur content in maize plants.The Agriculturists 2016; 14(2) 01-13

Combined use of plant extracts and arbuscular mycorrhizal fungi to reduce root-knot nematode damage in tomato

The effects of mycorrhization by Funneliformis mosseae alone and combined with soil applications of plant extracts from garlic, neem, quassia, and thyme on the damage caused by Meloidogyne incognita in tomato were studied in pot experiments under greenhouse conditions. The nematode reduced shoot fresh weight of tomato by 15% compared with that of nematode-free plants. Nutrient and water stress in M. incognita-infested tomato were detected by measuring the leaf chlorophyll content and canopy temperature, as early as 21 days after nematode inoculation. Mycorrhization by F. mosseae offset the damage caused by the nematode with a general positive effect on plant growth, representing a 17% increase over non-mycorrhized plants. Nematode densities were reduced by garlic, neem, and thyme extracts. Several interactions between treatments proved positive or negative for tomato plant growth, mycorrhization, and nematode reproduction. The most favourable treatment for nematode suppression was a combination of mycorrhization by F. mosseae and application of garlic extract, which increased plant growth by 52%, reduced root galling by 50% and lowered the final nematode population by 51%, when compared to nematode-infested non-treated plants. Neem and thyme extracts showed a negative interaction with F. mosseae, reducing mycorrhization frequency.

Resistance to Fusarium wilt in common bean

In breeding programs, understanding the potential of parents should be a way to spend significantly less time and costs to obtain new cultivars. For this, the objective of this study was to estimate the general and specific combining ability of parents aiming common bean breeding for resistance to Fusarium wilt (FW) based on disease severity and reduction in plant growth. Eight common bean genotypes were crossed in a 3 x 5 partial diallel mating scheme to obtain F1 hybrids. The parents and their 15 F1 hybrids were evaluated for severity of Fusarium wilt, area under the disease progress curve, percentage of plant height reduction and plant shoot fresh weight reduction and grain yield. The resistance of common bean to FW is controlled by a few dominant genes. The reduction in plant growth is controlled by a different set of genes that can increase the selection efficiency of parents for common bean breeding.

Persistence of pendimethalin residues in Swiss chard

The aim of this study was to determine the persistence of pendimethalin and its impact on Swiss chard, as the succeeding crop in the crop rotation, using the bioassay method, by means of the morphological parameters measurement. In applying the tested concentrations of pendimethalin from 0.2475 to 3.96 ppm, the inhibition of certain measured parameters of the Swiss chard tested plants was demonstrated: root growth suppression in the range of 3.91 to 55.47 %, root fresh weight reduction from 5.56 to 55.56 %, reduction of shoot fresh weight from 2.2 to 44.35 % and the reduction of fresh weight of the whole plant in the range of 2.5 to 46.17 %. Inhibition of the fresh root weight a the most sensitive parameter in relation to the applied rates of the herbicide, was demonstrated, while the shoot fresh weight is a parameter that was not sensitive enough. Significant growth inhibition of all measured parameters was observed at pendimethalin concentrations above 0.99 ppm.

Morphological and Physiological Plant Responses to Drought Stress inThymus citriodorus

Water availability is considered as a determinant factor that affects plant growth. The commercial medicinal values of an aromatic plant rely on the presence of secondary metabolites that are affected under water shortage. Two-year-oldThymus citriodorusplants were subjected to different polyethylene glycol (PEG-6000) levels (0, 2%, and 4%) under greenhouse condition. PEG treatment lasted for 15 days. Thyme plant showed a morphological drought avoidance mechanism by maintaining the root system development through shoot fresh weight reduction resulting in promoted root absorption capacity and sustained plant growth. Moreover, stressed plants were able to maintain water use efficiency and root : shoot ratio suggesting a strong relation between root water uptake and water use saving strategies. Furthermore, thyme plants reduced tissue dehydration through stomatal closure and improved root water uptake. Content of volatile oil constituents of geraniol and diisobutyl phthalate increased upon drought stress while pseudophytol was reduced. Unexpectedly, thymol was not reported as a main oil element under either control or mild stress condition, while it was increased upon high drought stress in measure of 4.4%. Finally, carvacrol significantly accumulated under high drought stress (+31.7%) as compared to control plants.