Solid-state fermentation of agro-industrial wastes to produce bioorganic fertilizer for the biocontrol of Fusarium wilt of cucumber in continuously cropped soil

Agro-industrial wastes of cattle dung, vinegar-production residue and rice straw were solid-state fermented by inoculation with Trichoderma harzianum SQR-T037 (SQR-T037) for production of bioorganic fertilizers containing SQR-T037 and 6-pentyl-α-pyrone (6PAP) to control Fusarium wilt of cucumber in a continuously cropped soil. Fermentation days, temperature, inoculum and vinegar-production residue demonstrated significant effects on the SQR-T037 biomass and the yield of 6PAP, based on fractional factorial design. Three optimum conditions for producing the maximum SQR-T037 biomass and 6PAP yield were predicted by central composite design and validated. Bioorganic fertilizer containing 8.46 log₁₀ ITS copies g⁻¹ dry weight of SQR-T037 and 1291.73 mg kg⁻¹ dry weight of 6PAP, and having the highest (p < 0.05) biocontrol efficacy, was achieved at 36.7 fermentation days, 25.9 °C temperature, 7.6% inoculum content, 41.0% vinegar-production residue, 20.0% rice straw and 39.0% cattle dung. This is a way to offer a high value-added use for agro-industrial wastes.     

Characterization of transgenic Trifolium subterraneum L. which expresses phyA and releases extracellular phytase: growth and P nutrition in laboratory media and soil

Transgenic Trifolium subterraneum expressing a phytase gene (phyA) from Aspergillus niger were generated. Five independently transformed lines showed an average 77‐fold increase in exuded phytase activity in comparison with null segregant and wild‐type controls. Unlike other phosphatases, exuded phytase activity was unaffected by P supply, verifying the constitutive expression of phyA. Transgenic T. subterraneum grown in agar with P supplied as phytate, took up 1.3‐ to 3.6‐fold more P than controls and had equivalent P uptake to plants supplied with orthophosphate. This unique phenotype was compromised when the plants were grown in soil. None of the five lines showed increased shoot biomass or total P uptake in an unfertilized, low‐P soil taken from under permanent pasture. With addition of P, one of the five transgenic lines had consistently greater P nutrition compared with control plants. Despite variable growth and P nutrition responses, P uptake per root length was on average greater for transgenic lines. Exudation of phytase by transgenic T. subterraneum allowed utilization of P from phytate in non‐sorbing, sterile laboratory media, but was less effective when plants were grown in soil. Release of extracellular phytase is therefore not the only requirement for the acquisition of P from endogenous soil phytate by plants.     

Fermentation of food and feed: A technology for efficient utilization of macro and trace elements in monogastrics

Mineral deficiencies, especially of iron, zinc, and calcium, respectively, negatively affect human health and may lead to conditions such as iron deficiency anemia, rickets, osteoporosis, and diseases of the immune system. Cereal grains and legumes are of global importance in nutrition of monogastrics (humans and the respective domestic animals) and provide high amounts of several minerals, e.g., iron, zinc, and calcium. Nevertheless, their bioavailability is low. Plants contain phytates, the salts of phytic acid, chemically known as inositol-hexakisphosphate, which interact with several minerals and proteins. However, phytate may be hydrolysed by phytase. This enzyme is naturally present in plants and also widely distributed in microorganisms. Several food processing methods have been reported to enhance phytate hydrolysis, due to the activation of endogenous phytase activity or via the enzyme produced by microbes. In recent years, fermentation for food and feed improvement and preservation, respectively, has gained increasing interest as a promising method to degrade phytate and enhance mineral utilization in monogastrics. Indeed, several in vitro as well as in vivo studies confirm a positive effect on the utilization of minerals, such as P, Ca, Fe and Zn, using sourdough fermentation for baking or fermentation of legumes, mainly soybeans. This review summarizes the current knowledge regarding the potential of fermentation to enhance macro and trace element bioavailability in monogastric species.     

Synthesis of Iron-Amino Acid Chelates and Evaluation of Their Efficacy as Iron Source and Growth Stimulator for Tomato in Nutrient Solution Culture

Supplying a sufficient amount of available iron (Fe) for plant growth in hydroponic nutrient solutions is a great challenge. The chelators commonly used to supply Fe in nutrient solutions have several disadvantages and may negatively affect plant growth. In this research study we have synthesized certain Fe-amino acid chelates, including Fe-arginine [Fe(Arg)₂], Fe-glycine [Fe(Gly)₂], and Fe-histidine [Fe(His)₂], and evaluated their efficacy as an Fe source for two tomato cultivars (Lycopersicon esculentum Mill. cvs. ‘Rani’ and ‘Sarika’) grown in nutrient solution. Application of Fe-amino acid chelates significantly increased root and shoot dry matter yield of both tomato cultivars compared with Fe-EDTA. Tomato plants supplied with Fe-amino acid chelates also accumulated significantly higher levels of Fe, Zn, and N in their roots and shoots compared with those supplied with Fe-EDTA. In ‘Sarika’, the effect of Fe-amino acid chelates on shoot Fe content was in the order Fe(His)₂?>?Fe(Gly)₂?>?Fe(Arg)₂. In ‘Rani’, the addition of all synthesized Fe-amino acid chelates significantly increased activity of ascorbate peroxidase (APX) in comparison with Fe-EDTA, whereas in ‘Sarika’, only Fe(His)₂ increased shoot APX activity. The results obtained indicated that using Fe-amino acid chelates in the nutrient solution could supply a sufficient amount of Fe for plant uptake and also improve root and shoot growth of tomato plants, although this increase was cultivar-dependent. According to the results, Fe-amino acid chelates can be used as an alternative for Fe-EDTA to supply Fe in nutrient solutions.     

Bioavailability of zinc sources and their interaction with phytates in broilers and piglets

Zinc (Zn) is essential for swine and poultry and native Zn concentrations in feedstuffs are too low to meet their Zn requirement. Dietary Zn bioavailability is affected by phytate, phytase and Zn supplemented in organic form is considered as more bioavailable than inorganic sources. A meta-analysis using GLM procedures was processed using broiler and piglet databases to investigate, within the physiological response of Zn, (1) the bioavailability of inorganic and organic Zn sources (Analysis I); (2) the bioavailability of native and inorganic Zn dependent from dietary phytates, vegetal and supplemental phytase activity (Analysis II). Analysis I: the bioavailability of organic Zn relative to inorganic Zn sources ranged, depending on the variable, from 85 to 117 never different from 100 (P > 0.05). The coefficients of determination of the regressions were 0.91 in broilers and above 0.89 in piglets. Analysis II: in broilers, bone Zn was explained by supplemental Zn (linear and quadratic, P < 0.001) and by supplemental phytase (linear, P < 0.001). In piglets, the interaction between dietary Zn and phytates/phytases was investigated by means of a new variable combining dietary phytic phosphorus (PP) and phytase activity. This new variable represents the remaining dietary PP after its hydrolysis in the digestive tract, mainly due to phytase and is called non-hydrolyzed phytic phosphorus (PP_NH). Bone Zn was increased with native Zn (P < 0.001), but to a lower extent in high PP or low phytase diets (ZN_N × PP_NH, P < 0.001). In contrast, the increase in bone zinc in response to supplemental Zn (P < 0.001) was not modulated by PP_NH (P > 0.05). The coefficients of determination of the regressions were 0.92 in broilers and above 0.92 in piglets. The results from the two meta-analyses suggest that (1) broilers and piglets use supplemented Zn, independent from Zn source; (2) broiler use native Zn and the use is slightly enhanced with supplemental phytase; (3) however, piglets are limited in the use of native Zn because of the antagonism of non-hydrolyzed dietary phytate. This explains the higher efficacy of phytase in improving Zn availability in this specie.     

Acid phosphomonoesterase and phytase activities of wheat (Triticum aestivum L.) roots and utilization of organic phosphorus substrates by seedlings grown in sterile culture

Wheat seedlings exhibited a differential ability to utilize P from a range of organic P substrates when grown in agar culture under sterile conditions. Plants showed limited ability to obtain P from inositol hexaphosphate (IHP), whereas other monoester substrates such as glucose 1‐phosphate (G1P), were equivalent sources of P for plant growth as compared with inorganic phosphate (P_i). Poor utilization of IHP was exemplified by significantly lower rates of dry matter accumulation and reduced P content of tissues, which were generally not significantly different to control plants that were grown in the absence of added P. The inability of wheat seedlings to obtain P from IHP was not associated with poor substrate availability but was due to either insufficient root phytase activity or inappropriate localization of phytase within root tissues. Phytase activities of 4 and 24 mU g ^{? 1} root fresh weight (FW) were determined for crude root extracts prepared from plants that were grown with either adequate P or under deficient conditions, respectively. Similar levels of phytase activity (approximately 12 mU g ^{? 1} FW) were observed in assays using intact roots, although no secreted activity was detected. By comparison, a secreted acid phosphomonoesterase activity was observed, and activities of between 466 and 1029 mU phosphomonoesterase g ^{? 1} root FW were measured for intact roots. On the basis of the differences in enzyme activity, and the observed differences in the ability of wheat seedlings to utilize G1P and IHP, it is evident that low intrinsic levels of phytase activity in wheat roots is a critical factor that limits the ability of wheat to obtain P from phytate when supplied in agar under non‐limiting conditions. This hypothesis was further supported by the observation that the ability of wheat to obtain P from IHP was significantly improved when the seedlings were inoculated with a soil bacterium (Pseudomonas sp. strain CCAR59) that possesses phytase activity.     

Trichoderma harzianum SQR-T037 rapidly degrades allelochemicals in rhizospheres of continuously cropped cucumbers

To alleviate the stress of continuous cropping for cucumber continuous cropping (CCC) system, a beneficial fungus Trichoderma harzianum SQR-T037 (SQR-T037) was isolated and applied to soil to degrade allelochemicals exuded from cucumber plants in a Rhizobox experiment. The following phenolic acids (PAs), classified as allelochemicals, were isolated and identified from cucumber rhizospheres: 4-hydroxybenzoic acid, vanillic acid, ferulic acid, benzoic acid, 3-phenylpropionic acid, and cinnamic acid. Mixed PAs added in potato dextrose broth, each with 0.2 gram per liter, were completely degraded by SQR-T037 after 170 h of incubation. In Rhizobox experiments, inoculation of SQR-T037 in the CCC soil also degraded the PAs exuded from cucumber plant roots. This degradation was 88.8% for 4-hydroxybenzoic acid, 90% for vanillic acid, 95% for benzoic acid, and 100% for ferulic acid, 3-phenylpropionic acid, and cinnamic acid at 45 days after plantation. Simultaneously, a significant (p ≥ 0.05) decrease in the disease index of Fusarium wilt and an increase in dry weights of cucumber plants were obtained in pot experiments by application of SQR-T037. This was mostly attributed to degradation of PAs exuded from cucumber roots in CCC soil by SQR-T037 and alleviation of the allelopathic stress. Application of beneficial microorganisms, such as SQR-T037 that biodegrades allelochemicals, is a highly efficient way to resolve the problems associated with continuous cropping system.     

Effect of particle size and microbial phytase on phytate degradation in incubated maize and soybean meal

The objective of the study was to evaluate the effect of screen size (1, 2 and 3 mm) and microbial phytase (0 and 1000 FTU/kg as-fed) on phytate degradation in maize (100% maize), soybean meal (100% SBM) and maize–SBM (75% maize and 25% SBM) incubated in water for 0, 2, 4, 8 and 24 h at 38°C. Samples were analysed for pH, dry matter and phytate phosphorus (P). Particle size distribution (PSD) and average particle size (APS) of samples were measured by the Laser Diffraction and Bygholm method. PSD differed between the two methods, whereas APS was similar. Decreasing screen size from 3 to 1 mm reduced APS by 48% in maize, 30% in SBM and 26% in maize–SBM. No interaction between screen size and microbial phytase on phytate degradation was observed, but the interaction between microbial phytase and incubation time was significant (P<0.001). This was because microbial phytase reduced phytate P by 88% in maize, 84% in maize–SBM and 75% in SBM after 2 h of incubation (P<0.05), whereas the reduction of phytate P was limited (<50%) in the feeds, even after 24 h when no microbial phytase was added. The exponential decay model was fitted to the feeds with microbial phytase to analyse the effect of screen size and feed on microbial phytase efficacy on phytate degradation. The interaction between screen size and feed affected the relative phytate degradation rate (R_d) of microbial phytase as well as the time to decrease 50% of the phytate P (t1/2) (P<0.001). Thus, changing from 3 to 1 mm screen size increased R_d by 22 and 10%/h and shortened t1/2 by 0.4 and 0.2 h in maize and maize–SBM, respectively (P<0.05), but not in SBM. Moreover, the screen size effect was more pronounced in maize and maize–SBM compared with SBM as a higher phytate degradation rate constant (K_d) and R_d, and a shorter t1/2 was observed in maize compared with SBM in all screen sizes (P<0.05). However, a higher amount of degraded phytate was achieved in SBM than in maize because of the higher initial phytate P content in SBM. In conclusion, reducing screen size from 3 to 1 mm increased K_d and R_d and decreased t1/2 in maize and maize–SBM with microbial phytase. The positive effect of grinding on improving microbial phytase efficacy, which was expressed as K_d, R_d and t1/2, was greater in maize than in SBM.     

Root iron plaque formation and characteristics under N2 flushing and its effects on translocation of Zn and Cd in paddy rice seedlings (Oryza sativa)

Background and Aims

Anoxic conditions are seldom considered in root iron plaque induction of wetland plants in hydroponic experiments, but such conditions are essential for root iron plaque formation in the field. Although ferrous ion availability and root radial oxygen loss capacity are generally taken into account, neglect of anoxic conditions in root iron plaque formation might lead to an under- or over-estimate of their functional effects, such as blocking toxic metal uptake. This study hypothesized that anoxic conditions would influence root iron plaque formation characteristics and translocation of Zn and Cd by rice seedlings.

Methods

A hydroponic culture was used to grow rice seedlings and a non-disruptive approach for blocking air exchange between the atmosphere and the induction solution matrix was applied for root iron plaque formation, namely flushing the headspace of the induction solution with N₂ during root iron plaque induction. Zn and Cd were spiked into the solution after root iron plaque formation, and translocation of both metals was determined.

Key Results

Blocking air exchange between the atmosphere and the nutrient solution by N₂ flushing increased root plaque Fe content by between 11 and 77 % (average 31 %). The N₂ flushing treatment generated root iron plaques with a smoother surface than the non-N₂ flushing treatment, as observed by scanning electron microscopy, but Fe oxyhydroxides coating the rice seedling roots were amorphous. The root iron plaques sequestrated Zn and Cd and the N₂ flushing enhanced this effect by approx. 17 % for Zn and 71 % for Cd, calculated by both single and combined additions of Zn and Cd.

Conclusions

Blocking of oxygen intrusion into the nutrient solution via N₂ flushing enhanced root iron plaque formation and increased Cd and Zn sequestration in the iron plaques of rice seedlings. This study suggests that hydroponic studies that do not consider redox potential in the induction matrices might lead to an under-estimate of metal sequestration by root iron plaques of wetland plants.     

Barley HvPAPhy_a as transgene provides high and stable phytase activities in mature barley straw and in grains

The phytase purple acid phosphatase (HvPAPhy_a) expressed during barley seed development was evaluated as transgene for overexpression in barley. The phytase was expressed constitutively driven by the cauliflower mosaic virus 35S‐promoter, and the phytase activity was measured in the mature grains, the green leaves and in the dry mature vegetative plant parts left after harvest of the grains. The T₂‐generation of HvPAPhy_a transformed barley showed phytase activity increases up to 19‐fold (29 000 phytase units (FTU) per kg in mature grains). Moreover, also in green leaves and mature dry straw, phytase activities were increased significantly by 110‐fold (52 000 FTU/kg) and 57‐fold (51 000 FTU/kg), respectively. The HvPAPhy_a‐transformed barley plants with high phytase activities possess triple potential utilities for the improvement of phosphate bioavailability. First of all, the utilization of the mature grains as feed to increase the release of bio‐available phosphate and minerals bound to the phytate of the grains; secondly, the utilization of the powdered straw either directly or phytase extracted hereof as a supplement to high phytate feed or food; and finally, the use of the stubble to be ploughed into the soil for mobilizing phytate‐bound phosphate for plant growth.     

Assimilation of Phytate-phosphorus by the Extracellular Phytase Activity of Tobacco (Nicotiana tabacum) is Affected by the Availability of Soluble Phytate

Phytate, the major organic phosphorus in soil, is not readily available to plants as a source of phosphorus (P). It is either complexed with cations or adsorbed to various soil components. The present study was carried out to investigate the extracellular phytase activities of tobacco (Nicotiana tabacum variety GeXin No.1) and its ability to assimilate external phytate-P. Whereas phytase activities in roots, shoots and growth media of P_i-fed 14-day-old seedlings were only 1.3–4.9% of total acid phosphatase (APase) activities, P starvation triggered an increase in phytase secretion up to 914.9 mU mg⁻¹ protein, equivalent to 18.2% of total APase activities. Much of the extracellular phytase activities were found to be root-associated than root-released. The plants were not able to utilize phytate adsorbed to sand, except when insoluble phytate salts were preformed with Mg²⁺ and Ca²⁺ ions for supplementation. Tobacco grew better in sand supplemented with Mg-phytate salts (31.9 mg dry weight plant⁻¹; 0.68% w/w P concentration) than that with Ca-phytate salts (9.5 mg plant⁻¹; 0.42%), presumably due to its higher solubility. We conclude that insolubility of soil phytate is the major constrain for its assimilation. Improving solubility of soil phytate, for example, by enhancement of citrate secretion, may be a feasible approach to improve soil phytate assimilation.     

Effect of sulfur and potassium on zinc absorption by barley

Summary Maximum uptake of Zn in barley (Hordeum vulgare L.) seedlings occurred from nutrient solutions containing SO₄−S at 3.5 ppm and K at 6 ppm. Decreased translocation of Zn from roots to tips was observed when plants were grown with lower levels of S and K. Cysteine substituted for SO₄-ion as a source of S in Zn absorption, and more Zn was absorbed with cysteine than with sulfate. The effect of K on Zn absorption seems to be influenced by S nutrition in plants.     

Solubilisation of some naturally occurring metal-bearing minerals, limescale and lead phosphate by Aspergillus niger

The ability of the soil fungus Aspergillus niger to tolerate and solubilise seven naturally occurring metal-bearing minerals, limescale and lead phosphate was investigated. A. niger was able to solubilise four of the test insoluble compounds when incorporated into solid medium: cuprite (CuO₂), galena (PbS), rhodochrosite (Mn(CO₃)_x) and limescale (CaCO₃). A. niger was able to grow on all concentrations of all the test compounds, whether solubilisation occurred or not, with no reduction in growth rate from the control. In some cases, stimulation of growth occurred, most marked with the phosphate-containing mineral, apatite. Precipitation of insoluble copper and manganese oxalate crystals under colonies growing on agar amended with cuprite and rhodochrosite was observed after 1–2 days growth at 25°C. This process of oxalate formation represents a reduction in bioavailability of toxic cations, and could represent an important means of toxic metal immobilisation of physiological and environmental significance.     

Effectiveness of phytase pre-treatment on growth performance,nutrient digestibility and mineral status of common carp (Cyprinus carpio) juveniles fed Moringa by-product based diet

Several anti-nutritional substances are found in plant derivatives for example phytate, that make the nutrients and minerals unavailable to fish, hence leading to poor growth performance. Presence of the anti-nutrient factor such as phytate is a chelated compound and need enzyme for its breakdown and availability of nutrients to improve fish growth. This research work was performed to check the improvement of overall performance of Cyprinus carpio fingerlings by the help of phytase addition in Moringa oleifera by- products based diet. Combination of Moringa seed meal and Moringa leaf meal was utilized as test ingredient to formulate seven test feeds, containing graded levels of phytase (0, 500, 650, 800, 950, 1100 and 1250 FTU kg⁻¹). In feeding trial of 70 days, fingerlings were given feed two times in a day at the rate of 4% of wet weight of their bodies and faeces were collected. According to current results, it was found that growth performance parameters i.e. weight gain; 25 g, specific growth rate; 1.67 and feed conversion ratio; 1.10 were improved to maximum at 950 FTU kg⁻¹. Digestibility of nutrients (crude protein; 73%, crude fat; 71% and gross energy; 67%) and minerals absorption was also maximum (Ca; 70%, Zn; 66%, K; 74%, Mn; 66% and P; 71%) at 950 FTU kg⁻¹. Lowest growth efficiency, nutrient digestibility and mineral absorption were observed in fingerlings fed at control diet (0 FTU kg⁻¹). Results of the current study, proved that 950 FTU kg⁻¹ is the most optimum level of phytase to formulate economical and ecofriendly feed for improved growth of C. carpio fingerlings as it decreases the discharge of minerals and nutrients in water bodies.     

Some isolates of the nematophagous fungus Pochonia chlamydosporia promote root growth and reduce flowering time of tomato

The fungal parasite of nematode eggs Pochonia chlamydosporia is also a root endophyte known to promote growth of some plants. In this study, we analysed the effect of nine P. chlamydosporia isolates from worldwide origin on tomato growth. Experiments were performed at different scales (Petri dish, growth chamber and greenhouse conditions) and developmental stages (seedlings, plantlets and plants). Seven P. chlamydosporia isolates significantly (P < 0.05) increased the number of secondary roots and six of those increased total weight of tomato seedlings. Six P. chlamydosporia isolates also increased root weight of tomato plantlets. Root colonisation varied between different isolates of this fungus. Again P. chlamydosporia significantly increased root growth of tomato plants under greenhouse conditions and reduced flowering and fruiting times (up to 5 and 12 days, respectively) versus uninoculated tomato plants. P. chlamydosporia increased mature fruit weight in tomato plants. The basis of the mechanisms for growth, flowering and yield promotion in tomato by the fungus are unknown. However, we found that P. chlamydosporia can produce Indole‐3‐acetic acid and solubilise mineral phosphate. These results suggest that plant hormones or nutrient ability could play an important role. Our results put forward the agronomic importance of P. chlamydosporia as biocontrol agent of plant parasitic nematodes with tomato growth promoting capabilities.     

Responses to excess iron in sweet potato: impacts on growth, enzyme activities, mineral concentrations, and anatomy

This study aimed to evaluate the effects of different iron concentrations on growth characteristics, antioxidant enzyme activities, nutrient absorption, and anatomical changes in sweet potato (Ipomoea batatas L.). To accomplish this, seedlings from apical branches of plants that had already been established in the greenhouse were rooted in a hydroponic sponge and then transplanted into a hydroponic system intermittently for 2?weeks and irrigated with nutrient solutions containing iron (ferric-EDTA) at concentrations of 0.45, 0.9, 4.5, and 9.0?mmol?L^?1. Height, leaf area, and total biomass were significantly reduced at iron concentrations of 4.5 and 9.0?mmol?L^?1. The iron concentrations in the established leaves and those that developed after the solution supplementation increased significantly. The amounts of other nutrients were also affected, with manganese showing the most significant decrease. The activities of the antioxidant enzymes, superoxide dismutase, and ascorbate peroxidase increased in plants grown in the 9.0?mmol?L^?1 iron solution. At this concentration, however, the stomatal densities were reduced on the abaxial surfaces of the leaves, although the stomatal diameters increased. The ultrastructures of the radical cells showed mitochondrial impairment at high iron concentrations; however, the chloroplast structures remained unaffected.     

Phosphate Starvation Inducible Metabolism in Lycopersicon esculentum: I. Excretion of Acid Phosphatase by Tomato Plants and Suspension-Cultured Cells

Both tomato (Lycopersicon esculentum cv VF 36) plants and suspension cultured cells show phosphate starvation inducible (psi) excretion of acid phosphatase (Apase). Apase excretion in vitro was proportional to the level of exogenous orthophosphate (Pi). Intracellular Apase activity remained the same in both Pi-starved and sufficient cells, while Apase excreted by the starved cells increased by as much as six times over unstressed control cells on a dry weight basis. At peak induction, 50% of total Apase was excreted. Ten day old tomato seedlings grown without Pi showed slight growth reduction versus unstressed control plants. The Pi-depleted roots showed psi enhancement of Apase activity. Severely starved seedlings (17 days) reached only one-third of the biomass of unstressed control plants but, because of a combination of psi Apase excretion by roots and a shift in biomass to this organ, they excreted 5.5 times the Apase activity of the unstressed control. Observed psi Apase excretion may be part of a phosphate starvation rescue system in plants. The utility of the visible indicator dye 5-bromo-4-chloro-3-indolyl-phosphate-p-toluidine as a phenotypic marker for plant Apase excretion is demonstrated.     

The Effect of Titanium Amendment in N-Withholding Nutrient Solution on Physiological and Photosynthesis Attributes and Micronutrient Uptake of Tomato

Titanium (Ti) is a beneficial element that promotes growth and biomass production although the mechanism by which this improvement takes place is still unclear, as are other effects on plants, although it is believed that Ti can compensate for N deficiency. To prove this hypothesis, a hydroponic experiment was designed to investigate the effect of adding Ti to a nutrient solution on the nutrient uptake of tomato (Lycopersicon esculentum L.) by withholding N within the nutrient solution (NS) by 25?% (NS2) and by 50?% (NS1). Ti was added at 1 and 2?mg?L^?1. When Ti was added to nutrient solution, the elemental concentration in tomato changed significantly: K, Ca, Fe, and Zn decreased while Ti increased. As the concentration of N in nutrient solution decreased, the Ca and Ti concentration of tomato leaves decreased and the K, Mn, Fe, Cu, and Zn concentration increased. As the N concentration in nutrient solution increased, the Ca concentration decreased although the application of Ti compensated for Ca concentration in NS1. All the photosynthetic attributes and physiological characteristics, including flower induction, decreased when the N concentration of NS decreased by 50?%, although this decrease could be compensated by applying 1?mg?L^?1 Ti. This has valuable and practical applications and implications for tomato hydroponic culture.     

Zinc, Iron, and Chlorophyll Metabolism in Zinc-toxic Corn

Zinc toxicity and Zn-Fe interactions were studied in corn (Zea mays L. var. Barbecue hybrid) grown in hydroponic culture. High Zn greatly reduced the root and shoot fresh weights; increasing Fe largely, but not completely, restored normal growth. Correlation analyses of root and leaf Zn and Fe contents suggested that Zn may interfere with the translocation of Fe; however, Zn toxicity was not associated with a diminished leaf Fe content. Fe did appear to retard both the absorption and the translocation of Zn. The chlorosis of Zn-toxic plants is not attributable to diminshed total leaf Fe; however, this chlorosis is relieved by increasing nutrient Fe. Zn and Fe probably do interact at some site.