Increased Plant Dry Weight Research Articles

Alleviation of drought stress by silicon supplementation in pistachio (Pistacia vera L.) plants

ABSTRACT The effect of silicon (Si) supplementation (0.35 g Na2SiO3 kg-1 soil, 2.73 mmol Si kg-1 soil) was studied in drought-stressed pistachio (Pistacia vera L. ‘Ahmadaghaii’) plants under field conditions. Silicon treatment significantly increased plant dry weight and relative water content under drought stress. The application of Si for drought-stressed plants improved the maximum quantum yield of PSII. A reduction in the net assimilation rate due to drought stress was alleviated by Si application, accompanied by an increase in stomatal conductance. Silicon treatment resulted in higher catalase and superoxide dismutase activities and lower lipid peroxidation in the leaves of drought-stressed plants. The results suggest that supplementation of water-deficient pistachio plants with Si alleviates the adverse effects of drought due to its enhancement of photochemical efficiency and photosynthetic gas exchange, as well as an activation of the antioxidant defence capacity in this species.

USING PSEUDOMONAS SPP. AND ARBUSCULAR MYCORRHIZAL FUNGI TO ALLEVIATE THE STRESS OF ZINC POLLUTION BY CORN (ZEA MAYS L.) PLANT

The objective was to test the single and combined use of Pseudomonas spp. and Glomus versiforme on the stress of high zinc (Zn) concentration in soil on corn growth as such data are little. Accordingly, in a greenhouse research work the effects of Zn concentrations (control, 100, 200 and 300 mg kg −1 ) and the microbial treatment (control, Pseudomonas spp. and G. versiforme) were tested on corn (single cross 704) growth. Almost three months after planting, plants were harvested. Plant dry weight and Zn uptake were determined. Zn significantly (P = 0.01) affected different measured parameters. The microbes increased plant dry weight related to the control treatment and the highest increase was related to the bacterial application (1.28 times higher). Both bacteria and mycorrhizal fungi and their combined use decreased Zn concentration in plant. The right combination of soil microbes can efficiently affect the process of bioremediation with respect to plant properties.

Relationships between relative growth rate and its components across 11 submersed macrophytes

The relationships between relative growth rate and its components across 11 submersed macrophytes were examined in a short-term experimental study. Plants were grown in identical conditions in pots that were submersed in tanks. The average values for relative growth rate ranged from 17.4 to 94.5 mg g−1 d−1. The net assimilation rate, based on the increase in plant dry weight per unit leaf area in a fixed time, varied fivefold among species and showed a strong, positive correlation with relative growth rate. The leaf area ratio, leaf mass ratio, and specific leaf area were not significantly correlated with the relative growth rate, although these parameters were important in the adaptive responses of macrophytes to environmental stress. These results suggest that the physiological components (net assimilation rate) would be the main determinant of relative growth rate in submersed macrophytes, which highlights the importance of net assimilation rate in explaining differences in macrophyte species performance in freshwater habitat.

Effectiveness of Rhizosphere Bacteria for Control of Root Rot Disease and Improving Plant Growth of Wheat (<i>Triticum </i><i>a</i><i>estivum</i> L)

Pathogenic fungus Rhizoctonia solani causes root rot disease in wheat leading to collapsing of the aerial part of the plant. To characterize antagonistic bacteria, one hundred and thirty bacterial isolates were obtained from the rhizosphere soil of wheat and these rhizobacterial isolates alongwith 72 reference strains were screened for their antagonistic interactions against R. solani under cultural conditions. Sixteen bacterial isolates inhibited the growth of R. solani and growth inhibition zone varied from 6-15 mm by different rhizobacterial isolates. Two isolates WPS3 and WPS90 caused maximum growth inhibition of the fungi. Growth inhibiton of the pathogenic fungi was also observed using culture filterates of antagonistic rhizobacterial isolates. The protein estimation of the culture filterates showed that the amount of protein excreted by different rhizobacterial isolates varied from 3.6 to 33.0 mg ml -1 of the supernatant. The loss of antagonistic activity after treatment with proteinase K and high temperature treatment indicated that excreted proteins are responsible for the antagonism. Pot house studies showed that inoculation of R. solani in wheat caused 85-90% root rot disease incidence at 60 to 90 days of plant growth. The single inoculation of rhizobacterial isolate WPS3 resulted in 131% increase of plant dry weight as compared to uninoculated control plants. The coinoculation of isolate WPS3 with R. solani enhanced 115% plant dry weight whereas coinoculation of Pseudomonas isolate WPS90 caused 98% increase in plant dry weight in comparison to control uninoculated plants at 90 days of plant growth. Coinoculation of Pseudomonas isolates WPS3 and WPS90 with R. solani also caused 88.9 and 66.7% disease control, respectively at 90 days of plant growth. Thus, Pseudomonas isolate WPS3 could be further ex- ploited for plant growth improvement under field conditions.

Effects of Organic and Inorganic Nutrient Sources on the Growth, Total Chlorophyll and Yield of Three Bambara Groundnut Landraces in the Coastal Region of Cameroon

Growth and yield parameters of bambara groundnut [Vigna subterranea L. Verdc. landraces: White Seed Coat (WSC), Black Seed Coat (BSC) and Light Red Seed Coat (RSC)] were evaluated under organic and inorganic fertilization in order to determine the field performance, for the improvement of smallholder agriculture in Cameroon. Four fertilizer application rates (0, 3, 6 and 12 t ha-1) of Water Lettuce (WL) and Poultry Manure (PM) and four fertilization rates (0, 100, 150 and 200 kg ha-1) of N, P and K were used in a randomized complete block design experiment with four replications. Application of WL or PM at 12 t ha-1 significantly (p<0.001) increased leaf water content, plant dry weight and total chlorophyll content in RSC landrace. Application of PM at 12 t ha-1 increased significantly (p<0.001) the number of pods per plant, the number of seeds per pods, the 1000 grain weight, the grain yield and the pod yield in RSC landrace. Significant (p<0.001) increase in plant dry weight was observed in all landraces at 100 kg ha-1 N, P or K fertilization. The fertilization rates above 100 kg ha-1 N, P or K led to a decline in yield in all the bambara groundnut landraces compared to the optimum 100 kg ha-1 N, P or K fertilization. RSC landrace showed better growth and yield than WSC and BSC landraces revealing a greater response of this cultivar to fertilization.

Effects of AM Inoculation and Organic Amendment, Alone or in Combination, on Growth, P Nutrition, and Heavy-Metal Uptake of Tobacco in Pb-Cd-Contaminated Soil

As toxic pollutants commonly found in tobacco (Nicotiana tabacum L.) products, lead (Pb) and cadmium (Cd) can enter the human body via smoking and thus pose a potential health risk to smokers. We conducted a greenhouse experiment to study the effects of arbuscular mycorrhizal (AM) inoculation with Glomus intraradices BEG 141 and organic amendment with cattle manure, alone or in combination, on the growth, P nutrition, and heavy-metal uptake by tobacco plants grown in soil to which was added Pb-Cd at 0/0, 350/1, 500/10, and 1,000/100 mg kg−1, respectively. In general, AM colonization and plant growth were greatly reduced by Pb-Cd contamination, whereas organic amendment alleviated Pb-Cd stress and showed some beneficial effects on AM symbiosis and some soil parameters. AM inoculation, alone or in combination with organic amendment, increased plant dry weights and improved P nutrition significantly at all Pb-Cd addition levels, and, in most cases, it decreased Pb and Cd concentrations in tobacco plants and DTPA-extractable concentrations in soil. AM inoculation increased total glomalin-related soil protein (GRSP) concentrations in soil to which Pb-Cd was added. The higher soil pH and GRSP contents and the lower DTPA-extractable Pb and Cd concentrations contributed by AM inoculation and/or organic amendment may be contributing factors that lead to higher growth promotion and lower metal toxicity and uptake by plants. Our findings suggest that AM inoculation in combination with organic manure may be a potential method for not only tobacco production but phytostabilization of Pb-Cd-contaminated soil.

Plant growth and essential oil content and composition of Satureja hortensis L. cv. Saturn in response to calcium carbonate and nitrogen application rates

Satureja hortensis L. (Summer savory) is one of the most important medicinal and spice plants cultivated in many parts of the world. A field experiment was conducted to study the effects of nitrogen (0, 50, 100 and 150 Kg.ha-1) and calcium carbonate (0, 5 and 10 t.ha-1) application rates on the growth and essential oil content and composition of S. hortensis cv. Saturn. Nitrogen (N) fertilization increased plant height, fresh and dry weights of herb, stem diameter, mean of Leaf Area (LA), drug yield and leaf N content as well as essential oil yield. Plant fresh and dry weights and mean of LA were increased by CaCO3 up to 5 t. ha-1. In addition, CaCO3 application positively affected the leaf Ca2+ content and essential oil content and yield, but plant width and leaf N content were negatively affected. The interaction effect of N and CaCO3 application was significant for leaf N and essential oil contents. Gas chromatography-flame ionization detector (GC-FID) and gas chromatography mass spectrometry (GC-MS) analyses of essential oil showed that the chemical compositions of S. hortensis essential oil did not change due to N fertilization while CaCO3application increased the relative percentages of carvacrol, γ-terpinene and β-bisabollene. Key words: Satureja hortensis L., essential oil, calcium carbonate, nitrogen, carvacrol.

EFFECT OF GRAIN BIOINOCULATION ON WHEAT YIELD AND ITS COMPONENTS UNDER APPLYING DIFFERENT LEVELS OF NITROGEN FERTILIZATION

A field experiment was conducted at El-Wanysa village, Itsadistrict, El-Fayoum Governorate, during the two successive winterseasons of 2008/2009 and 2009/2010 to investigate the influence ofapplied different mineral nitrogen levels and grain bio-inoculationwith, Azotobacter and /or Azospirillum and their interactions on wheatgrowth, yield and its attributes as well as N-uptake of either wheatgrain or straw and grain protein content. A split plot design with threereplicates was used. The obtained results could be summarized asfollows:The results showed significant increases in plant dry weight,plant height, spike length, 1000-grain weight, grain or straw yield/fed.N-uptake by straw or grain and of grain protein content either byincreasing the rate of mineral nitrogen or with grain inoculation by thetested N2-fixers. In addition, the dual grain inoculation withAzotobacter and Azospirillum performed significantly greater followedby single inoculation with either Azospirillum or Azotobacter. At anylevel of N-fertilizer, the inoculated treatments gave much higher strawand grain yields than the uninoculated one.From the economical point of view, it could be concluded that,the amount of mineral N-fertilizer could be reduced by using grain bioinoculation, which in turn increases soil fertility as well as, minimizesthe production cost and environmental pollution, which can occur bythe excess use of chemical fertilizers.

Plant Growth-Promoting Fungus, Trichoderma koningi Suppresses Isoflavonoid Phytoalexin Vestitol Production for Colonization on/in the Roots of Lotus japonicus

The relationship between the colonization of Lotus japonicus by plant growth-promoting fungi (PGPF) and biosynthesis of the isoflavonoid phytoalexin vestitol, a major defensive response of leguminous plants, was analyzed. When PGPF including Trichoderma koningi, Fusarium equiseti, and Penicillium simplicissimum were inoculated onto L. japonicus roots, only T. koningi colonized the roots long-term and increased plant dry weight (126%). Microscopic observations of transverse sections of roots colonized by T. koningi demonstrated intercellular hyphal growth and the formation of yeast-like cells. The induction of plant defenses by fungal infections was examined by Northern analysis of genes involved in vestitol biosynthesis and HPLC of vestitol production in L. japonicus. Inoculation with symbiotic Mesorhizobium loti did not induce any accumulation of the transcripts. T. koningi immediately suppressed transcript levels to those induced by M. loti. The vestitol transuded from roots by T. koningi was detected at a level equivalent to that transuded by M. loti. Other PGPF and Calonectoria ilicola pathogenic to soybean but not to L. japonicus, stimulated continuous expression of genes and exudation of vestitol. These PGPF resembled mycorrhizal fungi in the establishment of symbiotic associations rather than fungal parasites.

Utilization of Poultry Manure Phosphorus for Corn Production

There is uncertainty about the need for supplemental P fertilization after applying poultry manure for corn (Zea mays L.). This study evaluated the effects of manure and fertilizer P on corn by establishing 17 on‐farm trials in Iowa. Manure from broilers, egg layers (Gallus gallus domesticus), or turkeys (Melleagris gollopavo) was used at each site. Replicated treatments were the combinations of three manure rates (0, 53, and 104 kg P ha−1 on average across sites) and four triple superphosphate rates (0–75 kg P ha−1). Initial Olsen P (15‐cm depth) was 5 to 23 mg P kg−1 across sites. Uniform rates of 168 kg N ha−1 and 56 to 112 kg K ha−1 were applied. Measurements were early plant dry weight (DW); P concentration and P uptake (V5–V6 stage); and grain yield, P concentration, and P removal. Increases in plant DW and P uptake were unrelated to soil‐test P, were more frequent for manure, and only one site that was responsive (P ≤ 0.10) to fertilizer was not responsive to manure. Phosphorus fertilization in addition to manure increased plant DW at four sites and P uptake at eight sites. Both P sources increased grain yield at eight sites with &lt;15 mg Olsen P kg−1, only manure increased it at another site, and supplemental fertilization did not increase yield at any site. The results provided no evidence for lower P availability of poultry manure P than fertilizer P for corn yield and showed no need for supplemental P fertilization at prevailing manure rates used by farmers.

An Evaluation of Containerized Plants for Strawberries Growing in a Subtropical Environment

The productivity of containerized and bare-rooted plants of strawberry (Fragaria ×ananassa) was investigated over 4 years in southeastern Queensland, Australia. In the first experiment, plants in small, 75-cm3 cells were compared with bare-rooted plants of ‘Festival’ and ‘Sugarbaby’. A similar experiment was conducted in year 2 with these two cultivars, plus ‘Rubygem’. In year 3, plants in large, 125-cm3 cells were compared with small and large bare-rooted plants of ‘Festival’ and ‘Rubygem’. Treatments in each of these experiments were planted on the same date. In the final experiment, plants in large cells and bare-rooted plants of ‘Festival’ were planted in late March, early April, mid-April, or early May. The plants grown in small cells produced 60% to 85% of the yields of the bare-rooted plants, whereas the yield of plants in large cells was equal to that of the bare-rooted plants. Containerized plants are twice as expensive as bare-rooted plants (A$0.60 vs. A$0.32) (A$ = Australian dollar), and gave only similar or lower returns than the bare-rooted plants (A$0.54 to A$3.73 vs. A$1.40 to A$4.09). It can be concluded that containerized strawberry plants are not economically viable in subtropical Queensland under the current price structure and growing system. There was a strong relationship between yield and average plant dry weight (leaves, crowns, and roots) in ‘Festival’ in the last three experiments, where harvesting continued to late September or early October. Productivity increased by about 18 g for each gram increase in plant dry weight, indicating the dependence of fruit production on vegetative growth in this environment.

The effect of application time of mobilising agents on growth and phytoextraction of lead by Brassica napus from a calcareous mine soil

Phytoremediation of heavy metal contaminated sites is often limited by the low-bioavailability of the contaminants. Complexing agents can help to improve this technique by enhancing heavy metal solubility. Pot experiments were conducted to determine the best time for the application of ethylene diamine tetraacetic acid (EDTA) and sheep manure extract (SME) for phytoremediation of a contaminated soil by Brassica napus. The plant was grown on a mine calcareous soil treated with increasing concentrations of EDTA or SME 30 and 10 days before sowing (T1 and T2) and 10 and 30 days after sowing (T3 and T4). Soil available Pb and lead concentrations in plant organs of Brassica napus increased with EDTA concentration. The EDTA application before seed germination significantly reduced rapeseed seedling emergence and dry weight. However, the actual amount of phytoextracted Pb by rapeseed did not decrease significantly, due to severe growth depression, at high EDTA concentrations when it had applied at a suitable time (T4). SME application after sowing increased plant dry weight and Pb concentration in the soil solution and enhanced the accumulated metal concentrations in shoots and roots. Comparing the effect of EDTA and SME on Pb phytoextraction, the study showed that SME is not more effective than EDTA. The efficiency of EDTA on Pb phytoextraction by Brassica napus depends on the time of application. The most efficient treatment for Pb phytoextraction by rapeseed was application of 2 g EDTA/kg soil at T4.

Agronomic and physiological contributions to the yield improvement of soybean cultivars released from 1950 to 2006 in Northeast China

Increasing yield is a high priority in most breeding programs. Approximately 600 soybean cultivars had been released by the end of the last century in Northeast China. Understanding the agronomic and physiological changes is essential for planning further plant breeding strategies in soybean. In this study, 45 representative soybean cultivars, from maturity groups 00 and 0, released from 1950 to 2006 in Northeast China were compared in field conditions for 3 consecutive years. A positive correlation between seed yield and year of cultivar release was indicated with a 0.58% average annual increase. Seed number per plant was the most important contributor to yield gain, with a 0.41% increase per year. Pod number per plant and seed size varied slightly with the year of cultivar release. Although variation in protein was from 37.0% to 45.5%, and oil concentration was from 16.7% to 22.0%, their concentrations were not consistently related to year of cultivar release. A 33% increase in the photosynthetic rate, 10.6% increase in plant dry weight and 19.0% increase in harvest index (HI) were found, while leaf area index (LAI) decreased by 17.3%. Modern cultivars have higher photosynthetic rates than their predecessors. The reduced plant height gave increased resistance to lodging, with the lodging score dropping from 3.2 in 1951 to 1.0 in 2006. Seed resistances to disease and pest infestation were also improved. Yield stability was enhanced over years, which could be attributed to the stable pod production across different environments. A flow diagram to explain the contributors to genetic improvement of soybeans in Northeast China was developed.

Effects of nutrient levels in surface water and sediment on the growth of the floating-leaved macrophyte Trapa maximowiczii: implication for management of macrophytes in East Bay of Lake Taihu, China

Trapa maximowiczii is a floating-leaved macrophyte common in China. The plant population in East Bay, Lake Taihu, has been expanding rapidly in recent years. In order to better understand the mechanisms controlling the population dynamics in this species, two outdoor experiments were conducted from 9 May to 8 July 2007, evaluating the effect on the growth of T. maximowiczii of different nutrient levels in water column and sediment. Results showed that high concentration of nutrients (nitrogen and phosphorous) in water led to significant increases in rosette diameter and plant dry weight, dry weight of aquatic roots and anchoring roots, but had no effect on plant height or main stem node count. Phosphorus enrichment resulted in increases in plant dry weight and seed number. However, no such difference was observed between the nitrogen enrichment treatment and the control. Sediment fertility had significant effects on plant growth. Plant height, plant dry weight, dry weight of aquatic and anchoring roots, and maximum rosette diameter were significantly greater in high-nutrient sediment than those in low-nutrient sediment. This study suggests that eutrophication of water (especially increasing phosphorus loading) and accumulated nutrients in sediment may be among the causes leading to increasing biomass of the floating-leaved macrophyte T. maximowiczii in East Bay of Lake Taihu.

Effect of N fertilizer top-dressing on N accumulation and N2 fixation of supernodulating soybean mutant

Increased application of nitrogen (N) fertilizer top-dressing during growth is an effective option for enhancing N supply to soybean plants. SS2-2 was characterized by the superior ability of symbiotic N2 fixation at the level of 30 kg N ha−1. But, the response of nitrogen fixation ability of supernodulating soybean mutant, SS2-2, to N fertilizer application rate remains unclear. The objective of this experiment was to compare the response of N fertilizer top-dressing on N accumulation and N2 fixation between supernodulating mutant, SS2-2, and wild-type, Sinpaldalkong 2. The effect of N fertilizer top-dressing (0.6 g N pot−1 top-dressing) on the nitrogen accumulation and redistribution were compared between SS2-2 and Sinpaldalkong 2. N fertilizer top-dressing at R1 stage increase in plant dry weight, relative growth rate (RGR), net assimilation rate (NAR), nitrogen harvest index (NHI), and N redistribution (NR). SS2-2 showed highest N concentration, 65.0 mg N g DW−1, followed by Sinpaldalkong 2 and En1282, and the N content per plant did not show a significant difference between SS2-2 and Sinpaldalkong 2. The N2 fixation rate was significantly reduced by N top-dressing, but the amount of N2 fixation was not changed due to an improved dry weight without changes of N concentration. In addition, SS2-2 showed higher NHI, NR and NRE than Sinpaldalkong 2. These results suggested that supernodulating soybean mutants, SS2-2, could be characterized by high N concentration and N2 fixation regardless of N fertilizer top-dressing due to a higher nitrate tolerance of supernodulating mutants than that of wild-type.

Growth response of Acacia mangium Willd. seedlings to arbuscular mycorrhizal fungi and four isolates of the ectomycorrhizal fungus Pisolithus tinctorius (Pers.) Coker and Couch

Some Acacia mangium Willd. plantations in Asia grow poorly due to low soil fertility and the absence of compatible mycorrhizal fungi. This legume tree can be colonized by arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) fungi but inoculation is not routinely practiced. This study aimed to compare the effectiveness of AM fungi and four isolates of the ECM fungus Pisolithus tinctorius (Pers.) Coker and Couch (Pt) in promoting growth of A. mangium seedlings under glasshouse conditions. AM inoculants were: Glomus etunicatum, G. fasciculatum, G. macrocarpum and Gigaspora margarita and mixed species extracted from rhizosphere soil of a Populus stand in Suwon (AMKFRI), and Carex (AMM6) and Populus (AMM7) growing in mine tailings in Korea. Pisolithus isolates were from Philippines (PtPhil) and Korea (PtKFRI, PtMKACC, PtKACC). Generally, ECM fungi promoted height and diameter growth of A. mangium more than the AM inoculants. The Korean Pisolithus increased plant dry weight by 122–145%, mixed AM inoculants by 61–97%, and Glomus and Gigaspora by 45–72% over the control. PtKACC gave the highest root colonization and promoted the highest growth and concentration of most nutrients. Mycorrhizal root colonization was positively correlated with plant dry weight, Na, Fe and Cu concentrations and N, P, K, Ca, Na, Fe and Cu contents. In conclusion, the results provide strong evidence for benefits of mycorrhizal inoculation on A. mangium seedlings under glasshouse conditions. The Korean Pisolithus isolates (particularly PtKACC), and two AM fungi (AMKFRI and AMM6) are potential mycorrhizal inoculants but their effectiveness and persistence should be determined on degraded lands in tropical countries where A. mangium is being planted for rehabilitation.

Combined effect of salicylic acid and salinity on some antioxidant activities, oxidative stress and metabolite accumulation in Phaseolus vulgaris

It has been shown that salicylic acid (SA) acts as an endogenous signal molecule responsible for inducing abiotic stress tolerance in plants. The effect of SA and sodium chloride (NaCl) on growth, metabolite accumulation, oxidative stress and enzymatic and non-enzymatic antioxidant responses on common bean plants (Phaseolus vulgaris, cv. F-15) was studied. Results revealed that either SA or NaCl decrease, shoot, root and total plant dry weights. SA treatments decreased the contents of proline, and reduced forms of ascorbate and glutathione, however, the content of soluble sugars (TSS), thiobarbituric acid-reactive substances (TBARs) and oxidized ascorbate remained unaffected. On the other hand, salinity significantly reduced the levels of endogenous SA but increased the content of proline, soluble sugars, TBARs, ascorbate and glutathione, as well as all increasing the levels of antioxidant enzyme activities assayed, except CAT. The application of SA improved the response of common bean plants to salinity by increasing plant dry weight and decreasing the content of organic solutes (proline and TSS) and damage to the membrane (TBARs). Moreover, SA application under saline conditions decreased the levels of antioxidant enzyme activities POX, APX and MDHAR which could indicate successful acclimatization of these plants to saline conditions.

Liquid Swine Manure Phosphorus Utilization for Corn and Soybean Production

There is uncertainty about manure P availability for crops and need for P fertilization when manure is applied. This study evaluated effects of liquid swine (Sus scrofa domesticus) manure and fertilizer P on early plant growth and P uptake, grain yield, and grain P removal for corn (Zea mays L.) and soybean [Glycine max (L.) Merr.]. Sixteen trials were conducted in Iowa from 2000 to 2002. Replicated treatments were the combinations of three manure rates (0, 29, and 57 kg total P ha−1 on average across sites) and four P fertilizer rates (0 to 30 kg P ha−1). Initial soil Bray‐P1 (15‐cm depth) was 9 to 89 mg P kg−1 Fertilizer rates applied across all plots were 168 kg N ha−1 for corn and 56 to 120 kg K ha−1 for both crops according to soil‐test K. Measurements were early plant dry weight (DW) and P uptake (V5‐V6 stage), grain yield, and grain P removal. Increases in plant DW, P uptake, and grain P removal were unrelated to soil‐test P (STP), and were more frequent to manure than to fertilizer. Yield increases (P ≤ 0.05) were observed at six sites with Bray‐P1 ≤ 20 mg P kg−1, with response only to manure at one site and to both manure and fertilizer at five sites but to fertilizer only when manure was not applied. The study provided no evidence of lower crop‐P availability from liquid swine manure than fertilizer P for corn or soybean in these Iowa fields.

Validamycin A improves the response of Medicago truncatula plants to salt stress by inducing trehalose accumulation in the root nodules

In this work, the role of trehalose as an osmoprotectant against salt stress conditions was examined in root nodules of Medicago truncatula. For this purpose, we used validamycin A, a potent trehalase inhibitor, in order to induce trehalose accumulation. Validamycin A induced an increase of trehalose concentration in root nodules of M. truncatula by inhibiting trehalase activity; no effect on trehalose concentration was observed in roots and leaves. Trehalose accumulation was accompanied by a decrease in sucrose and starch content, indicating interference with carbohydrate partitioning in the plants. Under salinity conditions, sucrose accumulation appears to be induced in M. truncatula to protect nodule functioning by the inhibition of sucrose catabolism by sucrose synthase and alkaline invertase activities. However, trehalose accumulation induced by val A in nodules improved the response to salinity by increasing plant dry weight (PDW), and no effects of validamycin A on nitrogenase activity and PDW were observed in nonsalinized plants.

Phytoextraction of lead by Helianthus annuus: effect of mobilising agent application time

Pot experiments were conducted to determine the best time for application of (ethylenediaminetetraacetic acid) EDTA and sheep manure extract (SME) in phytoremediation of a contaminated soil by &lt;I&gt;Helianthus annuus&lt;/I&gt;. The plant was grown in a mine calcareous soil treated with increasing concentrations of EDTA or SME in 30 and 10 days before sowing (T1 and T2) and 10 and 30 days after sowing (T3 and T4). The best time for EDTA application was T4. The EDTA application before seed germination significantly reduced sunflower seedling emergence and dry weight. Soil available Pb and lead concentrations in plant organs increased with EDTA concentration but the actual amount of phytoextracted Pb decreased at high EDTA concentrations significantly, due to severe growth depression. SME application after sowing can increase plant dry weight and Pb concentration in the soil solution, enhancing the accumulated metal concentrations in shoots and roots. However the results showed that the most efficient treatments for Pb phytoextraction by sunflower are applications of 0.5 and 2 g EDTA/kg soil at T3 and T4, respectively.