Shoot Dry Weight Ratio Research Articles

Parâmetros morfológicos de mudas de Sesbania virgata (Caz.) Pers e de Anadenanthera peregrina (L.) cultivadas em substrato fertilizado com composto de lixo urbano

Objetivou-se avaliar o efeito do composto de lixo urbano nos parâmetros morfológicos de mudas de sesbânia e de angico. Os substratos de cultivo tiveram as seguintes proporções de composto e de amostras de subsolo de Neossolo Quartzarênico ou de Latossolo Vermelho-Amarelo (%): 0:100; 20:80; 40:60; 60:40 e 80:20, sem a utilização de fertilização mineral. As sementes de sesbânia foram inoculadas com a estirpe recomendada BR 5401. Os parâmetros morfológicos das mudas de sesbânia e angico, suas relações e índice de qualidade de Dickson (IQD) foram determinados aos 56 e 120 dias após a semeadura, respectivamente para cada espécie. Os efeitos dos substratos nos parâmetros morfológicos das mudas de sesbânia e angico variaram de acordo com as proporções do substrato. Para o angico, a adição do composto proporcionou aumento na altura da parte aérea, razão entre massa seca de parte aérea por massa seca de raiz e IQD. Para sesbânia, a adição do composto de lixo ao substrato proporcionou aumento na altura da parte aérea, diâmetro do coleto, massa seca de raiz, da parte aérea e total, razão entre massa seca da parte aérea por massa seca de raiz, IQD e número de nódulos. A obtenção de máxima produção de matéria seca total, diâmetro do coleto e IQD foi de 57:43, sendo, portanto, esta a proporção composta de lixo:solo recomendada para a produção de mudas de sesbânia.

Abstracts of Nippon Dojo-Hiryogaku Zasshi

Abstracts of Nippon Dojo-Hiryogaku Zasshi

Large variation in salinity tolerance in chickpea is explained by differences in sensitivity at the reproductive stage

Salinity is an ever-increasing problem in agriculture worldwide, especially in South Asia (India, Pakistan) and Australia. Improved genotypes that are well adapted to saline conditions are needed to enhance and sustain production in these areas. A screening of 263 accessions of chickpea, including 211 accessions from ICRISAT's mini-core collection (10% of the core collection and 1% of the entire collection), showed a 6-fold range of variation for seed yield under salinity (1.9 L of 80 mM NaCl per 7.5 kg Vertisol), with several genotypes yielding 20% more than a previously released salinity tolerant cultivar. The range of variation in yields under salinity was similar in both kabuli and desi chickpeas, indicating that breeding for salinity tolerance can be undertaken in both groups. A strong relationship ( r 2 = 0.50) was found between the seed yield under salinity and the seed yield under a non-saline control treatment, indicating that the seed yield under salinity was explained in part by a yield potential component and in part by salinity tolerance per se. Seed yields under salinity were therefore computed to separate the yield potential component from the residuals that accounted for salinity tolerance per se. Among the genotypes evaluated, desi genotypes had higher salinity tolerance than kabuli genotypes. The residuals were highly correlated to the ratio of seed yield under salinity to that of the control, indicating that both parameters can be used to assess salinity tolerance. A similar ratio was calculated for shoot dry weight at 50 days after sowing. However, no significant correlation was found between the shoot dry weight ratio and the yield ratio, indicating that differences in salinity tolerance among genotypes could not be inferred from measurements in the vegetative stage. The major trait related to salinity tolerance was the ability to maintain a large number of filled pods, whereas seed size was similar in tolerant and sensitive genotypes. Salinity tolerance was not related to the shoot Na + or K + concentrations.

Salinity and Growing Medium Regulate Growth, Morphology and Ion Uptake of Gaillardia aristata

Abstract A study was conducted to characterize the response of Gaillardia aristata Pursh to salinity (0.8, 2.0 or 4.0 dS/m) and growing media: 100% perlite (Perlite), 100% Sunshine Mix No. 4 (Mix), 1 to 1 (by vol) perlite and Sunshine Mix No. 4 (Perlite Mix), or 1 to 1 Sunshine Mix No. 4 and composted mulch (Mix Mulch). Type of medium did not influence shoot dry weight (DW). However, root to shoot DW ratio was highest for plants grown in Perlite. Shoot DW of plants irrigated with tap water (0.8 dS/m) was higher compared to those irrigated with saline solution at 2.0 or 4.0 dS/m, except for those grown in Mix. Salinity did not alter the root to shoot DW ratio. In general, elevated salinity led to relatively short plants. Plants were taller when grown in Perlite or Mix Mulch with fewer lateral shoots compared to plants grown in Mix and Perlite Mix. Flower bud abortion occurred in plants grown in Mix or Perlite Mix, while this phenomenon was not observed in plants grown in Perlite or Mix Mulch. Overall, plants performed better in Perlite and Mix Mulch than Mix and Perlite Mix.

Canola genotypes differ in potassium efficiency during vegetative growth

There is no knowledge about the differential capacity of canola genotypes to take up potassium (K) and produce dry matter under conditions of low soil K availability. Hence, 84 canola genotypes were screened for K efficiency in the glasshouse. Plants were grown in sealed pots containing K-responsive, sandy soil without or with K added. Twelve genotypes were selected for advanced screening in the glasshouse in a different K-responsive soil. Genotypes with a mean K efficiency ratio (the ratio of shoot dry weight at deficient and adequate K supply) greater than one standard error above or below the median genotype value were classified as K-efficient or K-inefficient, respectively. There were significant differences between genotypes in the K efficiency ratio in both screening experiments, indicating that genotypes responded differently to K availability. In the initial screening experiment, 19 genotypes were rated as K-efficient and nine genotypes rated as K-inefficient based on the K efficiency ratio. In the advanced screening experiment with 12 genotypes, three genotypes were rated as K-efficient and two as K-inefficient. Genotypes Wesbarker and Rainbow were K-efficient and Genkai K-inefficient in both experiments. Correlation of the K efficiency ratio with (i) shoot K content in the initial and advanced screening and (ii) shoot K concentration in the advanced screening, indicates that the observed differences in K efficiency were due to genotypic differences in both the uptake and the utilization of K. K-efficient genotypes have a potential to improve canola yields on soils with low K availability.

Effects of the Combined Application of Ethephon and Gibberellin on Growth of Rice (Oryza sativa L.) Seedlings

Improvement of early seedling growth, such as seedling emergence and vigor is one of the most important agronomic traits in direct seeding rice cultivation. The effects of two plant growth regulators (PGRs), gibberellic acid (GA3) and ethephon (ET), on seedling growth under flooded soil conditions at different temperatures and water depths were investigated. The PGRs were applied during the seed soaking process. A single treatment with GA3 or ET increased seedling growth. However, combined application of GA3 and ET was more effective than that of GA3 or ET alone in many cases at both growing temperatures (15 and 20ºC). The growth of different organs in the rice seedlings, such as the coleoptiles, first leaves, and second leaves was also increased by PGR treatment. The nitrogen concentration of the shoot and the ratio of shoot dry weight to shoot length did not differ significantly among the treatments. The results of our study show that rice seedling growth in direct seeding cultivation may be improved by treatment with GA3 and ET in combination.

Model-assisted physiological analysis of Phyllo, a rice architectural mutant.

Studies of phenotype of knockout mutants can provide new insights into physiological, phenological and architectural feedbacks in the plant system. Phyllo, a mutant of Nippon Bare rice (Oryza sativa L.) producing small leaves in rapid succession, was isolated during multiplication of a T-DNA insertion library. Phyllo phenotype was compared with the wild type (WT) during vegetative development in hydroponics culture using a wide range of physiological and biometric measurements. These were integrated with the help of the functional-structural model EcoMeristem, explicitly designed to study interactions between morphogenesis and carbon assimilation. Although the phenotype of the mutant was caused by a single recessive gene, it differed in many ways from the WT, suggesting a pleiotropic effect of this mutation. Phyllochron was 25 (1-4 leaf stage) to 38% (>>4 leaf stage) shorter but showed normal transition from juvenile to adult phase after leaf 4. Leaf size also increased steadily with leaf position as in WT. The mutant had reduced leaf blade length : width and blade : sheath length ratios, particularly during the transition from heterotrophic to autotrophic growth. During the same period, root : shoot dry weight ratio was significantly diminished. Specific leaf area (SLA) was strongly increased in the mutant but showed normal descending patterns with leaf position. Probably related to high SLA, the mutant had much lower light-saturated leaf photosynthetic rates and lower radiation use efficiency (RUE) than the WT. Leaf extension rates were strongly reduced in absolute terms but were high in relative terms (normalised by final leaf length). The application of the EcoMeristem model to these data indicated that the mutant was severely deficient in assimilate, resulting from low RUE and high organ initiation rate causing high assimilate demand. This was particularly pronounced during the heterotrophic-autotrophic transition, probably causing shorter leaf blades relative to sheaths, as well as a temporary reduction of assimilate partitioning to roots. The model accurately simulated the mutant's high leaf mortality and absence of tillering. The simulated assimilate shortage was supported by observed reductions in starch storage in sheaths. Soluble sugar concentrations differed between mutant and WT in roots but not in shoots. Specifically, the hexose : sucrose ratio was 50% lower in the roots of the mutant, possibly indicating low invertase activity. Furthermore, two OsCIN genes coding for cell wall invertases were not expressed in roots, and others were expressed weakly. This was interpreted as natural silencing via sugar signalling. In summary, the authors attributed the majority of observed allometric and metabolic modifications in the mutant to an extreme assimilate shortage caused by hastened shoot organogenesis and inefficient leaf morphology.

VARIATION IN PLANT AND SOIL WATER RELATIONS AMONG IRRIGATED BLUEBERRY CULTIVARS PLANTED AT TWO DISTINCT IN-ROW SPACINGS

A study was conducted to determine the effect of in-row spacing on plant and soil water relations in 'Duke', 'Bluecrop', and 'Elliott' highbush blueberry (Vaccinium corymbosum L.) and to identify possible mechanisms that may enhance the ability of these cultivars to tolerate short-term soil water deficits. Changes in soil water content, stem water potential, and leaf stomatal conductance were measured 4 years after planting on well-irrigated plants of each cultivar spaced 0.5 or 1.2 m within rows on raised beds (~0.3 m high) and 3.0 m between rows. Irrigation (711 mm) was applied equally to all treatments by overhead sprinklers during the dry summer months from mid-May to early-September. Close spacing significantly reduced individual shoot dry weight, but also significantly increased crop light interception and water uptake from 0-0.6 m soil depth compared to plants spaced further apart. Spacing had little effect, however, on plant water relations. Independent of cultivar and spacing, stomatal conductance decreased rapidly as stem water potential approached -0.6 to -0.8 MPa. Among cultivars, 'Bluecrop' had the lowest root mass and root:shoot dry weight ratio at either spacing, while 'Elliott' had the highest. 'Duke', however, produced the deepest root system, extracting a significant amount of water below 0.6 m when plants were closely spaced. 'Duke' also maintained, on average, higher stem water potentials and greater stomatal conductance than the other cultivars as soil water was depleted.

Bigtooth Maples Exposed to Asynchronous Cyclic Irrigation Show Provenance Differences in Drought Adaptation Mechanisms

Ecological traits such as an extensive range of natural distribution and tolerance to varying soil conditions, suggest that bigtooth maples (Acer grandidentatum Nutt.) could be popular landscape trees. But information on the tolerance of bigtooth maples to environmental stresses, such as drought, is virtually nonexistent. We studied physiological, growth and developmental traits of bigtooth maple plants from 15 trees native to Arizona, New Mexico, Texas, and Utah. Plants were grown in pots in a greenhouse and maintained as well-irrigated controls or exposed to drought and irrigated in cycles based on evapotranspiration. The ratio of variable to maximal fluorescence (Fv/Fm) was not different between drought-stressed and control plants, but the low Fv/Fm in plants designated as LM2 from the Lost Maples State Natural Area in Vanderpool, Tex., suggests these plants were relatively inefficient in capturing energy at PSII. Plants from another tree (LM5) originating from Lost Maples State Natural Area maintained similar predawn water potentials between drought-stressed and control plants after five cycles of drought. Plants from Dripping Springs State Park in Las Cruces, N.M., and those from LM2 had a strong, significant linear relationship between transpiration and stomatal conductance. Drought-stressed plants from Dripping Springs State Park, two plant sources from the Guadalupe Mountains in Salt Flat, Tex., designated as GM3 and GM4, and plants from trees designated as LM1 and LM2, had high relative growth rates and net assimilation rates. Drought-stressed plants from three of the four Guadalupe Mountain sources (GM1, GM3, GM4) had among the longest and thickest stems. Drought reduced shoot and root dry weight (DW). Although bigtooth maples showed several provenance differences in drought adaptation mechanisms, the lack of an irrigation effect on biomass allocation parameters such as root to shoot DW ratio and leaf area ratio implies that altered biomass allocation patterns may not be a common drought adaptation mechanism in bigtooth maples. Plants from selected provenances from the Guadalupe Mountains and Lost Maples State Natural Area in Texas, and to a lesser extent, provenances from Dripping Springs State Park in New Mexico might hold promise for selecting bigtooth maples for arid environments.

Tolerance to Zinc Deficiency in Rice Correlates with Zinc Uptake and Translocation

To study variation in zinc efficiency (ZE) among current Chinese rice genotypes, a pot experiment was conducted with 15 aerobic and 8 lowland rice genotypes. Aerobic rice is currently bred by crossing lowland with upland rice genotypes, for growth in an aerobic cultivation system, which is saving water and producing high yields. A Zn deficient clay soil was used in our screening. Zn deficiency resulted in a marked decrease in shoot dry matter production of most genotypes after 28 days of growth. Genotypes were ranked according to their tolerance to Zn deficiency based on ZE, expressed as the ratio of shoot dry weight at Zn deficiency over that at adequate Zn supply. Substantial genotypic variation in ZE (50–98%) was found among both lowland and aerobic genotypes. ZE correlated significantly (P < 0.05) with Zn uptake (R2 = 0.34), Zn translocation from root to shoot (R2 = 0.19) and shoot Zn concentration (R2 = 0.27). The correlation with seed Zn content was insignificant. In stepwise multiple regression analyses, variation in Zn uptake and Zn translocation explained 53% of variation in ZE. Variation in Zn uptake could be explained only for 32% by root surface area. These results indicate that Zn uptake may be an important determinant of ZE and that mechanisms other than root surface area are of major importance in determining Zn uptake by rice.

Influence of arbuscular mycorrhizal fungi and kinetin on the response of mungbean plants to irrigation with seawater

Increasing use of saline water in irrigation can markedly change the physical and chemical properties of soil. An experiment was carried out to investigate the interaction between the mycorrhizal fungus Glomus clarum, isolated from a saline soil, and kinetin on the growth and physiology of mungbean plants irrigated with different dilutions of seawater (0, 10, 20, and 30%). The growth, chlorophyll concentration and sugar content of mycorrhizal plants was greater than that of non-mycorrhizal plants under all conditions (with or without seawater). The dry weight of both mycorrhizal and non-mycorrhizal mungbean plants irrigated with 10% seawater was significantly increased by treatment with kinetin. The mycorrhizal symbiosis increased root:shoot dry weight ratio, concentrations of N, P, K, Ca and Mg, plant height, protein content, nitrogen or phosphorus-use efficiencies, and root nitrogenase, acid or alkaline phosphatase activities of seawater-irrigated mungbean plants, with little or no effect of kinetin. Kinetin treatment generally decreased chlorophyll concentration and sugar content in mycorrhizal plants as well as Na/N, Na/P Na/K, Na/Ca and Na/Mg ratios. Root colonization by G. clarum was increased by irrigation with seawater, and kinetin had no consistent effect on fungal development in roots. This study provides evidence that arbuscular mycorrhiza can be much more effective than kinetin applications in protecting mungbean plants against the detrimental effects of salt water.

Water Relations, Growth, and Carbon Isotope Discrimination of Drought-stressed Bigtooth Maples Indigenous to New Mexico, Texas, and Utah

Although valued for its fall foliage color, bigtooth maple (Acer grandidentatum Nutt.) is not widely used in managed landscapes. Furthermore, information on the tolerance of bigtooth maples to drought is scant. We studied water relations, plant development, and carbon isotope composition of bigtooth maples indigenous to New Mexico, Texas, and Utah. Plants were field grown in New Mexico using a pot-in-pot nursery production system. Plants were maintained as well-irrigated controls or irrigated after the weight of pots decreased by 35% due to evapotranspiration. Drought treatment lasted 71 days. Among the drought-stressed plants, plants native to Logan Canyon in Utah (designated UW2), had the greatest root: shoot dry weight ratio (3.0), while plants with the lowest root: shoot dry weight ratio (0.9) were half siblings from a tree native to the Lost Maples State Park in Texas (designated LMP5). Among the five sources we tested, LMP5 had the greatest (1242 cm2) leaf area, while UW2 plants had the smallest (216 cm2). Regardless of the treatment, plants from LMP5 had the highest shoot dry weight (25.7 g). Plants showed no differences neither among sources nor between treatments in relative water content, specific leaf weight, xylem diameter, root dry weight, plant dry weight, relative growth rate, and carbon isotope discrimination, which averaged - 26.53%. The lack of differences in these parameters might be due to selection of these sources from provenances we deemed to be the most drought tolerant. Our selection was based on the results of a previous greenhouse study of 15 bigtooth maple sources. We conclude that these sources, and in particular, plants from LMP5 in Texas, might hold promise for use in areas prone to drought.

Effects of elevated CO2 concentration on growth, water use, yield and grain quality of wheat under two soil water levels

Wheat (Triticum aestivum L.) is one of the most important food sources in the world. The potential impacts of elevated CO2 on wheat yield and grain quality will have profound influences on the supply and nutritional value of wheat products as well as on many industrial sectors. A growth-chamber experiment was designed to estimate how soil moisture influences the potential effects of elevated CO2 concentration ([CO2]) on wheat growth, water use and grain yield. Spring wheat (T. aestivum cv. Ganmai 8139) was grown in pots placed in controlled growth chambers and was subjected to two [CO2] (approximately 350 and 700l/l, respectively) and two soil water levels (80 and 40% of field water capacity (FWC), respectively). High [CO2] increased plant shoot dry weight by 89% under 80% FWC and by 53% under 40% FWC. Grain yield of wheat was markedly increased under elevated [CO2] with greater grain number and harvest index. The ratio of plant shoot dry weight to height was increased by 75% under high [CO2] at high soil moisture, and by 54% at low moisture. Water use efficiency of shoot (WUEs) and grain yield (WUEg) were increased under high [CO2] because the magnitude of the increase in shoot dry weight and grain yield was greater than that of the cumulative consumption of water under high [CO2] conditions. When wheat plants were under high [CO2] conditions and maintained at high moisture, the WUEs and WUEg were increased by 62 and 128%, respectively. Elevated [CO2] resulted in lower concentrations of mineral nutrients (N, P, K and Zn), lysine and crude protein in mature grains. This was probably caused by a dilution effect induced by great increment of carbohydrate in grains. The total quantity of mineral nutrients, lysine and crude protein accumulated in grains per hectare were still increased under high [CO2] due to increase in grain yield. Our results indicate that high [CO 2] is beneficial to plant growth, yield and WUE, while grain quality was lowered under high [CO2] conditions as reflected by the increased crude starch content, and corresponding decreases in mineral nutrients, lysine and crude protein concentrations. The analysis of yield components suggested that the yield increase was mainly attributable to an increase in the number of grains. However, the effects of CO 2 enrichment on plants depend on the availability of soil moisture, and plants may benefit more from CO 2 enrichment when sufficient water is supplied. © 2004 Elsevier B.V. All rights reserved.

Stimulation of nodulation and plant growth of chickpea ( Cicer arietinum L . ) by Pseudomonas spp. antagonistic to fungal pathogens

Two strains of Pseudomonas MRS23 and CRP55b showed antagonistic activity towards the pathogenic fungi Aspergillus sp., Fusarium oxysporum f. sp. ciceri, Pythium aphanidermatum and Rhizoctonia solani under culture conditions. Larger growth inhibition zones were obtained on nutrient agar (NA) and King's B media in comparison to potato dextrose agar and pigment production media. Both the strains produced siderophore in agar plates as well as in liquid cultures. Fungal inhibition zones were reduced in size and abolished in iron-supplemented NA medium by Pseudomonas strains MRS23 and CRP55b, respectively, indicating that some other metabolites along with siderophores are involved in growth inhibition of fungi by strain MRS23, whereas CRP55b produced only siderophores. Only Pseudomonas strain MRS23 was found to produce hydrocyanic acid (HCN). Seed bacterization with Pseudomonas strains of two chickpea (Cicer arietinum L.) cultivars, H8618 and C235, showed root-stunting effects at 5 days, whereas this inhibitory effect was overcome at 10 days of seedling growth in cv. H8618. Coinoculation of chickpea with Pseudomonas strains MRS23 and CRP55b, and Mesorhizobium sp. Cicer strain Ca181 resulted in the formation of 68.2–115.4% more nodules at 80 and 100 days after planting as compared to single inoculation with the Mesorhizobium strain under sterile conditions. The shoot dry weight ratios of coinoculated treatments at different stages of plant growth varied from 1.18 to 1.35 times that of Mesorhizobium-inoculated and 3.25 to 4.06 times those in uninoculated controls. The plant N contents were also increased significantly on coinoculation. Coinoculation effects of HCN-producing strain MRS23 were significantly lower than those of non-HCN-producing strain CRP55b in terms of shoot dry weight and shoot N. The results demonstrated the potential benefits of using rhizosphere bacteria as coinocula in nodule promotion and plant growth in chickpea.

Drought Responses among Seven Southwestern Landscape Tree Taxa

Identification of tree taxa that can thrive on reduced moisture regimes mandated by xeriscape programs of the southwest United States could be facilitated if responses to drought of those taxa are determined. Leaf water relations, plant development, and cuticular wax content of seven taxa maintained as well-irrigated controls or exposed to drought and irrigated based on evapotranspiration were studied. Leaf water potential of drought-stressed Fraxinus velutina Torr. (Arizona ash), Koelreuteria paniculata Laxm. (golden rain tree), Quercus macrocarpa Michx. (bur oak), and Quercus muehlenbergii Engelm. (chinkapin oak) were lower at predawn than the controls. Drought-stressed plants of F. velutina, K. paniculata, and Quercus lobata Née (California white oak) had more negative midday water potential than the control plants. Drought reduced stomatal conductance to as little as 17%, 23%, and 45% of controls in F. velutina, K. paniculata, and Q. macrocarpa, respectively. Drought-stressed plants of F. velutina, K. paniculata, Q. macrocarpa, and Q. muehlenbergii had reduced transpiration rates. Fraxinus velutina had both the highest net assimilation rate (NAR) and relative growth rate (RGR) regardless of irrigation treatment. Mean specific leaf weight (dry weight (DW) of a 1-cm2 leaf disc divided by the weight), trichome density, stomatal density, leaf thickness, and cuticular wax content varied among species but not between irrigation treatments. Leaves of Q. buckleyi Buckl. (Texas red oak) had one of the highest stomatal densities, and also had leaves which were among the waxiest, most dense, and thickest. Abaxial leaf surfaces of F. velutina were the most pubescent. Across species, drought led to lower ratios of leaf surface area to root DW, and leaf DW to root DW. Quercus buckleyi plants subjected to drought had the highest root to shoot DW ratio (3.1). The low relative growth rate of Q. buckleyi might limit widespread landscape use. However, Q. buckleyi may merit increased use in landscapes on a reduced moisture budget because of foliar traits, carbon allocation patterns, and the relative lack of impact of drought on plant tissue water relations.

TOLERANCE OF 65 DURUM WHEAT GENOTYPES TO ZINC DEFICIENCY IN A CALCAREOUS SOIL

Sixty-five durum wheat (Triticum turgidum ssp. durum) genotypes were grown in a zinc (Zn)-deficient calcareous soil in a greenhouse for 32 days with (+Zn=5 mg Zn kg−1 soil) and without (−Zn) Zn supply to study genotypic variation in tolerance to Zn deficiency. Genotypes were ranked for their tolerance to Zn deficiency based on the relative shoot growth (Zn efficiency ratio) defined as the ratio of shoot dry weight under Zn deficiency to the shoot dry weight under adequate Zn supply. Zinc deficiency resulted in marked decreases in shoot dry matter production of the genotypes following 32 days of growth. Shoot dry weight of most genotypes was similar under adequate Zn supply, but differed greatly under Zn deficiency. Consequently, the Zn efficiency ratio showed a large variability and ranged between 20% to 51%. Generally, the genotypes showing lower tolerance to Zn deficiency had lower absolute shoot dry weight under Zn deficiency than the genotypes having greater tolerance to Zn deficiency. Differences in tolerance to Zn deficiency were related very significantly to the total amount (content) of Zn per shoot of the genotypes, but poorly to the concentration of Zn in shoot. As the shoot Zn concentration did not vary much between the genotypes under Zn deficiency, the higher amount of Zn per shoot of the Zn-efficient genotypes was a reflection of their greater shoot dry weight. Seed Zn concentration of the genotypes was quite similar and ranged from 18 to 25 mg kg−1 DW for almost all genotypes. Therefore, the genotypic variation in tolerance to Zn deficiency was most likely inherent and not related to the seed Zn content. The results of the present study show existence of a large variation in tolerance to Zn deficiency in durum wheat, and suggest that the absolute shoot growth like the relative shoot growth (Zn efficiency ratio) can be used as a reliable plant parameter for screening the durum wheat genotypes for their tolerance to Zn deficiency, provided that genotypes have a similar growth rate under adequate Zn supply.

Stability of Provenance Differences during Development of Hard Maple Seedlings Irrigated at Two Frequencies

Traits associated with drought resistance vary with provenance of hard maples (Acer sp.), but the stability of differences ex situ and over time is unknown. We compared growth, dry-matter partitioning, leaf anatomy, and water relations of seedlings from central Iowa, eastern Iowa, and the northeastern United States over 2 years. Some seedlings from each of the three provenances were used as well-irrigated controls. The remaining seedlings were drought-stressed and irrigated based on evapotranspiration. Across irrigation treatments, plants from Iowa had shorter stems and higher specific weight of lamina, root: shoot dry-weight ratios, and root: lamina dry-weight ratios than did plants from the northeastern United States when treatments began. Biomass partitioning did not differ based on provenance after irrigation treatment for 2 years, but leaves from central Iowa had a higher specific weight, and their abaxial surfaces had more stomates and trichomes, than did leaves from the Northeast. Drought stress reduced conductance only in plants from central Iowa. Across provenances, drought stress reduced stomatal frequency, surface area of laminae, and dry weights of laminae and roots, and increased root: shoot dry-weight ratio. Leaf water potential of plants subjected to drought was lower at predawn and higher at midday than that of control plants. Drought did not cause osmotic adjustment in leaves. We conclude that the stability of foliar differences among provenances of hard maples validates using these traits as criteria for selecting ecotypes for use in managed landscapes prone to drought.

Relationship between Cold Tolerance during Seed Germination and Vegetative Growth in Tomato: Germplasm Evaluation

Cold tolerance (CT) of 31 tomato accessions (cultivars, breeding lines, and plant introductions) representing six Lycopersicon L. sp. was evaluated during seed germination and vegetative growth. Seed germination was evaluated under temperature regimes of 11 ± 0.5 °C (cold stress) and 20 ± 0.5 °C (control) in petri plates containing 0.8% agar medium and maintained in darkness. Cold tolerance during seed germination was defined as the inverse of the ratio of germination time under cold stress to germination time under control conditions and referred to as germination tolerance index (TIG). Across accessions, TIG ranged from 0.15 to 0.48 indicating the presence of genotypic variation for CT during germination. Vegetative growth was evaluated in growth chambers with 12 h days/12 h nights of 12/5 °C (cold stress) and 25/18 °C (control) with a 12 h photoperiod of 350 mmol.m-2.s-1 (photosynthetic photon flux). Cold tolerance during vegetative growth was defined as the ratio of shoot dry weight (DW) under cold stress (DWS) to shoot DW under control (DWC) conditions and referred to as vegetative growth tolerance index (TIVG). Across accessions, TIVG ranged from 0.12 to 0.39 indicating the presence of genotypic variation for CT during vegetative growth. Cold tolerance during vegetative growth was independent of plant vigor, as judged by the absence of a significant correlation (r = 0.14, P &gt; 0.05) between TIVG and DWC. Furthermore, CT during vegetative growth was independent of CT during seed germination, as judged by the absence of a significant rank correlation (rR = 0.14, P &gt; 0.05) between TIVG and TIG. A few accessions, however, were identified with CT during both seed germination and vegetative growth. Results indicate that for CT breeding in tomato, each stage of plant development may have to be evaluated and selected for separately.

Response of differentiated and degenerated spikelets to top-dressing, shading and day/night temperature treatments in rice cultivars with large panicles

The presence of large panicles enables to reach a sufficient number of surviving spikelets per unit area for further increase of rice yield. However, the response of differentiated and degenerated spikelets to environmental factors in terms of number in cultivars with large panicles has not been elucidated. By applying top-dressing at different rates and frequencies, shading, and day/night temperature treatments in pot experiments, we observed the response of the main stem in two cultivars with large panicles: Yangdao 4 (Chinese indica) and Akenohoshi (Japanese japonica-indica hybrid). The results showed that top-dressing increased the number of differentiated spikelets per panicle and decreased the percentage of degenerated spikelets. Consequently, the number of surviving spikelets per panicle increased. Shading increased the percentage of degenerated spikelets, resulting in the decrease of the number of surviving spikelets per panicle. Higher day/night temperature treatments led to a higher percentage of degenerated spikelets. The treatments affected mainly the spikelets on the secondary branches, while the number of spikelets on the primary branches did not change appreciably, irrespective of the presence of differentiated, degenerated, and surviving spikelets. The influence on the number of surviving spikelets per panicle depended on the number of differentiated spikelets. Shading effect on the percentage of degenerated spikelets also depended on the number of differentiated spikelets per panicle. The decrease of the percentage of degenerated spikelets was associated with the increase of the shoot dry weight (SDW) at heading and the ratio of SDW-differentiated spikelets. The SDW and N absorption at heading affected more significantly the number of surviving spikelets compared to the ratio of surviving spikelets-SDW and surviving spikelets-N, respectively. The above results were similar in Akenohoshi and Yangdao 4. In Akenohoshi, the percentage of degenerated spikelets responded much more conspicuously to the change of SDW or the ratio of SDW -differentiated spikelets than that in Yangdao 4. So did the number of surviving spikelets to SDW and N absorption at heading. Akenohoshi showed a higher ratio of surviving spikelets-N than Yangdao 4. These differences may account for the fact that Akenohoshi showed a larger number of surviving spikelets per panicle than Yangdao 4, even at the same levels of SDW and N absorption.

Growth of field horsetail (Equisetum arvense) under low light and low nitrogen conditions

Field horsetail was grown from rhizome segments for 28 and 52 d under 35, 60, 120, 170, and 320 μmol m–2s–1photosynthetic photon flux (PPF) and four continuous nitrogen (N) supply rates corresponding to a total of 1 to 6 kg N ha–128 d after planting (DAP) and 6 to 41 kg N ha–152 DAP. There was no response to the supply of N in the first growth period, probably due to the mobilization of nitrogen available in the planted rhizomes, and only dry weight (DW) of new belowground production, mostly roots, responded to increased light. Rhizomes were produced during the latter part of the 52-d period. Requirements for light and N during the 52-d period were low, because total new tissue production was only reduced at the lowest levels of light (35 μmol m–2s–1PPF) and the two lowest N supply rates (6 and 18 kg N ha–1). The ratio of shoot DW to belowground organ DW increased only as the N supply increased. Shoot height response to an increased N supply was also small. Field horsetail can therefore be considered tolerant of low levels of N but will be overtopped by fast-growing species when competing for increased supplies of N. Both an increase in N supply and a reduction in light increased the reduction of DW of the planted rhizomes, whereas tuber production was favored by low N supply and high light intensities. Field horsetail can tolerate low levels of N but is not likely to be competitive in a dense crop stand.