Silicon Requirement of Coarse and Fine Varieties of Rice

ABSTRACT

Silicon (Si) provides extra strength to plants against lodging. A hydroponic study was conducted to compare Si requirements of three high yielding, nitrogen (N) responsive, coarse varieties of rice (KSK-133, PK-3717-12, and IRRI-6) with four low yielding, lodging susceptible, fine varieties of rice (BAS-191, BAS-385, BAS-370, and PK-3300). Two-week-old uniform seedlings were grown in half strength Johnson's nutrient solution containing 0, 25, 75, and 150 mg Si kg^{? 1} as sodium silicate. The plants were allowed to grow for 45 days after transplanting. Silicon application significantly (P ≤ 0.01) increased root and shoot dry matter production in all the rice varieties. The maximum shoot dry matter production occurred at 75 mg Si kg^?1 and decreased uniformly in all the rice varieties at 150 mg Si kg^{? 1}. However, growth response to Si application varied significantly (P ≤ 0.01) among various rice varieties. Root: shoot growth ratio, varying from 0.11 to 0.15, did not follow any trend. Different rice varieties and Si addition had a significant (P ≤ 0.01) main and interactive effect on concentration and total uptake of Si in rice root and shoot. Relative increases in Si content, both in shoot and root, were gradual and several fold with increasing rates of Si application. The effect was more pronounced in Basmati varieties (BAS-198, BAS-385, and BAS-370) than other varieties. A 0.91 mg Si g^{? 1} plant tissue was optimum for growth of KSK-133 (coarse), which was significantly higher than the optimum level, 0.62 mg Si g^{? 1} plant tissue, for Bas-370 (fine). However, further verification of the results is warranted under field situation.     

Phytosiderophore release by Sorghum,wheat, and corn under zinc deficiency 1

Zinc (Zn) deficiency is more common in corn (Zea mays L.) than in sorghum [Sorghum bicolor (L.) Moench] or wheat (Triticum sp.). The ability of wheat to withstand low soil Zn conditions is related to increased release of phytosiderophore from its roots. The reasons for sorghum's ability and corn's inability to utilize low levels of soil Zn have not been explored adequately. The objectives of this research were to 1) ascertain if Zn deficiency could be induced in sorghum, wheat, and corn grown in a chelator‐buffered nutrient solution and 2) determine relative releases of phytosiderophore from roots of sorghum, wheat, and/or corn under Zn‐deficiency conditions. Sorghum, wheat, and corn were grown hydroponically in the greenhouse with a chelator‐buffered nutrient solution designed to induce Zn deficiency, while supplying adequate amounts of other nutrients. Root exudates were collected over time to measure phytosiderophore release. Shoot Zn concentrations and shoot and root dry matter yields were determined also. The technique was effective for inducing Zn deficiency in sorghum, wheat, and corn, as evidenced by reduced shoot and root dry matter yields, shortened internodes, reduced shoot Zn concentrations, and plant Zn concentrations below the suggested critical values for these species. Sorghum and wheat plants increased the release of phytosiderophore in response to Zn deficiency, but com did not. The total amount of phytosiderophore released by the roots was in the order wheat>sorghum>corn. The absence of a “phytosiderophore”; response to Zn deficiency of corn, coupled with the evidence that this species requires, or at least accumulates, more Zn than wheat or sorghum, provides an explanation as to why Zn deficiencies are more prevalent for corn than wheat or sorghum under field conditions.     

Is the salt tolerance of maize related to sodium exclusion? I. Preliminary screening of seven cultivars

Maize (Zea mays L.) plants in the early stage of development were treated with 80 mM sodium chloride (NaCl) with or without supplemental calcium (Ca²⁺) (8.75 mM) for a seven day period. The effects of salinity on dry matter production and shoot and root concentrations of sodium (Na⁺), Ca²⁺, and potassium (K⁺) were measured for seven Pioneer maize cultivars. Salinity significantly reduced total dry weight, leaf area, and shoot and root dry weight below control levels. For all seven cultivars, Na⁺concentrations were reduced and leaf area was significantly increased by supplementing salinized nutrient solutions with 8.75 mM calcium chloride (CaCl₂). The two cultivars with the lowest shoot and root Na⁺ concentrations under NaCl‐salinity showed the greatest increases in total, shoot and root dry weights with the addition of supplemental Ca. Shoot fresh weight/dry weight ratios for all cultivars were decreased significantly by both salinity treatments, but supplemental Ca²⁺ increased the ratio relative to salinity treatments without supplemental Ca. Root fresh weight/dry weight ratios were decreased only by salinity treatments with supplemental Ca. With NaCl‐salinity, cultivars which had lower shoot and root Na⁺ concentrations were found to be more salt sensitive and had significantly lower amounts of dry matter production than those cultivars which had higher shoot and root Na⁺ concentrations. It was concluded that Na⁺ exclusion from the shoot was not correlated with and was an unreliable indicator of salt tolerance for maize.     

Effects of excess manganese on mineral uptake in mycorrhizal sorghum

Associations between vesicular‐arbuscular mycorrhizal (VAM) fungi and manganese (Mn) nutrition/toxicity are not clear. This study was conducted to determine the effects of excess levels of Mn on mineral nutrient uptake in shoots and roots of mycorrhizal (+VAM) and non‐mycorrhizal (‐VAM) sorghum [Sorghum bicolor (L) Moench, cv. NB9040]. Plants colonized with and without two VAM isolates [Glomus intraradices UT143–2 (UT1 43) and Gl. etunicatum UT316A‐2 (UT316)] were grown in sand irrigated with nutrient solution at pH 4.8 containing 0, 270, 540, and 1080 μM of added Mn (as manganese chloride) above the basal solution (18 μM). Shoot and root dry matter followed the sequence of UT316 > UT143 > ‐VAM, and shoots had greater differences than roots. Shoot and root concentrations and contents of Mn, phosphorus (P), sulfur (S), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), zinc (Zn), and copper (Cu were determined. The +VAM plants generally had higher mineral nutrient concentrations and contents than ‐VAM plants, although ‐VAM plants had higher concentrations and contents of some minerals than +VAM plants at some Mn levels. Plants colonized with UT143 had higher concentrations of shoot P, Ca, Zn, and Cu and higher root Mg, Zn, and Cu than UT316 colonized plants, while UT316 colonized plants had higher shoot and root K concentrations than UT143 colonized plants. These results showed that VAM isolates differ in enhancement of mineral nutrient uptake by sorghum.     

Silicon mitigates boron deficiency and toxicity in cotton cultivated in nutrient solution

Silicon (Si) application, both via foliar application and via roots, may be promising to improve plant growth under different biotic or abiotic stresses. In the present study, we investigated whether application of Si can also mitigate the harmful effects of boron (B)‐related nutritional disorders, such as B deficiency, when the application of B is inefficient or insufficient, and B toxicity, when the soil presents high levels of B. This may enable producers to apply Si preventively, if there is a low availability of B in the environment or if B deficiency is induced during the growth season due to a water deficit reducing the plant's B absorption. The objective of this study was to investigate the influence of leaf and root Si application on alleviating the harmful effects of B deficiency and toxicity in cotton. Three experiments were carried out with cotton plants (Gossypium hirsutum cv. Bayer FM910®), using a soilless system. In a first experiment, we determined that highest plant Si concentrations were obtained with application of stabilized sodium and potassium silicate at concentrations of 0.8 g L^?1 (foliar) and 0.056 g L^?1 (roots). Experiment 2 indicated that the B concentrations in the nutrient solution associated with moderate B deficiency, sufficiency and moderate toxicity were 33.7, 83.6, and 130.5 µM B L^?1, respectively. In Experiment 3 we evaluated the effect of optimum Si applications on the physiology and dry weight production of cotton plants subjected to B deficiency, sufficiency, and toxicity. Silicon mitigated the harmful effects of both B deficiency and toxicity by increasing whole‐plant biomass production and levels of chlorophyll a, chlorophyll b, and total chlorophyll, and reduced initial and maximum fluorescence, thereby improving the quantum efficiency of photosystem II. Collectively, these results indicate that the greatest benefit of Si in mitigating B deficiency occurred with foliar B application, while Si supplied via the nutrient solution was more effective against B toxicity.     

Nutrient deficiency symptoms and boron uptake mechanisms of rice

There is little agreement on the leaf and shoot boron (B) requirement of rice (Oryza saliva L.) and the optimum hydroponic solution B concentration for rice. Questions on the mechanism of B uptake active or passive are also unresolved. We grew rice in hydroponic solutions in a growth chamber for six weeks with B at 0, 0.05, 0.2, 1, 5, 10, 25, and 50 μM. Transpirational flow, dry matter yields and tissue B were determined. Results indicated that B deficiency occurred when there was <7.3 mg kg^‐1 B in the flag leaves, <3.6 mg kg^‐1 B in shoots, and <0.2 μM B in the nutrient solutions. Boron additions increased dry matter and plant height. Typical B‐deficiency symptoms were a light color or chlorosis on almost all of the youngest leaves and stems, an unthriftiness, leaf tip burn, and pale bands 2–3 mm wide on leaves, particularly on the moderately B‐deficient plants. Whitish and twisted new leaf tips occurred at >0.05 μM B. A mass balance analysis that compared the total mass of B in the plant versus B provided via transpirational flow showed that at high hydroponic B supply, passive uptake and active excretion of B, or, active blockage of B may have occurred, for > 10‐fold differences existed between the B mass in plant and B mass that could be provided via transpirational flow. Thus, B uptake was against a concentration gradient and high B supply, and as other evidence indicated, at low B supply.     

Silicon: a beneficial nutrient for maize crop to enhance photochemical efficiency of photosystem II under salt stress

Soil salinity imposes an unprecedented risk to the soil fertility and availability of plant nutrients. The present proposal is designed to address the effect of salt stress on photosynthetic apparatus of maize including chlorophyll a fluorescence and how silicon nutrition helps to overcome this issue. In a sand culture experiment, two maize cultivars were sown in small pots with two levels of silicon (0 and 2 mM H₂SiO₃) and two levels of salinity stress (0 and 60 mM NaCl). Salinity stress reduced dry matter yield and potassium (K) concentration in both maize cultivars and also induced inefficient working of photosynthetic apparatus including photochemical efficiency of photosystem II. Silicon addition alleviated NaCl stress on maize crop by improving the dry matter yield and water use efficiency (WUE). It decreased shoot Na concentration by increasing root and shoot K concentration of maize plants. It enhanced maximum quantum yield of primary photochemistry which leads to smooth electron transport chain. It also significantly enhanced shoot silicon concentration and has a significant positive correlation with WUE. Therefore, silicon-treated maize plants have better chance to survive under salt stress conditions as their photosynthetic apparatus is working far better than non-silicon-treated plants.     

Adequate range of boron nutrition is more restricted for root nodule development than for plant growth in young soybean plant

A pot experiment was conducted under growth chamber conditions to determine the lower and upper critical levels of boron (B) for plant growth, nodule development, and nodule acetylene reduction activity (ARA) in young soybean plants. Plants of a soybean cultivar, Tachinagaha, were grown in pots containing river sand to which a nutrient solution with different B levels was added and were inoculated with Bradyrhizobium japonicum A1017. At 8, 12, and 16 d after sowing (DAS), among the plants supplied with the solution at 0, 1.0, and 2.0 mg B L^-1 , plants with 1.0 mg B L^-1 showed the highest values for dry shoot and fresh root weight, root length, total number of developing nodules and meristematic nodules (DMN), and ARA. At 20 DAS plants grown with 11 B levels (0-2.0 mg L^-1) were compared. The B critical deficiency levels for soybean dry shoot weight, fresh root weight, root length, DMN, number of complete nodules, and ARA were approximately 46, 35, 34, 57, 60, and 50 mg B kg^-1 dry matter, and the critical toxicity levels were approximately 114, 137, 134, 97, 104, and 89 mg B kg^-1 dry matter, respectively. The optimum B levels for the growth characters were approximately 34 to 137 mg B kg^-1 dry matter. The optimum range of B levels for nodule formation and function was more restricted than that for the growth characters. Based on the results of treatments with various B concentrations, 0.4 mg B L^-1 was found to be the concentration most beneficial for all the growth characters including nodule formation at the early stage (20 DAS) of development of soybean plants.     

Boron toxicity in kiwifruit plants (Actinidia deliciosa), treated with nitrate,ammonium, and a mixture of both

The objective of this research was to study the effects of nitrogen (N) forms (NO₃^–, 2.6 mM; NH₄⁺, 2.6 mM; NO₃^–, 1 mM + NH₄⁺, 1.6 mM) on the growth and mineral composition of kiwifruit plants exposed to three boron (B) levels (0.025, 0.1, 0.3 mM). The kiwifruit plants were grown in a 1:1 sand : perlite mixture and irrigated daily with nutrient solutions. Shoot height, mean shoot dry weight, the number of leaves, mean leaf dry weight, and N concentration of NH₄‐treated plants were significantly higher compared to the NO₃^– treatment at all B levels. The concentration of 0.3 mM B significantly reduced shoot height for all N treatments. Boron toxicity symptoms appeared 14 days after starting the experiment, when plants were treated with 0.1 and/or 0.3 mM B. The nitrate supply reduced the B concentration of roots, but B levels of different leaf parts were hardly affected by the N form. Furthermore, the NH₄‐N form significantly reduced the Mg concentration of the leaves.     

硅、磷配施对玉米苗期生长及氮磷钾积累的影响

以‘正红2号’和‘正红115’玉米为材料,采用砂培方式,设置3个纯磷水平[1.0 mmol·L~(-1)(正常磷水平,P_(1.0))、0.1 mmol·L~(-1)(中度缺磷,P_(0.1))和0.01 mmol·L~(-1)(重度缺磷,P_(0.01))]和3个纯硅水平[1.5 mmol·L~(-1)(Si_(1.5))、0.75mmol·L~(-1)(Si_(0.75))和0 mmol·L~(-1)(Si_0)],通过对玉米苗期干物质、叶面积、根系形态和氮磷钾含量的测定分析,研究硅、磷配施对玉米苗期根系生长、各器官干物质及氮、磷和钾养分积累与利用的影响,为磷、硅肥合理配施提供理论依据。结果表明:缺磷抑制玉米苗期生长,降低根长、根体积、根表面积和叶面积,减少磷和氮、钾的吸收以及干物质积累量,这种效应随磷浓度的降低而增强;玉米通过提高根冠比,增加磷、氮在根系中的分配率,提高氮、磷、钾的干物质生产效率来适应低磷环境;低磷胁迫对‘正红115’根系生长和磷吸收积累量的影响大于‘正红2号’,但‘正红115’在低磷条件下大幅度提高磷在根系中的分配率。在正常磷(P_(1.0))条件下加硅可促进玉米根系生长,增加磷和氮、钾积累量,提高其在地上部分配率,增加叶面积和干物质积累量;在中度缺磷(P_(0.1))条件下加硅也可增加玉米的磷和氮、钾积累量,促进根系和地上部生长,缓解低磷胁迫;在重度缺磷(P_(0.01))条件下,增施硅对玉米根系生长和干物质积累无显著的改善作用,但会增加根系中磷、钾素积累量。由此表明,硅和磷存在显著的协同作用和配合效应,生产上硅和磷应配施。     

Root morphology of maize under homogeneous or spatially separated supply of ammonium and nitrate at three concentration ratios

Maize (Zea mays L. cv. Anjou 256) seedlings were grown hydroponically for 10 d in a split‐root system (3mM N; pH 5.5) under either a homogeneous supply (HS) or a simultaneous, but spatially separated supply (SS) of NH₄ ⁺ andNO₃ ^‐. Treatments comprised three NH₄ ⁺:NO₃ ^‐ ratios (1:4, 1:1, 4:1). Shoot dry matter and various root traits (dry matter, number of laterals, length of main axes, total root length and total root surface area) were determined. For all NH₄ ⁺:NO₃ ^‐ ratios, shoot dry matter, root dry matter, total root length, and root surface area, were greater under HS than under SS. Under both SS and HS, increasing NH₄ ⁺:NO₃ ^‐ ratios resulted in decreased shoot and root dry matter production, but did not alter the shoot:root dry matter ratio. Under SS, root dry matter, root length, and root surface area was greater on the NO₃ ^‐‐fertilized side than on the NH₄ ⁺ ‐fertilized side. The allocation of root dry matter, root length, and root surface area to the NH₄ ⁺ or NO₃ ^‐ compartments was unaffected by changes in the NH₄ ⁺:NO₃ ^‐ ratio. Enhanced NH₄ ⁺ nutrition has detrimental effects on top growth, but roots are apparently unable to avoid excessive NH₄ ⁺ uptake by proliferating in zones where NO₃ ^‐ is the only form of N.     

Silicon-induced changes in growth,ionic composition,water relations,chlorophyll contents and membrane permeability in two salt-stressed wheat genotypes

We investigated the effect of exogenously applied silicon (Si) on the growth and physiological attributes of wheat grown under sodium chloride salinity stress in two independent experiments. In the first experiment, two wheat genotypes SARC-3 (salt tolerant) and Auqab 2000 (salt sensitive) were grown in nutrient solution containing 0 and 100 mM sodium chloride supplemented with 2 mM Si or not. Salinity stress substantially reduced shoot and root dry matter in both genotypes; nonetheless, reduction in shoot dry weight was (2.6-fold) lower in SARC-3 than in Auqab 2000 (5-fold). Application of Si increased shoot and root dry weight and plant water contents in both normal and saline conditions. Shoot Na⁺ and Na⁺:K⁺ ratio also decreased with Si application under stress conditions. In the second experiment, both genotypes were grown in normal nutrient solution with and without 2 mM Si. After 12 days, seedlings were transferred to 1-l plastic pots and 150 mM sodium chloride salinity stress was imposed for 10 days to all pots. Shoot growth, chlorophyll content and membrane permeability were improved by Si application. Improved growth of salt-stressed wheat by Si application was mainly attributed to improved plant water contents in shoots, chlorophyll content, decreased Na⁺ and increased K⁺ concentrations in shoots as well as maintained membrane permeability.     

Metabolite profiling of shoot extract,root extract,and root exudate of rice under nitrogen and phosphorus deficiency

ABSTRACT

Root exudate is derived from plant metabolites and its composition is affected by plant nutrient status. A deficiency of mineral nutrients, such as nitrogen (N) and phosphorus (P), strongly affects the type and amount of plant metabolites. We applied a metabolite profiling technique to investigate root exudates of rice plants under N and P deficiency. Oryza sativa was grown in culture solution containing two N levels (0 and 60 mg N L^?1) or two P levels (0 and 8 mg P L^?1). Shoot extracts, root extracts, and root exudates were obtained from the rice plants 5 and 15 days after transplanting and their metabolites were determined by capillary electrophoresis/time-of-flight mass spectrometry. Shoot N concentration and dry weight of rice plants grown at ?N level were lower than those of plants grown at +N level. Shoot P concentration and dry weight of rice plants grown at ?P level were lower than those of plants grown at +P level. One hundred and thirty-two, 127, and 98 metabolites were identified in shoot extracts, root extracts, and root exudates, respectively, at the two N levels. One hundred and thirty-two, 128, and 99 metabolites were identified in shoot extracts, root extracts, and root exudates, respectively, at the two P levels. Seventy-seven percent of the metabolites were exuded to the rhizosphere. The concentrations of betaine, gamma-aminobutyric acid, and glutarate in root exudates were higher at both ?N and ?P levels than at their respective high levels. The concentration of spermidine in root exudates was lower at both ?N and ?P levels than at their respective high levels. The concentrations of the other metabolites in root exudates were affected differently by plant N or P status. These results suggest that rice roots actively release many metabolites in response to N and P deficiency.     

Maize growth and mineral acquisition on acid soil amended with flue gas desulfurization by‐products and magnesium

Abstract

The large amounts of coal combustion by‐products (CCBs) generated by coal burning power plants must be utilized or discarded, and beneficial use of these materials are desired. One beneficial use of CCBs could be application to agricultural land. Information about the use of one kind of CCB (flue gas desulfurization by‐product, FGD‐BP) on soil is limited. Maize (Zea mays L.) was grown (greenhouse) on an acid soil [Umbric Dystrochrept, pH_Ca (1:1, soil: 10 mM CaCl₂) 4.2] amended with two high CaSO₄ FGD‐BPs (5 and 15 g#lbkg^‐1 soil) and CaCQ₃ (2.5 and 5.0 g#lbkg^‐1 soil) at varied calcium/magnesium (Ca/Mg) equivalency ratios (0/0, 1/0, 1/0.01, 1/0.05, 1/0.1, and 1/0.5) to determine treatment effects on growth traits [shoot and root dry matter (DM) and total and specific root length (RL)], mineral concentrations in leaves, and soil pH and electrical conductivity [(EC) 1:1, soil:water]. Magnesium deficiency symptoms were induced on leaves of plants grown with and without low Mg, and the Mg to Ca ratio in each amendment needed to be about 1 to 20 to alleviate Mg deficiency. Shoot and root DM and total RL of plants grown with FGD‐BPs became higher as Mg increased. Specific RL (total RL/root DM, root fineness) was not affected by FGD‐BP and only slightly by Ca/Mg ratio. Shoot concentrations of Mg increased; Ca, phosphorus (P), and manganese (Mn) decreased; and potassium (K), sulfur (S), iron (Fe), zinc (Zn), and copper (Cu) remained relatively constant as amendment and Mg increased. On unamended soil, aluminum (A1) and Mn concentrations in shoots were above normal. Enhancement of growth was closely related to increased soil pH compared to added Mg for CaCO₃ amended soil and to increased Mg compared to increased soil pH for FGD‐BP amended soil. Except at the highest level of Mg where soil pH increased, added FGD‐BPs and Mg had only limited effect on increasing soil pH. Soil EC increased from added FGD‐BPs but not from added Mg, and EC was not sufficiently high to be detrimental to plants. Maize grown on this acid soil amended with FGD‐BPs received benefits when caution was used to alleviate mineral deficiencies/toxicities inherent in the soil.     

Silicon alleviates mercury toxicity in garlic plants

Abstract

Silicon (Si) can increase plant stress tolerance. Mercury (Hg) is one of the major elements of heavy metal pollution. However, little attention has been paid to the possible effect of Si on Hg toxicity in plants. Here, the effects of Si on growth, photosynthesis, Hg accumulation and antioxidant defense were investigated in garlic grown in pots under Hg stress. Before sowing, Hg and Si were added at 3?mg Kg^?1 and 500?mg Kg^?1, respectively. The treatments included CT (control), Si, Hg and Hg?+?Si. The results showed that in non-stress conditions, added Si did not affect the garlic growth, photosynthetic gas exchange, malonaldehyde concentration or activities of antioxidant enzymes in leaves, except that it increased the superoxide dismutase activity. Under Hg stress, the garlic growth, leaf net photosynthetic rate, stomatal conductance, transpirational rate and superoxide dismutase activity in leaves were all inhibited, while the malondialdehyde concentration was increased; whereas these changes were all reversed in the presence of added Si. Added Si significantly decreased Hg concentrations in the root, bulb and shoot, and it also decreased exchangeable Hg level in the soil. These results suggest that Si could alleviate Hg toxicity in garlic through improving antioxidant defense ability, and decreasing Hg availability in soil and thus Hg uptake.     

Upland rice genotypes evaluation for phosphorus use efficiency

Phosphorus (P) deficiency is one of the most important yield‐limiting factors in acid soils in various parts of the world. The objective of this study was to evaluate the growth and P‐use efficiency of 20 upland rice (Oryza sativa L.) genotypes at low (0 mg P kg^‐1), medium (75 mg P kg^‐1), and high (150 mg P kg^‐1) levels of applied P on an Oxisol. Plant height, tillers, shoot and root dry weight, shoot‐root ratio, P concentration in root and shoot, P uptake in root and shoot, and P‐use efficiency were significantly (P<0.01) affected by level of soil P as well as genotype. Shoot weight and P uptake in shoot were found to be the plant parameters most sensitive to P deficiency, suggesting that these two parameters may be most suitable for screening rice genotypes for P‐use efficiency under greenhouse conditions.     

Relationships between shoot and root characteristics of white clover cultivars differing in response to phosphorus

Root dry weight and the relationship between shoot and root characteristics for 119 white clover (Trifolium repens L.) cultivars and breeding lines were examined at five (40, 120, 200, 400, and 500 mg P/kg soil) phosphorus (P) levels. There were significant (P<0.01) differences among cultivars for root dry weight and root/shoot ratio. Instantaneous root/shoot ratio decreased with increasing P supply up to 200 mg P/kg, and then increased again from 400 to 500 mg P/kg soil. Allometric analysis indicated that root growth relative to shoot growth increased with increasing P supply. There was a significant (P<0.01) cultivar x P level interaction such that for the cultivars, the root/shoot ratio was either unaffected, increasing, or decreasing with increasing level of P supply. However, root/shoot ratio appeared to be unrelated to the functions used to describe the P response of the 119 cultivars studied. Shoot characters such as dry weight, leaf number, and stolon length were most closely correlated with root dry weight at the moderately low P levels of 120 and 200 mg added P/kg, where average P response was 9 and 24% of yields at 500 mg P/kg soil, respectively, rather than at the higher P levels. Root/shoot ratio was significantly correlated (r>0.6) with root dry weight over all P levels but not with any of the measured shoot characters (‐0.2> r <0.3).     

Influence of Gyttja on Shoot Growth and Shoot Concentrations of Zinc and Boron of Wheat Cultivars Grown on Zinc‐Deficient and Boron‐Toxic Soil

Abstract

Greenhouse experiments were carried out to study the influence of gyttja, a sedimentary peat, on the shoot dry weight and shoot concentrations of zinc (Zn) and boron (B) in one bread wheat (Triticum aestivum L., cv. Bezostaja) and one durum wheat (Triticum durum L., cv. Kiziltan) cultivar. Plants were grown in a Zn‐deficient (DTPA‐Zn: 0.09 mg kg^?1 soil) and B‐toxic soil (CaCl₂/mannitol‐extractable B: 10.5 mg kg^?1 soil) with (+Zn = 5 mg Zn kg^?1 soil) and without (?Zn = 0) Zn supply for 55 days. Gyttja containing 545 g kg^?1 organic matter was applied to the soil at the rates of 0, 1, 2.5, 5, and 10% (w/w). When Zn and gyttja were not added, plants showed leaf symptoms of Zn deficiency and B toxicity, and had a reduced growth. With increased rates of gyttja application, shoot growth of both cultivars was significantly enhanced under Zn deficiency, but not at sufficient supply of Zn. The adverse effects of Zn deficiency and B toxicity on shoot dry matter production became very minimal at the highest rate of gyttja application. Increases in gyttja application significantly enhanced shoot concentrations of Zn in plants grown without addition of inorganic Zn. In Zn‐sufficient plants, the gyttja application up to 5% (w/w) did not affect Zn concentration in shoots, but at the highest rate of gyttja application there was a clear decrease in shoot Zn concentration. Irrespective of Zn supply, the gyttja application strongly decreased shoot concentration of B in plants, particularly in durum wheat. For example, in Zn‐deficient Kiziltan shoot concentration of B was reduced from 385 mg kg^?1 to 214 mg kg^?1 with an increased gyttja application. The results obtained indicate that gyttja is a useful organic material improving Zn nutrition of plants in Zn‐deficient soils and alleviating adverse effects of B toxicity on plant growth. The beneficial effects of gyttja on plant growth in the Zn‐deficient and B‐toxic soil were discussed in terms of increases in plant available concentration of Zn in soil and reduction of B uptake due to formation of tightly bound complexes of B with gyttja.     

Bicarbonate Had Greater Effects Than High pH on Inhibiting Root Growth of Zinc‐Inefficient Rice Genotype

Abstract

Effects of bicarbonate (10 mM as NaHCO₃) and high pH (pH 8 buffered with HEPES) separately on root growth and accumulation of organic acids in the roots of zinc (Zn)‐efficient (IR36) and Zn‐inefficient (IR26) rice genotypes (Oriza sativa L.) were investigated in this study. The results indicated that shoot dry matter yields were decreased more by bicarbonate than by high pH for the Zn‐inefficient genotype, but not affected for the Zn‐efficient genotype. Root dry weights, especially root length, was significantly decreased by bicarbonate and high pH treatments for the Zn‐inefficient genotype, whereas was considerably enhanced by only bicarbonate treatment for the Zn‐efficient rice genotype. The reduction in root growth of the Zn‐inefficient rice genotype and the enhancement of root length in the Zn‐efficient genotype were greater when plants grown with bicarbonate than with high pH treatment. Accumulation of malate, citrate, and fumarate in roots of the two genotypes increased considerably due to both high pH and bicarbonate treatments, but to a greater extent for the Zn‐inefficient than for the Zn‐efficient cultivars. After an 8‐day treatment, more organic acids accumulated in the roots of the Zn‐inefficient genotype (IR26) when plants grown with bicarbonate than at high pH, but this was not the case for the Zn‐efficient genotype. The influence of root growth by bicarbonate appeared to be one of the major factors for the sensitivity of rice genotypes to Zn deficiency in calcareous soils. The greater inhibitory effect of bicarbonate than high pH on root growth of the Zn‐inefficient genotype might result from an excessive accumulation and inefficient compartmentation of organic acids, particularly citrate and malate, in the root cells.     

Potassium and sodium fertilization affects leaf nutrient content and growth of ‘Shawnee’ blackberry

Aluminum (Al) has many detrimental effects on plant growth, and shoots and roots are normally affected differently. A study was conducted to determine differences among sorghum [Sorghum bicolor (L.) Moench] genotypes with broad genetic backgrounds for growth traits of plants grown at 0,200,400,600, and 800 μM Al in nutrient solutions (pH 4.0). Genotypes were categorized into “Al‐sensitive”, “intermediate Al‐tolerant”, “Al‐tolerant”, and SC 283 (an Al‐tolerant standard). As Al increased, shoot and root dry matter (DM), net main axis root length (NMARL), and total root length (TRL) became lower than controls (0 Al). Aluminum toxicity and/or nutrient deficiency symptoms become more severe, and shoot to root DM ratios and specific RL (TRL/root DM) values also changed as Al in solution increased. Root DM had greater changes among genotypes than shoot DM, and NMARL at 400 μM Al, and TRL at 200 μM Al had greater differences among genotypes than root DM, ratings for toxicity and/or deficiency symptoms, and other DM and RL traits. The wide differences among genotypes for NMARL and TRL could be used more effectively to evaluate sorghum genotypes for tolerance to Al toxicity than the other growth traits.