Assessment of the Zn status of chickpea by plant analysis

Chickpea (Cicer arietinum L.) is extensively grown in areas where soils are deficient in zinc (Zn). To determine the response of chickpea to Zn nutrition and to diagnose Zn status in plant tissue, two glasshouse experiments were conducted using Zn-deficient siliceous sandy soil. In Experiment 1, two genotypes of desi chickpea (Dooen and Tyson) were grown at five Zn levels (0, 0.04, 0.2, 1.0 and 5.0 mg kg^-1 of soil). After 4 weeks, no difference in growth and no visible symptoms of Zn deficiency were detected. After 6–8 weeks of growth, chlorosis of younger leaves and stipules occured in the Zn₀ treatment, with shoot dry weight being only 24% of that recorded at the highest Zn level. Root growth increased from 0.52 g/plant when no Zn was applied to 1.04 g/plant in the treatment with 0.2 mg Zn kg^-1 of soil; no response to further increase of Zn fertilization occurred. Zinc concentration in the whole shoot increased significantly with increased in Zn application. The critical Zn concentration in the shoot tissue, associated with 90% of maximum growth, was 20 mg kg^-1 for both genotypes at flowering stage.In the second experiment, two genotypes of desi chickpea (Tyson and T-1587) were grown at three Zn levels (0, 0.5 and 2.5 mg kg^-1 of soil) under two moisture regimes (field capacity 12% w/w, and water stress 4% w/w). Shoot growth was influenced by both Zn supply and water stress. The effect of water stress was severe in the 0.5 and 2.5 mg Zn treatments where shoot dry matter was reduced 52 and 46%, respectively. T-1587 was less sensitive to Zn deficiency and produced higher shoot dry weight than Tyson in the Zn₀ treatment. Zinc concentration in shoots increased from 5 mg kg^-1 when no Zn was applied to 40 mg kg^-1 at the highest Zn level. The critical Zn concentration in shoots was 21 mg kg^-1.The results of the two experiments showed that the critical concentration for Zn did not differ amongst the three cultivars used and was not affected by soil moisture. Similar studies should be undertaken with a wider number of genotypes to discover if a critical concentration of 20–21 mg kg^-1 in the shoot can be used to diagose the Zn status of chickpea genotypes.     

Distribution of selected elements within flax plants as affected by FeEDDHA

Summary Flax growing on a calcareous soil in the greenhouse developed Mn toxicity symptoms. The toxicity was eliminated by application of 2 ppm FeEDDHA-Fe. FeEDDHA had major effects on distribution of Mn, Zn, Fe and P among selected plant parts. Application of the chelate reduced Mn concentration in older leaves, the tissue most susceptible to Mn toxicity, associated stem tissue, plant tops, and roots from 2295 to 133 ppm, 62 to 7 ppm, 550 to 34 ppm, and 42 to 34 ppm, respectively. Analysis of older leaves is recommended for diagnosing Mn toxicity in flax.FeEDDHA reduced Zn concentration in plant tops and this was chiefly reflected in greatly reduced leaf concentrations, especially in older leaves. FeEDDHA increased plant Fe concentration and the effect was greatest in root and older leaf tissues. The overall effect of FeEDDHA on P concentration was small but large increases occurred in younger leaf tissue due to application of the chelate. Relative distributions of K, Na, Ca, and Mg among plant parts were only slightly affected by FeEDDHA.     

Differential reactions of wheat and pea genotypes to root inoculation with growth-affecting rhizosphere bacteria

Spring wheat (Triticum aestivum L.) and pea (Pisum spp.) genotypes were tested for reaction to root inoculation with rhizosphere bacteria affecting plant growth. Plant response was studied in greenhouse experiments after treatment of seedlings with bacteria suspended in nutrient broth. Significant genotype variation was found in both wheat and pea in terms of shoot dry weight and severity of bacteria-induced leaf symptoms. For most bacterial isolates tested, there was good correlation between ratings of leaf symptoms 7 to 14 days after inoculation and growth inhibition measured after four weeks. Interactions between isolates and plant genotypes were significant in both wheat and pea (P=0.0024 and 0.0001, respectively), but genotypes with sensitivity or tolerance to most isolates could be distinguished. In an outdoor pot experiment, two of the bacterial isolates caused delayed plant development and differential decreases in grain yield of wheat genotypes. The hypothesis that the reaction of wheat genotypes to the tested becteria was related to their influence on bacterial establishment in the rhizosphere could not be substantiated.     

Chickpea genotypes differ in their sensitivity to Zn deficiency

Zinc (Zn) deficiency is common in most of the chickpea growing areas of the world and growing Zn-efficient genotypes on Zn-deficient soil is a benign approach of universal interest. Response of 13 chickpea genotypes (10 desi and 3 kabuli) to Zn nutrition was studied in a pot experiment under glasshouse conditions. Plants were grown in a Zn-deficient siliceous sand for 6 weeks and fertilized with 0 (Zn–) and 2.5 mg Zn per kg soil (Zn+). When grown with no added Zn, Zn deficiency symptoms (chlorosis of younger leaves and stipules followed by necrosis of leaf margins) appeared 3–4 weeks after planting and were more apparent in cultivars Tyson, Amethyst and Dooen than Kaniva and T-1587. Zn deficiency reduced shoot growth, but it was less affected in breeding lines T-1587 and CTS 11308 than cultivars Tyson, Dooen, Amethyst and Barwon. Among all genotypes, Tyson produced the lowest root dry weight in Zn– treatment. Zinc efficiency based on shoot dry weight showed marked differences among genotypes; breeding lines CTS-60543, CTS-11308 and T-1587 were 2-fold more Zn-efficient than cultivars Tyson and Dooen. A higher Zn accumulation per plant and higher Zn uptake per g. of root dry weight were recorded in T-1587 and CTS-11308 when compared with Tyson. Root:shoot ratio was increased and proportionally more Zn was transported to the shoot when the soil was deficient. Cultivars that were very sensitive to Zn deficiency tended to have their root:shoot ratio increased by Zn deficiency more than less sensitive cultivars. The insensitive lines T-1587 and CTS-11308 transported more than 70% of the total absorbed Zn to the shoot. It is concluded that chickpea genotypes vary in their sensitivity to Zn deficiency. Advanced breeding lines T-1587 and CTS-11308 are relatively more Zn-efficient compared with Australian chickpea cultivar Tyson. Zn efficiency in chickpea genotypes is probably related to an efficient Zn absorption coupled with a better root to shoot transport.     

供锌条件下碳酸钙对小麦幼苗生长和锌吸收的影响

通过营养液培养试验,研究了供Zn条件下添加CaCO₃对3种基因型冬小麦（远丰998、中育6号、小偃22）幼苗生长及Zn吸收的影响.结果表明,供Zn和添加CaCO₃对小麦幼苗生长量和根冠比均无显著性影响,3种基因型小麦间亦无显著性差异;添加CaCO₃诱发了小麦叶片失绿黄化.无论供Zn还是不供Zn,添加CaCO₃对3种基因型小麦根、茎、叶各部分的Zn含量及累积量均无显著性影响;与不供Zn处理相比,供Zn会大幅度地提高根、茎、叶的Zn含量和累积量,供Zn使3种基因型小麦植株Zn含量分别增加80.0%、104.8%和139.6%,缺Zn敏感型小麦远丰998植株Zn含量和累积量的增加幅度远小于不敏感型小麦中育6号和小偃22.供Zn和添加CaCO₃对小麦幼苗根、茎、叶中P含量均无显著影响,但远丰998小麦根、茎、叶3部分的P含量均明显低于其它两种非敏感型小麦.供Zn使小麦根、茎、叶3部分的P/Zn大幅度降低,添加CaCO₃也使P/Zn呈现降低的趋势.不供Zn条件下添加CaCO₃能诱发小麦失绿黄化,但Zn吸收量未降低.表明在水培条件下,高含量CaCO₃对小麦Zn吸收并未产生明显的抑制作用.     

Differential response of rye,triticale, bread and durum wheats to zinc deficiency in calcareous soils

Field and greenhouse experiments were carried out to study the response of rye (Secale cereale L. cv. Aslim), triticale (× Triticosecale Wittmark. cv. Presto), two bread wheats (Triticum aestivum L, cvs. Bezostaja-1 and Atay-85) and two durum wheats (Triticum durum L. cvs. Kunduru-1149 and C-1252) to zinc (Zn) deficiency and Zn fertilization in severely Zn-deficient calcareus soils (DTPA-Zn=0.09 mg kg^-1 soil). The first visible symptom of Zn deficiency was a reduction in shoot elongation followed by the appearance of whitish-brown necrotic patches on the leaf blades. These symptoms were either absent or only slight in rye and triticale, but occurred more rapidly and severely in wheats, particularly in durum wheats. The same was true for the decrease in shoot dry matter production and grain yield. For example, in field experiments at the milk stage, decreases in shoot dry matter production due to Zn deficiency were absent in rye, and were on average 5% in triticale, 34% in bread wheats and 70%, in durum wheats. Zinc fertilization had no effect on grain yield in rye but enhanced grain yield of the other cereals. Zinc efficiency of cereals, expressed as the ratio of yield (shoot dry matter or grain) produced under Zn deficiency compared to Zn fertilization were, on average, 99% for rye, 74% for triticale, 59% for bread wheats and 25% for durum wheats.These distinct differences among and within the cereal species in susceptibility to Zn deficiency were closely related to the total amount (content) of Zn per shoot, but not with the Zn concentrations in shoot dry matter. For example, the most Zn-efficient rye and the Zn-inefficient durum wheat cultivar C-1252 did not differ in shoot Zn concentration under Zn deficiency, but the total amount of Zn per whole shoot was approximately 6-fold higher in rye than the durum wheat. When Zn was applied, rye and triticale accumulated markedly more Zn both per whole shoot and per unit shoot dry matter in comparison to wheats.The results demonstrate an exceptionally high Zn efficiency of rye and show that among the cereals studied Zn efficiency declines in the order rye>triticale>bread wheat>durum wheat. The differences in expression of Zn efficiency are possibly related to a greater capacity of efficient genotypes to acquire Zn from the soil compared to inefficient genotypes.     

冶炼厂污灌区土壤铜和锌污染与土壤酶活性

通过对冶炼厂污灌区土壤和水稻中Cu、Zn含量分析以及土壤酶活性的测定,研究了距冶炼厂不同距离土壤Cu、Zn含量状况、水稻对它们的吸收和分配以及土壤酶活性的变化.结果表明,冶炼厂造成了周围农田土壤的Cu、Zn污染,其中Cu污染较严重,距离冶炼厂100 m处的全量和提取态Cu分别为182.4和81.91 mg·kg^-1,是对照的10.3和3倍.污灌区水稻各器官Cu、Zn的分布规律是,Cu:根＞茎叶＞米;Zn:茎叶＞根＞米.Zn在水稻体内的移动能力大于Cu,Cu主要累积在水稻根部,根可作为一种屏障阻碍Cu向地上部分迁移,使地上部分免受其害.水稻茎叶Cu含量和土壤中Cu的浓度密切相关.对蔗糖酶、过氧化氢酶和脲酶活性测定表明,脲酶活性变化最显著,其活性与土壤中Cu的浓度显著相关,建议用脲酶活性作为污灌区Cu污染指标.     

Effect of the Duration of the Vegetative Phase on Shoot Growth, Development and Yield in Pearl Millet (Pennisetum americanum (L.) Leeke)

Craufurd, P. Q. and Bidinger, F. R. 1988. Effect of the durationof the vegetative phase on shoot growth, development and yieldin pearl millet (Pennisetum americanum (L.) Leeke).–J.exp. Bot. 38: 124–139 The duration of the vegetative phase (DVP) in millet, whichis the major cause of variation in the crop duration, has markedeffects on the number of productive tillers per plant and onmainshoot (MS) and tiller grain yield. Daylength extensionswere used to vary the DVP and the effect on factors affectingpanicle (tiller) number per plant and panicle yield examinedin millet hybrid 841A x J104, grown in the field at Hyderabad,India. Tiller appearance, shoot leaf appearance and leaf area,and stem and panicle growth, in both MS and primary tillers(PTs), were monitored at frequent intervals over the season.At maturity grain yield per shoot was measured The concept of thermal time was used to describe shoot development.The rates of tiller appearance and shoot leaf appearance werelinearly related to thermal time and were not affected by DVPtreatments. The duration of the growth phase from panicle initiationto flowering (GS2) and from flowering to maturity (GS3) was320 and 390 degree days (°Cd), respectively. There was nodifference in rates of leaf or tiller appearance or developmentbetween MS and PTs. Tiller appearance, tiller leaf appearanceand tiller apical development all ceased at the same time inthe later initiated PTs, approximately 550 °Cd from sowing,shortly after rapid stem growth had begun. Tillers that didnot survive were all vegetative or in the early stages of reproductivedevelopment at this time The rate of accumulation of dry matter per plant was similarin all DVP treatments, but in the longer DVP treatments a greaterproportion of the dry matter was partitioned to the MS. Mainshootstem and panicle growth rates were increased by a longer DVP,as was grain yield on the MS, and these were related to increasedMS leaf area. Concurrently, growth rates and yields in laterinitiated tillers were reduced in relation to their leaf areas.Stem growth rate was proportionately increased more than paniclegrowth rate in the longer DVP treatments and this, combinedwith a longer duration of stem growth, resulted in greater stemdry matter at maturity and, therefore, in reduced harvest index.     

Genotypic variation of the response to cadmium toxicity in Pisum sativum L

This work evaluates the (cor-)relations between selected biochemical responses to toxic Cd and the degree of Cd sensitivity in a set of pea genotypes. Ten genotypes were analysed that differ in their growth response to Cd when expressed as root or shoot tolerance indices (TIs). Concentrations of non-protein thiols (NPTs) and malondialdehyde (MDA), activity of chitinase, peroxidase (POX), and catalase significantly increased in all pea genotypes treated with Cd. Cd-sensitivity of genotypes was correlated with relative increases in MDA concentration as well as activities of chitinase and POX, suggesting similar Cd stress effects. Activities of ascorbate peroxidase (APX) decreased, but concentrations of glutathione (GSH) increased in the less Cd-sensitive genotypes. Differences in root and leaf contents of Cd revealed no correlation with TI, metabolic parameters, and enzyme activities in Cd-treated plants, respectively, except that shoot Cd concentration positively correlated with shoot chitinase activity. Toxic Cd levels inhibited uptake of nutrient elements such as P, K, S, Ca, Zn, Mn, and B by plants in an organ- and genotype-specific manner. Cd-sensitivity was significantly correlated with decreased root Zn concentrations. The results show both similarities, as well as distinct features, in Cd toxicity expression in genotypes of one species, suggesting that independent and multi-factorial reactions modulate Cd sensitivity on the low-tolerance level of plants. The study illustrates the biochemical basis of earlier detected genotypic variation in Cd response.     

Genetic variation in pea (Pisum sativum L.) demonstrates the importance of root but not shoot C/N ratios in the control of plant morphology and reveals a unique relationship between shoot length and nodulation intensity

Nodule numbers are regulated through systemic auto‐regulatory signals produced by shoots and roots. The relative effects of shoot and root genotype on nodule numbers together with relationships to organ biomass, carbon (C) and nitrogen (N) status, and related parameters were measured in pea (Pisum sativum) exploiting natural genetic variation in maturity and apparent nodulation intensity. Reciprocal grafting experiments between the early (Athos), intermediate (Phönix) and late (S00182) maturity phenotypes were performed and Pearson's correlation coefficients for the parameters were calculated. No significant correlations were found between shoot C/N ratios and plant morphology parameters, but the root C/N ratio showed a strong correlation with root fresh and dry weights as well as with shoot fresh weight with less significant interactions with leaf number. Hence, the root C/N ratio rather than shoot C/N had a predominant influence on plant morphology when pea plants are grown under conditions of symbiotic nitrogen supply. The only phenotypic characteristic that showed a statistically significant correlation with nodulation intensity was shoot length, which accounted for 68.5% of the variation. A strong linear relationship was demonstrated between shoot length and nodule numbers. Hence, pea nodule numbers are controlled by factors related to shoot extension, but not by shoot or root biomass accumulation, total C or total N. The relationship between shoot length and nodule numbers persisted under field conditions. These results suggest that stem height could be used as a breeding marker for the selection of pea cultivars with high nodule numbers and high seed N contents.     

Response of Contrasting Rice Genotypes to Zinc Sources under Saline Conditions

Abiotic stresses are among the major limiting factors for plant growth and crop productivity. Among these, salinity is one of the major risk factors for plant growth and development in arid to semi-arid regions. Cultivation of salt tolerant crop genotypes is one of the imperative approaches to meet the food demand for increasing population. The current experiment was carried out to access the performance of different rice genotypes under salinity stress and Zinc (Zn) sources. Four rice genotypes were grown in a pot experiment and were exposed to salinity stress (7 dS m⁻¹), and Zn (15 mg kg⁻¹ soil) was applied from two sources, ZnSO₄ and Zn-EDTA. A control of both salinity and Zn was kept for comparison. Results showed that based on the biomass accumulation and K⁺/Na⁺ ratio, KSK-133 and BAS-198 emerged as salt tolerant and salt sensitive, respectively. Similarly, based on the Zn concentration, BAS-2000 was reported as Zn-in-efficient while IR-6 was a Zn-efficient genotype. Our results also revealed that plant growth, relative water content (RWC), physiological attributes including chlorophyll contents, ionic concentrations in straw and grains of all rice genotypes were decreased under salinity stress. However, salt tolerant and Zn-in-efficient rice genotypes showed significantly higher shoot K⁺ and Zn concentrations under saline conditions. Zinc application significantly alleviates the harmful effects of salinity by improving morpho-physiological attributes and enhancing antioxidant enzyme activities, and the uptake of K and Zn. The beneficial effect of Zn was more pronounced in salt-tolerant and Zn in-efficient rice genotypes as compared with salt-sensitive and Zn-efficient genotypes. In sum, our results confirmed that Zn application increased overall plant’s performance under saline conditions, particularly in Zn in-efficient and tolerant genotypes as compared with salt-sensitive and Zn efficient rice genotypes.     

Distribution and remobilization of Zn and Mn during grain development in wheat

Wheat (Triticum aestivum cv. Aroona) was grown in siliceoussand with essential nutrients for unlimited growth except forthe following treatments: controls (sufficient Zn and Mn), lowMn (sufficient Zn) and low Zn (sufficient Mn) until anthesis.Replicate plants were harvested at anthesis; the remaining plantswere transferred to a chelate-buffered nutrient solution containingall essential nutrients except Zn and Mn to allow monitoringof the remobilization of existing Zn and Mn reserves withinthe plant. These plants were harvested 14 d post-anthesis andat grain maturity. At each harvest plants were separated intoindividual components. There were no growth differences between any of the treatmentsat the three harvests. Large amounts of Zn and Mn found in theroots and stems at anthesis were rapidly depleted during graindevelopment. The Zn content of the leaves increased from anthesisto 14 d post-anthesis, but then declined. The Mn content ofthe leaves increased throughout grain development in the controlswhilst remaining constant in the plants pre-grown at low Mn.The Zn and Mn content of the glumes, palea and lemma rose inthe controls from anthesis to 14 d post-anthesis; thereafterZn content declined but Mn content continued to increase. TheZn and Mn content of the grain rose sharply toward grain maturity.We conclude that Mn was not remobil-ized from the leaves ofwheat during grain development. Zinc was remobilized from theleaves, especially the flag leaf and from the leaves of thelow Zn plants. The post-anthesis accumulation of Zn and Mn withinthe glumes will be discussed in relation to the transport pathwaythat Zn and Mn use to enter the developing seed. Key words: Zinc, manganese, wheat, distribution, remobilization     

Effect of zinc,phosphorus and nitrogen on tryptophan concentration in rice grains grown on limed and unlimed soils

Summary The effects of Zn, P, N and CaCO₃ on tryptophan concentration in rice grain were studied in greenhouse at Haryana Agricultural University. Zinc application upto 20 ppm increased tryptophan concentration in rice grain. Zn-EDTA gave highest increase followed by ZnSO₄ and then ZnO. Liming at the rate of 4 and 8 per cent decreased tryptophan concentration significantly. Phosphorus application upto 100 ppm also decreased tryptophan significantly but Zn in combination with P increased tryptophan and overcame negative effect of P. Nitrogen application upto 120 ppm increased tryptophan concentration. There was positive interaction between Zn and N. Ammonium sulphate gave highest tryptophan followed by ammonium nitrate and then urea. The tryptophan concentration ranged between 766 ppm and 2011 ppm in paddy grain. The lowest tryptophan concentration was in the plants treated with 8 per cent lime in absence of added Zn and highest with 10 ppm Zn through Zn-EDTA. Department of Soils.     

From Flooded to Aerobic Conditions in Rice Cultivation: Consequences for Zinc Uptake

Scarcity of water causes a shift from flooded to aerobic conditions for rice production in zinc deficient areas in Northern China. This shift alters soil conditions that affect zinc availability to the crop. This paper concerns the effect of aerobic compared to flooded conditions on crop biomass production, grain yield and zinc content. A field experiment was done with six rice genotypes (Oryza sativa L.) grown on a calcareous soil, both with (23 kg Zn ha⁻¹) and without Zn fertilization. Sampling was conducted at tillering and physiological mature stage. Zn concentration in the shoots was significantly lower at both stages in plants grown in the aerobic field. At maturity, Zn uptake, biomass production, grain yield and Zn-harvest index [grain Zn/(shoot + grain Zn)] were lower under aerobic cultivation. Rice genotypes including aerobic rice and lowland rice differ in degree of response to low Zn supply. A twofold difference was found among aerobic genotypes in grain yield and Zn uptake. Also Zn-harvest index varied significantly. Zn application affected neither grain yield nor grain Zn content, although it significantly improved biomass production in both systems in most genotypes. These results demonstrate that introduction of aerobic rice systems on calcareous soils may increase Zn deficiency problems.     

Zn fertilization improves water use efficiency,grain yield and seed Zn content in chickpea

In a number of the major chickpea-growing areas in the world, rainfed crops of chickpeas are often grown on soils with low available zinc (Zn). Consequently, chickpea crops can be challenged by soil water deficits and Zn deficiency coincidentally during the growing season. The interaction between these stresses was examined in two glasshouse experiments using genotypes differing in Zn efficiency. Water stress was imposed during podding. Increasing the level of Zn resulted in large and significant increases in vegetative growth up to podding. Applying Zn increased grain yields when the plants were well watered, but not under water stress, except for the Zn-efficient and drought-resistant genotype ICC-4958. Harvest indices were generally reduced as the supply of Zn and water increased. Applying Zn increased water use and water use efficiency of chickpea. Yields were reduced by water stress, largely due to fewer pods set per plant. Losses from water stress were greatest at the highest level of Zn, which was attributed to the limited soil volume afforded by the pots and the rapid development of stress in the larger plants grown at adequate levels of Zn. However, at each level of Zn, the loss in yield from water stress tended to be less in a Zn-efficient genotype. The major factor determining the distribution of Zn in the plant was the supply of Zn, while differences due to water stress and genotype were relatively small. Two-thirds of the Zn present in the plant at maturity was accumulated after the start of podding and this was little affected by water stress. The proportion of Zn in the roots of Zn-deficient plants was less than that in Zn-adequate plants. As the Zn supply increased, Zn accumulation was higher in leaves than in the stem and reproductive parts, due to combined effect of both higher Zn concentration and higher dry matter. At maturity, senesced leaves and pod walls had relatively lower concentrations of Zn compared to leaves and pods at the start of podding in all Zn treatments. In contrast, the Zn content in the stem either increased or remained unchanged. At maturity, Zn accumulation in plant organs generally increased with increasing Zn supply, but the largest proportion of Zn was found in the seeds, which is a beneficial nutritional trait for human nutrition.     

Production of a Host-Specific Toxin by Germinating Spores of Alternaria tenuissima Causing Leaf Spot of Pigeon Pea

Production of a host-specific toxin by Alternaria tenuissima , the cause of pigeon pea leaf spot, was investigated in spore-germination fluids (SGF). The SGF selectively induced necrosis on pigeon pea leaves in a deteched leaf assay. Necrotic lesions were observed when a toxin from SGF was applied onto detached young leaves of the pigeon pea cultivar Bahar at concentration as low as 5 ng/ml. The resistant line Tanzania and nonhosts tolerated at least 20,000 times higher concentration of the toxin. The differential activity of the toxin on hosts and nonhosts of the fungus, as well as on susceptible and resistant cultivars or lines, suggested host-specific property of the toxin. At a concentration of 10 ng/ml, the toxin induced susceptibility of pigeon pea leaves to a non-pathogenic isolate of Alternaria alternata. The toxin possibly plays a role as a disease determinant of A. tenuissima , because the toxin was released from germinating spores as early as 3 h of incubation andthe, amount detected within 9 h was about 6 times of the concentration required for necrotic toxicity.     

Effects of elevated carbon dioxide and ozone on the growth and yield of spring wheat (Triticum aestivum L.)

Spring wheat cv. Minaret was grown under three carbon dioxide(CO₂) and two ozone (O₃) concentrations from seedling emergenceto maturity in open-top chambers. Under elevated CO₂ concentrations,the green leaf area index of the main shoot was increased, largelydue to an increase in green leaf area duration. Biomass increasedlinearly in response to increasing CO₂ (ambient, 550 and 680ppm). At anthesis, stem and ear dry weights and plant heightwere increased by up to 174%, 5% and 9 cm, respectively, andbiomass at maturity was 23% greater in the 680 ppm treatmentas compared to the ambient control. Grain numbers per spikeletand per ear were increased by 0.2 and 5 grains, respectively,and this, coupled with a higher number of ears bearing tillers,increased grain yield by up to 33%. Exposure to a 7 h daily mean O₃ concentration of 60 ppb inducedpremature leaf senescence during early vegetative growth (leaves1–7) under ambient CO₂ concentrations. Damage to the mainshoot and possible seedling mortality during the first 3 weeksof exposure altered canopy structure and increased the proportionof tillers 1 and 2 which survived to produce ears at maturitywas increased; as a result, grain yield was not significantlyaffected. In contrast to the older leaves, the flag leaf (leaf8) sustained no visible O₃ damage, and mean grain yield perear was not affected. Interactions between elevated CO₂ andO₃ influenced the severity of visible leaf damage (leaves 1–7),with elevated CO₂ apparently protecting against O₃-induced prematuresenescence during early vegetative growth. The data suggestthat the flag leaf of Minaret, a major source of assimilateduring grain fill, may be relatively insensitive to O₃ exposure.Possible mechanisms involved in damage and/or recovery are discussed. Key words: Carbon dioxide, ozone, spring wheat (cv. Minaret), leaf damage, tiller, yield     

Differentiation Among Bean Leafroll Virus Susceptible and Resistant Lentil and Faba Bean Genotypes on the Basis of Virus Movement and Multiplication

Systemic movement of Bean leafroll virus (BLRV) in susceptible and resistant lentil and faba bean genotypes was studied using plants grown in a plastic house. All the plants studied were inoculated with BLRV by viruliferous pea aphids (Acyrthosiphon pisum). Five plants/genotype of lentil and faba bean were harvested, respectively, at 3, 6, 9, 12 and 18 days and 1, 2, 3, 4 and 5 weeks after inoculation. Each plant was split into growing point, stem, stem base and root, and each was tested using tissue blot immunoassays (TBIA). Virus concentration in each section was estimated using a 0–3 score and a relative TBIA value was estimated accordingly for each genotype. In susceptible lentil genotypes (ILL 8063 and ILL 2581), BLRV was present in low concentrations in the growing point 3 days after inoculation and in high concentrations in all parts of the plant after 6 days. By contrast, the virus was not detected in the highly resistant genotype (ILL 74) until 18 days after inoculation. In the faba bean genotypes studied, BLRV was detected in high concentrations in all parts of the highly susceptible genotype (Fiord) 1 week after inoculation but only after 3 weeks in resistant genotypes (e.g. BPL 5274), but was not detected in the highly resistant genotypes (BPL 5278 and BPL 5279) 5 weeks after inoculation. The replication and systemic movement of BLRV was thus slower in resistant genotypes than in susceptible genotypes. Moreover, the use of TBIA scores clearly and easily differentiated resistant and susceptible genotypes. Our results suggest that BLRV movement and multiplication can be useful criteria when differentiating resistant from susceptible genotypes. In addition, undertaking the preliminary screening in a plastic house requires less space than direct planting in the field.     

Alfalfa genotypes differ in their ability to tolerate zinc deficiency

Response of 13 alfalfa (Medicago sativa L.) genotypes to varied Zn supply (+Zn: 2 mg kg⁻¹ soil, −Zn: no added Zn) was studied in a pot experiment under controlled environmental conditions. Plants were grown for four weeks in a Zn-deficient siliceous sandy soil. Plants grown at no added Zn showed typical Zn deficiency symptoms i.e. interveinal chlorosis of leaves, yellowish-white necrotic lesions on leaf blades, necrosis of leaf margins, smaller leaves and a marked reduction in growth. There was solute leakage from the leaves of Zn-deficient plants, while no solute leakage from Zn-sufficient plants. The ratios of P:Zn, Fe:Zn, Cu:Zn and Mn:Zn in Zn-deficient plants were extremely high compared with Zn-sufficient plants indicating disturbance of P:Zn, Fe:Zn, Cu:Zn and Mn:Zn balance within plant system by Zn deficiency. Genotypes differed markedly in Zn efficiency based on shoot dry matter production. Alfalfa genotypes also differed markedly in P:Zn ratio, Cu:Zn ratio and Fe:Zn ratio under —Zn treatment. The shoot dry weight, shoot:root ratio, chlorophyll content of fresh leaf tissue, solute leakage from the leaves, Zn uptake and distribution of Zn in shoots and roots were the most sensitive parameters of Zn efficiency. Zn-efficient genotypes had less solute leakage but higher shoot:root ratio and higher Zn uptake compared with Zn-inefficient genotypes. Under —Zn treatment, Zn-inefficient genotypes had less Zn partitioning to shoots (33–37%) and more Zn retained in roots (63–67%), while Zn-efficient genotypes had about equal proportions of Zn in roots (50%) and shoots (50%). This revised version was published online in June 2006 with corrections to the Cover Date.     

Tolerance of wheat and pea to boron in irrigation water

In a micro-plot experiment 1.5 ppm boron in the irrigation water was toxic for wheat. Its concentration in the soil solution increased to 1.53 ppm and in the plant tissue to 58 ppm. In pea plants 4 ppm B in the irrigation water was toxic with 2.00 ppm soil solution B and 213 ppm tissue B. Nitrogen in both species increased significantly and calcium decreased with the increase in B in irrigation water. The yield of wheat grain declined by 13, 20 and 32 per cent at the 4.0, 6.0 and 8.0 ppm B respectively. The yield of straw and grains of pea declined by 31, 56 and 41, 56 per cent at 6.0 and 8.0 ppm B levels respectively. Thus tolerance to B in irrigation water was between 3.0 and 4.0 ppm for wheat and 4.0 and 6.0 ppm for pea.