Root Dry Matter Production Research Articles

Exigência a boro em cultivares de soja

O conhecimento quanto à exigência a boro de genótipos da soja pode ser relevante para: recomendações de corretivos e fertilizantes, recomendação de cultivares e programas de melhoramento. O objetivo deste trabalho foi estudar a resposta de cultivares de soja à adição de doses de boro em solução nutritiva. O experimento foi realizado em casa de vegetação do Instituto Agronômico de Campinas - IAC, Campinas (SP). Foram estudados quatro cultivares de soja (IAC-1, IAC-8, IAC-15 e IAC-17) e cinco doses de boro (0,0; 0,05; 0,20; 0,80 e 2,00 mg L-1 de B), utilizando-se delineamento em blocos ao acaso, em esquema fatorial com cinco repetições. As plantas foram avaliadas quanto aos sintomas de deficiência à toxidez, produção de matéria seca, altura das plantas, teores críticos de B nas folhas, B absorvido pela planta e teores de P, K, Ca e Mg. As plantas foram colhidas no início do florescimento para determinação da massa da matéria seca e teores de nutrientes. Os teores limites de B nas folhas para a deficiência variaram de 25 a 30 mg kg-1, mostrando diferenças entre os cultivares nesta susceptibilidade. O sintoma inicial de toxidez foi observado a partir da dose de 0,8 mg L-1 de B na solução, cujo teor correspondente nas folhas foi de 83 mg kg-1 de B (média dos cultivares), enquanto o acúmulo máximo de matéria seca total ocorreu para concentrações na solução estimadas entre 0,1 e 0,2 mg L-1. A severidade dos sintomas visuais variou entre cultivares dentro do mesmo tratamento, indicando diferentes tolerâncias ao excesso do nutriente. Assim, quanto aos sintomas de deficiência e de toxidez, o cv. IAC-1 foi o mais susceptível à deficiência e à toxidez de B, e o cv. IAC-17 foi, aparentemente, o mais tolerante ao excesso de B. Os cvs. IAC-8 e o IAC-15 acumularam as maiores quantidades de B, mesmo nos tratamentos com baixa concentração de B na solução. Os teores de P, K, Ca e Mg nas folhas não variaram significativamente entre os tratamentos que receberam boro (0,05 a 2,0 mg L-1), com exceção das plantas com deficiência severa.

Teores de carboidratos não-estruturais, nitrogênio total e peso de raízes em Coastcross-1 (Cynodon dactylon (L.) Pers) pastejado por ovinos

O experimento foi realizado no período de outubro de 1997 a abril de 1998, com o objetivo de avaliar os teores de carboidratos não-estruturais (CHO), nitrogênio total (NT) e produção de raízes em pastagem de Coastcross-1 (Cynodon dactylon (L.) Pers), em quatro níveis de resíduo de matéria seca (RMS: 1978, 2130, 2545 e 3857 kg de MS/ha), sob pastejo contínuo e lotação variável. O delineamento experimental utilizado foi inteiramente casualizado, com duas repetições. As avaliações dos teores de CHO e NT foram estudadas nas raízes e base do colmo, em função dos níveis de resíduo de matéria seca (RMS) e do tempo (dias) do experimento. Os resultados observados evidenciam que os teores de CHO nas raízes e a porcentagem de NT na base de colmo não foram influenciados pelos níveis de RMS e período de coleta. Os maiores teores de CHO na base do colmo foram encontrados a partir do resíduo de 2545 kg de MS/ha, e no tempo houve constante adaptação às condições de pastejo. O teor de CHO foi superior na base do colmo, comparada às raízes. A porcentagem de NT nas raízes diminuiu até o nível de 2545 kg de MS/ha. A produção de matéria seca de raízes aumentou, à medida que aumentou os RMS, ocorrendo declínio em relação ao período de coleta.

Cowpea reactions to Alectra vogelii I: : effect on growth

Field trials were conducted in 1993, 1994 and 1995 wet seasons to determine the effect of Alectra vogelii on the vegetative growth of 16 cowpea varieties. This include 11 resistant varieties: IT81D-985, IT81D-994, IT89KD-245-1, TN93-80, TN121-80, IT90K-76, IT90K-59, IT86D-534, IT86D-843, B301 and IT89KD-245, two tolerant varieties: KANO 1696 and VITA 3 and three susceptible varieties: SAMPEA 7, TVX 3236 and IT82D-849. The growth of A. vogelii on each of the cowpea varieties was also evaluated. Cowpea varieties Tvx 3236, VITA 3, SAMPEA 7, KANO 1696, IT89KD-245 and IT82D-849 had higher Alectra infestation than the other varieties in the study. Alectra infestation generally showed a high tendency to stimulate root and shoot dry matter production of most cowpea varieties studied at 5 WAP, especially in 1993 and 1994. Generally, more cowpea varieties had the root and shoot dry matter production reduced at 9 WAP, with greater reduction in the late planted crop and heavily infested cowpea plants as observed in 1993 and 1995, respectively. The root dry weight of varieties IT89KD-245, IT90K-76 and IT90K-59 in 1993 and 1994 and IT81D-994 and B301 in 1994 and 1995 and TN93-80 in 1993 and 1995 was increased at 9 WAP, whereas that of SAMPEA 7 and IT86D-843 was reduced at 9 WAP in all the trials. Irrespective of sowing date and level of infestation, the adverse effect of Alectra infestation on cowpea shoot growth was more apparent between 7 and 9 WAP — a period of flower initiation and first phase of pod development. Generally, Alectra infestation showed a high tendency to reduce the leaf area of most of the cowpea varieties in at least two of the sampling dates. The root nodule formation in both resistant and susceptible cowpea varieties was inhibited by Alectra infestation. It reduced the root nodule count of varieties IT81D-985, IT89KD-245-1, IT90K-76, TN93-80, KANO 1696 and SAMPEA 7 in 1994 and IT82D-849 in 1995 at all the sampling dates in each trial. This study showed that the devastation of cowpea grain yield by Alectra could be attributed to the reduced root nodulation, root and shoot growth exhibited by susceptible varieties at stages of vegetative growth.

ÍNDICES DE EFICIÊNCIA DE VARIEDADES LOCAIS E MELHORADAS DE MILHO AO FÓSFORO

Avaliaram-se dez variedades locais e melhoradas de milho (Zea mays L.) a fim de verificar sua eficiência ao fósforo (P) em solução nutritiva e em campo. Em solução nutritiva, o experimento foi realizado no Instituto Agronômico, Campinas (SP), durante 1995-1996; o delineamento adotado foi o de em blocos ao acaso, com cinco repetições. Os tratamentos, dispostos em fatorial, constituíram-se de três concentrações de P (0,0645; 0,129 e 0,258 mmol.L-1) e dez variedades de milho. Em campo, o experimento foi instalado na Embrapa Agrobiologia, em Seropédica (RJ), durante 1998-1999, em blocos ao acaso, com seis repetições, utilizando-se a dose de 44 kg.ha-1 de P (100 kg.ha-1 de P2O5) e as mesmas variedades de milho utilizadas em solução nutritiva: Caiano de Sobrália, Carioca, Antigo Maya, Catetão, Pedra Dourada, Nitrodente, Sol da Manhã (BRS Sol da Manhã), BR 105, BR 106 e BR 107. Determinaram-se a produção de matéria seca e/ou de grãos, conteúdo de P e índices de eficiência nas plantas de ambos os experimentos. As variedades Nitrodente e BR 106 acumularam mais matéria seca na parte aérea em solução nutritiva e apresentaram maiores produções de grãos e índices de eficiência em campo. Catetão, a menos produtiva em campo, mostrou uma das menores produções de matéria seca da parte aérea e de raízes em solução nutritiva. Os resultados para Pedra Dourada, BR 105, BR 107, Antigo Maya e Sol da Manhã foram intermediários e, também, comparáveis entre os ensaios de campo e em solução nutritiva. Foram exceções as variedades Carioca e Caiano, com as menores produções de matéria seca em solução nutritiva e as mais produtivas em campo.

Growth, allocation of N and carbohydrates, and stomatal conductance of greenhouse grown apple treated with prohexadione-Ca and gibberellins

SummaryPotted M.26 apple (Mahis domestica) liners were treated with the gibberellin biosynthesis inhibitor prohexadione-Ca (Apogee®) at 0 to 500 mg l”1 as a foliar spray. Apogee inhibited stem elongation, leaf formation, total leaf area and shoot dry weight, while significantly increasing specific leaf weight, root dry weight and root: shoot ratio, regardless of rate. Foliar application of gibberellin A4+7 (GA4+7) at 200 mg l”1 to Apogee-treated plants one day later reversed these effects, especially stem elongation, root dry-matter production and root: shoot ratio. Apogee increased N concentration in stems but not in leaves and roots. There was no effect on the pattern of N allocation amongst organs. GA4+7 increased leaf N concentration but decreased stem and root N concentrations compared with untreated controls, with N allocation shifting from roots to stem. Total nonstructural carbohydrates (TNC), expressed either on a concentration or content basis, increased in all parts of the Apogee-treated plants, due to increased levels of starch rather than soluble sugars, without altering allocation pattern. Conversely, GA4+7 reduced TNC levels (mainly starch levels) in all parts, with the pattern of allocation slightly shifted from roots to stem. The afternoon decline in stomatal conductance occurred earlier in the Apogee treated plants, measured 10 d after stem elongation had ceased. Starch buildup in the Apogee-treated plants appeared to be associated with this effect, suggesting an involvement of a feedback inhibition of photosynthesis in the Apogee-induced stomatal control.

Genotypic differences in effects of cadmium on growth and nutrient compositions in wheat

A solution culture study was conducted to determine the genotypic difference in the effects of cadmium (Cd) addition on growth and on the uptake and distribution of Cd and other 11 nutrients in wheat plants. Cadmium addition at a rate of 1 mg L−1 significantly reduced root and shoot dry matter production, shoot height, root length, chlorophyll content, and tillers per plant. On the average of 16 wheat genotypes used in study, Cd concentrations of Cd‐treated plants were 48.1 and 459 μg g−1 dry weight (DW) in shoots and roots, respectively, and retained 77.91% of total Cd taken up in the roots. On the whole, Cd addition reduced the concentration of sulfur (S), phosphorus (P), magnesium (Mg), molybdenum (Mo), manganese (Mn), and boron (B), and increased iron (Fe), irrespective of the plant parts. The effect of Cd on the concentration of potassium (K), calcium (Ca), and copper (Cu) differed in shoots and roots. The significant difference existed among 16 wheat genotypes in their response to Cd in terms of growth and nutrient concentrations. Genotype E81513, which showed relatively less inhibition in growth, had the lowest shoot Cd concentration and more Cd accumulation in roots, while Ailuyuang had the highest Cd concentration and accumulation in shoot with lower Cd concentration in root. The significant interaction was found between Cd treatment and genotype for all nutrient concentrations in both shoot and root, except S and Zn in root.

Growth and Carbohydrate Metabolism of Creeping Bentgrass Cultivars in Response to Increasing Temperatures

High temperature is a major factor limiting growth of creeping bentgrass (Agrostis palustris Huds.). Physiological causes of turf growth and quality decline with increasing temperature is not well understood. The objective of the study was to examine responses of growth and carbohydrate metabolisms to increasing temperatures in three creeping bentgrass cultivars. Sods of ‘Penncross’, ‘ISI‐AP‐89150’, and ‘SR 1020’ were grown in growth chambers and exposed sequentially for 20 d to each of the following temperatures: 20, 24, 30, 34, and 38°C. Evaluation and measurements were made at 10 and 20 d after each sequential temperature increase. Decreased root viability and root dry matter production of all cultivars was observed after a 10‐d exposure at 30°C and continued to decline with increasing temperatures. A decline in turf quality and leaf chlorophyll content (Chl) was observed at a 20‐d exposure to 30°C. Turf quality, Chl content, and root viability of SR 1020 were higher than those of Penncross after a 10‐d exposure at 30°C and 20 d at 34°C, and 10 d at 38°C, respectively. Canopy net photosynthetic rate (Pn) decreased with temperature in all cultivars. Dark respiration rates of whole plants (Rplant) increased with temperature up to 34°C, and then declined at 38°C. Daily carbon consumption to production ratio increased dramatically with temperature after 30°C, and Rplant exceeded Pn when temperature increased to 34 or 38°C in all cultivars. Plants grown at 30, 34, and 38°C had lower total nonstructural carbohydrate than those grown at 20 or 24°C. Results suggest that a decline in root activity of creeping bentgrass occurred before a decline in turf quality at temperatures above 30°C, and could be related to the imbalance between photosynthesis and respiration, and limited carbohydrate availability.

558 Nutrient Allocation Patterns of Lupinus havardii Wats under Different Preharvest Ca Fertilization Regimes

Lupinus havardii (Big Bend bluebonnet) is a winter annual plant indigenous to the semiarid southwestern U.S. with potential to become a new cut flower commodity. Nothing is presently known about the mineral nutrition of bluebonnet in greenhouse conditions, either in the whole plant or its short-lived cut racemes, and its possible relationship with vase life longevity. At first appearance of floral buds, supplemental Ca treatments (0, 2.5, 5.0, and 10.0 mm Ca using CaCl2) were added to the nutrient solution over a 2-month growing period, to evaluate the influence of Ca on plant nutrient allocation patterns, nutrient uptake and utilization, and raceme physiology after cutting. Ca supplementation increased net Ca uptake per plant by 40%, 77%, and 95% over the control (2.5, 5.0, and 10.0 mm Ca, respectively; P < 0.05). The increased Ca uptake per plant increased Ca concentration in racemes (a weak Ca sink), which resulted in marginal increases in vase life duration (1 day). This positive influence on vase life duration was not significant due to limited number of raceme replicates. When plants were supplemented with 5 mm Ca, the net accumulation of Ca, P, K, and Mg in roots increased by 4 to 5 times over the control roots. These increases occurred in parallel to an increase in root dry matter production. Similar patterns were observed in the net accumulation of Ca, P, K, and Mg per plant. In our conditions, Ca supplementation (5 mm) enriched raceme Ca concentration as well as whole-plant consumption of Ca, P, K, and Mg in bluebonnet plants. These data will be useful in developing fertilization strategies for this new and promising greenhouse floral crop.

Crescimento aéreo e radicular da soja em solos compactados e inoculados com estirpes de Bradyrhizobium japonicum

Um experimento com soja, utilizando amostras de um Latossolo Vermelho-Escuro álico textura média foi realizado em casa de vegetação da Universidade Federal de Uberlândia (MG), de julho/96 a fevereiro/97, visando avaliar o comportamento de estirpes de Bradyrhizobium japonicum inoculadas e nativas do solo e efeitos de níveis de compactação subsuperficial na produção de matéria seca da parte aérea (PMSPA), de raízes no anel superior da coluna e na absorção e concentração de nitrogênio na parte aérea da soja. Os tratamentos dispostos em fatorial 2 x 3 x 4 corresponderam à brometização e não-brometização do solo, presença de três estirpes de Bradyrhizobium japonicum (nativa do solo, SEMIA 5079 e SEMIA 5080 inoculadas na semente) e de quatro níveis de compactação (densidades de: 1,15; 1,30; 1,45 e 1,60 kg dm-3), aplicados com prensa hidráulica no solo do anel central de uma coluna formada pela sobreposição de três anéis de PVC de 15 cm de diâmetro. Quarenta e sete dias após a emergência, as plantas foram cortadas, secas e pesadas, e as raízes do anel superior coletadas e quantificadas. A PMSPA foi crescente com a brometização do solo e inoculação com a estirpe SEMIA 5080, dentro das densidades de até 1,30 kg dm-3. Para valores maiores do que este, as estirpes estudadas não diferiram entre si. A compactação promoveu reduções lineares na produção de matéria seca da parte aérea no solo não-brometizado e parabólico, e maior produção na densidade de 1,35 kg dm-3 no solo brometizado. A concentração de nitrogênio na parte aérea foi significativamen-te menor com a inoculação da estirpe SEMIA 5079 no solo brometizado e não diferiu entre si no solo não brometizado. Maior produção de raízes na camada superficial ocorreu na ausência de brometização do solo e de inoculação com Bradyrhizobium japonicum. Com a brometização, a maior produção ocorreu com a inoculação da estirpe SEMIA 5079. A compactação produziu efeito linear crescente na produção de raízes no solo não brometizado e parabólico, com maior produção na densidade de 1,43 kg dm-3 no solo brometizado.

Wheat grown on volcanic ash with slow releasing nitrogen fertilizer and amended with sewage sludge compost

The volcanic ash of the Mount Pinatubo in Philippines is used in this study. The major drawbacks of this volcanic ash for growing agricultural crops are nitrogen (N) and iron (Fe) deficiencies with low organic matter contents. The objective of this study is to investigate the effect of sewage sludge compost on wheat through shoot and root development as well as dry matter production by pot culture. Either oxamide or polyolefinresin‐coated urea (PORCU) along with potash and phosphate fertilizers is applied to each pot containing volcanic ash. Application of sewage sludge compost in oxamide treatment yield a better plant height with an extended root length and high dry matter production compared to PORCU. However, statistical analysis of the data on plant height shows significant level (p<0.001, n=36), while those on root growth and dry matter production show no significant difference (p<0.335 and 0.564, n=36). Thus it is concluded that the coupling effect of oxamide and sewage sludge compost has a greater impact on plants, while growing on this ash.

Resposta de cultivares de feijoeiro ao enxofre

O experimento foi conduzido em casa de vegetação, no Departamento de Ciência do Solo da Universidade Federal de Lavras (UFLA), Lavras, MG, utilizando-se um Latossolo Vermelho-Amarelo, textura média, fase cerrado, proveniente do município de Itumirim, MG. Objetivou-se avaliar o efeito da aplicação de doses de S, no crescimento de três cultivares de feijoeiro (Phaseolus vulgaris L.), e a determinação dos níveis críticos do nutriente na parte aérea das cultivares. Utilizou-se um fatorial 4 x 3 (0, 30, 60 e 120 mg de S/kg de solo e as cultivares Carioca, Ouro e H-4), em delineamento inteiramente casualizado, com três repetições. As cultivares de feijoeiro apresentaram respostas significativas em produção de matéria seca da parte aérea (MSPA) quando se aplicou S, porém, com incrementos distintos em cada cultivar. À exceção da cultivar H-4, o fornecimento de S também estimulou a produção de matéria seca de raízes pelas plantas de feijoeiro, mas em menor intensidade que para a MSPA. Os níveis críticos internos de S na parte aérea, equivalentes a 90% da produção máxima de MSPA, variaram entre as cultivares. As relações N/S foram de 20,97, 20,81 e 18,68, enquanto a relação P/S foi de 2,24, 1,33 e 0,87 nas cultivares Carioca, Ouro e H-4, respectivamente. Os níveis críticos de S na MSPA das cultivares Carioca, Ouro e H-4 corresponderam, respectivamente, a 1,89, 2,21 e 2,16 g de S/kg. A eficiência de utilização de S, correspondente a 90% da produção máxima de MSPA, variou de acordo com as cultivares de feijoeiro, o que indica ser possível a seleção e melhoramento de material genético adaptado a condições distintas de disponibilidade desse nutriente no solo.

Effect of nitrogen form and phosphorus source on the growth, nutrient uptake and rhizosphere soil property of Camellia sinensis L.

The effects of nitrogen form and phosphorus source on the growth, nutrient uptake and rhizosphere soil property of tea (Camellia sinensis L.) were investigated in a pot experiment. The experiment was performed with a compartmental cropping device, which enables the collection of rhizosphere soil at defined distances from the root of tea plant. Nitrogen was supplied as nitrate or ammonium in combination with soluble phosphorus as Ca(H2PO4)2 or insoluble P as rock phosphate. The leaf dry matter production of tea was significantly greater in the treatments with NH4+ than NO3-, whereas dry matter production of root and stem was not significantly affected. Addition of phosphorus as either source did not influence the dry matter production. The concentrations of K in root, Mg and Ca in both the shoot and root supplied with NO3- were significantly higher than in NH4+ and influence of P sources was minor. On the contrary, Al and Mn concentrations were significantly larger in NH4--fed plants which could be attributed to remarkably increased availability of Al and Mn caused by acidification of the rhizosphere soil (the first 1-mm soil section from the root surface) with NH4–N nutrition. The concentration of N in shoot was also significantly higher in NH4- than in NO3-fed plants, indicating higher use efficiency of NH4–N. Whatever the phosphate source, rhizosphere pH declined in ammonium compared to in nitrate treatment. The pH decrease was much larger when no P or soluble P were applied and reached 0.85–1.30 units which extended to 3–5 mm away from the root surface. Exchangeable acidity, content of exchangeable Al and Mn were also considerably higher in the rhizosphere soils of NH4+ fed tea plants. Significant amounts of P dissolved from rock phosphate accumulated in rhizosphere of NH4+, not NO3-, suggesting that the dissolution of rock phosphate was induced by the proton excreted by tea root fed with ammonium. With soluble P addition, shoot and root P concentrations were greater in NH4+ than in NO3- treatment and it appeared that this difference could not be sufficiently explained by the available P content in soil which was only slightly higher in NH4+ treatment. With rock phosphate addition, the shoot and root P concentrations were hardly affected by nitrogen form, although the available P content was much higher and accumulated in the rhizosphere soil supplied with ammonium. The reason for this was discussed with regard to the inter-relationship of Al with P uptake.

Studies on the Effect of the Relative Humidity of the Atmosphere on the Growth andPhysiology of Rice Plants

SummaryThe seedlings of rice (Oryza sativa cv. Nipponbare) at a plant age of 3 leaves, were cultured for 10 days in a 12-h light/12-h dark cycle, and exposed to 60% (low) or 90% (high) relative humidity during the light and dark period in all combinations. Low humidity in light and high humidity in darkness, significantly increased the rate of leaf emergence, plant height, leaf area, leaf blade length, the number of roots, total root length and dry matter production as compared with low humidity in both light and dark periods. These results suggested that the effects of high humidity during the dark period on the growth and dry matter production is not nullified by low humidity during the light period. High humidity during the light period was significantly more effective than that during the dark period for the growth expressed by these parameters. The effects of high humidity during the light and dark periods on the plant height, leaf sheath length and width of leaf blade were additive, but those on the leaf-emergence rate, number of roots, total root length, leaf area, leaf blade length and dry matter production were not additive.

Differences Among Rice Cultivars in Root Exudation, Methane Oxidation, and Populations of Methanogenic and Methanotrophic Bacteria in Relation to Methane Emission

Greenhouse experiments were conducted under subtropical conditions to understand the mechanism of rice cultivar differences in methane (CH4) emission. Three rice cultivars were studied. Differences in CH4 emission rates among the three rice cultivars became evident in the middle and late growth stages. Rice root exudates per plant measured as total released C were significantly different among rice cultivars. The effect of root exudates on CH4 production in soil slurry differed accordingly. The amount of root exudates was not significantly different among rice cultivars when computed on a dry matter basis, indicating that it is positively correlated to root dry matter production. The root CH4-oxidizing activity differed among rice cultivars. IR65598 had a higher oxidative activity than IR72 and Chiyonishiki. Root air space was not significantly different among rice cultivars at the late growth stage, indicating that it is probably not a factor contributing to cultivar differences in CH4 emission. The population level of methanogenic bacteria differed significantly in soil grown to different rice cultivars, but not in roots, at booting stage and ripening stage. Methanotrophic bacteria population differed significantly in roots among rice cultivars at ripening. Rice cultivars with few unproductive tillers, small root system, high root oxidative activity, and high harvest index are ideal for mitigating CH4 emission in rice fields.

Soil Management and Supplemental Irrigation Effects on Potato: II. Root Growth

AbstractThis study was conducted to determine if supplemental irrigation and/or application of soil amendments rich in organic matter can improve root growth of potato (Solanum tuberosum L.). Root length density (RLD) and root dry matter production of potato were studied under two levels of supplemental irrigation (nonirrigated check vs. moderate irrigation) and two levels of soil amendments [none vs. amended with compost and manure from beef cattle (Bos taurus L.)] during 1993 and 1994. Amendments significantly increased RLD during both growing seasons and these increases occurred consistently throughout each growing season. Irrigation effects were not observed in 1993, while irrigation significantly increased RLD during 1994. Approximately 85% of the root length was concentrated in the upper 30‐cm layer of the soil. The supplemental irrigation and soil amendment treatments did not affect the proportional distribution of roots among the soil layers. Root‐to‐shoot ratio was not affected by irrigation or amendment during either growing season. The RLD and leaf area index (LAI) at all four sample dates during 1994 were significantly correlated with final tuber yields, indicating that growth patterns early in the season were important in establishing the productivity of the potato crop. Root length density tended to have a higher correlation with yields than did LAI (r = 0.58* to 0.80** vs. 0.51* to 0.68**).

Expression of high zinc efficiency of Aegilops tauschii and Triticum monococcum in synthetic hexaploid wheats

The effect of varied zinc (Zn) supply on shoot and root dry matter production, severity of Zn deficiency symptoms and Zn tissue concentrations was studied in two Triticum turgidum (BBAA) genotypes and three synthetic hexaploid wheat genotypes by growing plants in a Zn-deficient calcareous soil under greenhouse conditions with (+Zn=5 mg kg-1 soil) and without (−Zn) Zn supply. Two synthetic wheats (BBAADD) were derived from two different Aegilops tauschii (DD) accessions using same Triticum turgidum (BBAA), while one synthetic wheat (BBAAAA) was derived from Triticum turgidum (BBAA) and Triticum monococcum (AA). Visible symptoms of Zn deficiency, such as occurrence of necrotic patches on leaves and reduction in shoot elongation developed more rapidly and severely in tetraploid wheats than in synthetic hexaploid wheats. Correspondingly, decreases in shoot and root dry matter production due to Zn deficiency were higher in tetraploid wheats than in synthetic hexaploid wheats. Transfer of the DD genome from Aegilops tauschii or the AA genome from Triticum monococcum to tetraploid wheat greatly improved root and particularly shoot growth under Zn-deficient, but not under Zn-sufficient conditions. Better growth and lesser Zn deficiency symptoms in synthetic hexaploid wheats than in tetraploid wheats were not accompanied by increases in Zn concentration per unit dry weight, but related more to the total amount of Zn per shoot, especially in the case of synthetic wheats derived from Aegilops tauschii. This result indicates higher Zn uptake capacity of synthetic wheats. The results demonstrated that the genes for high Zn efficiency from Aegilops tauschii (DD) and Triticum monococcum (AA) are expressed in the synthetic hexaploid wheats. These wheat relatives can be used as valuable sources of genes for improvement of Zn efficiency in wheat.

Effect of elevated CO2 on carbon partitioning and exudate release from Plantago lanceolata seedlings

Plantago lanceolata L. seedlings were grown in sand microcosm units over a 43‐day experimental period under two CO2 regimes (800 or 400 µmol mol−1) to investigate the effect of elevated atmospheric CO2 concentration on carbon partitioning and exudate release. Total organic carbon (TOC) content of the collected exudate material was measured throughout the experimental period. After 42 days growth the seedlings were labelled with [14C]‐CO2 and the fate of the label within the plant and its release by the roots monitored. Elevated CO2 significantly (P ≤ 0.001) enhanced shoot, root and total dry matter production although the R:S ratio was unaltered, suggesting no alteration in gross carbon partitioning. The cumulative release of TOC (in mg C) over 0‐42 days was unaltered by CO2 treatment however, when expressed as a percentage of net assimilated C, ambient‐grown plants released a significantly (P≤ 0.001) higher percentage from their roots compared to elevated CO2‐grown plants (i.e. 8 vs 3%). The distribution of 14C‐label was markedly altered by CO2 treatment with significantly (P≤ 0.001) greater per cent label partitioned to the roots under elevated CO2. This indicates increased partitioning of recent assimilate below‐ground under elevated CO2 treatment although there was no significant difference in the percentage of 14C‐label released by the roots. Comparison of plant C budgets based on 14C‐pulse‐chase methodology and TOC measurements is discussed.

Dry matter production and uptake of zinc and phosphorus in two oilseed rape genotypes under differential rates of zinc and phosphorus supply

The effects of varied supply of zinc (Zn) (0, 0.1, 0.2, 1.0, and 10 mg Zn kg‐1 soil) and phosphorus (P) (low P: 50 mg P kg‐1 soil and high P: 150 mg P kg‐1 soil) on vegetative growth, plant tissue Zn and P concentration and their uptake were studied in six weeks old plants of two oilseed rape (Brassica napus) genotypes (92–13, a traditional genotype from China high in both erucic acid and glucosinolate, and Xinza‐2, a hybrid from China low in erucic acid and glucosinolate) grown in Laffer sand (low in Zn and P) under controlled environmental conditions. Two oilseed rape genotypes had a differential response to Zn application. Xinxa 2 responded significantly for shoot and root dry matter only up to 0.1 mg applied Zn kg‐1 soil, while 92–13 responded up to 0.2 mg Zn kg‐1 soil. Zinc at 10 mg kg‐1 soil slightly reduced shoot dry matter and drastically reduced root dry matter of both the genotypes. Shoot and root dry matter production at 0, 0.1, 0.2, and 1 mg Zn kg‐1 soil were significantly greater under high P supply compared with low P supply. High P supply did not accentuate Zn deficiency symptoms compared with low P supply even at nil Zn. Phosphorus concentration in plant parts was significantly higher at nil Zn compared with Zn application. An increase in P supply had a non‐significant effect on Zn concentration, but significantly increased the P concentration and P uptake in shoots. The results suggest that an increased supply of P at lower rates of Zn application was not detrimental for early vegetative growth and Zn uptake of two oilseed rape genotypes.

The influence of arsenic chemical form and concentration on Spartina patens and Spartina alterniflora growth and tissue arsenic concentration

Arsenic (As) uptake by two perennial coastal marsh grasses growing in hydroponic conditions was studied in relation to the chemical form and concentration of As added to nutrient solution. A 4×3×2 factorial experiment was conducted with treatments consisting of four As chemical forms [arsenite, As(III); arsenate, As(V); monomethyl arsonic acid, MMAA; and dimethyl arsinic acid, DMAA], three As concentrations (0.2, 0.8, and 2.0 mg As L-1) and two plant species (Spartina patens and Spartina alterniflora). Arsenic phytoavailability and phytotoxicity were primarily determined by the As chemical form present in the nutrient solution, though As concentration also influenced both As availability and toxicity. Application of As(V) increased root, shoot and total dry matter production; this positive plant growth response may be linked with P nutrition. Organic arsenicals and As(III) were the most phytotoxic species to both marsh grasses when plant growth was considered. Arsenic uptake and transport in plant were species-specific. Phytoavailability of As followed the trend DMAA ≪MMAA ≅ As(V) < As(III). Root and shoot As concentrations significantly increased with increasing As application rates to the rooting medium, regardless of the As chemical form. Upon absorption, inorganic arsenicals and MMAA were mainly accumulated in the root system, while DMAA was readily translocated to the shoot.

Amelioration of NaCl Stress by Triadimefon in Soybean Seedlings

NaCl stress decreased root growth, shoot length and dry matter production of Glycine max seedlings. It has also caused accumulation of proline and amino acids and decreased protein and nucleic acid contents of the seedlings. Addition of triadimefon to NaCl stressed seedlings partially restored the growth and increased the protein, amino acid, proline and nucleic acid contents of the seedlings. The root biomass production under combination of triadimefon and NaCl was even larger than control. Thus triadimefon can ameliorate the effect of NaCl stress in soybean.