Greater Root Dry Weight Research Articles

Rice near-isogenic-lines (NILs) contrasting for grain yield under lowland drought stress

The development of near-isogenic-lines (NILs) is a very important tool for both genetic and physiological dissection of drought resistance in rice. Two pairs of NILs differing for grain yield under drought stress were isolated and characterized for yield, yield related traits, and several physiological traits in a range of contrasting environments. In replicated field trials both NIL pairs differed significantly for grain yield under drought stress but showed similar yield potential, phenology, and yield component traits under non-stress conditions. A polymorphism analysis study with 491 SSRs revealed that both NIL pairs are at least 96% genetically similar. These NILs show that small genetic differences can cause large difference in grain yield under drought stress in rice. In both pairs the drought-tolerant NILs showed a significantly higher assimilation rate at later stages both under stress and non-stress conditions. They also had a higher transpiration rate under non-stress condition. The most tolerant NIL (IR77298-14-1-2-B-10) had significantly higher transpiration rate and stomatal conductance in severe stress conditions. In one pair the tolerant NIL had constitutively deeper roots than the susceptible NIL. In the second pair, which had higher mean root length than the first pair, the tolerant NIL had more roots, greater root thickness, and greater root dry weight than the susceptible NIL. Deeper root length may allow tolerant NILs to extract more water at deeper soil layers. It is concluded that enhanced rooting depth is an important strategy for dehydration avoidance and rice adaptation to drought stress, but root architecture might not be the only mechanism causing the significant yield increase we observed in lowland drought stress environments. To further dissect the drought avoidance mechanisms in rice, analysis of root hydraulic properties may be necessary.

Impact of mycorrhizal colonisation on grapevine establishment in <i>Cylindrocarpon</i> infested soil

The effects of arbuscular mycorrhizae (AM) Glomus mosseae and Acaulospora laevis on growth of six grape rootstock varieties and their infection by Cylindrocarpon species were investigated in a greenhouse experiment that challenged the mycorrhizal plants with a mixed inoculum of Cylindrocarpon spp Both species of AM had beneficial effects (P005) but greater root dry weights in Auckland (214; P005) G mosseae clearly has potential for improving health and growth of young grapevine plants

Interactions between N, P and C mobilisations during spring growth of a semi-evergreen shrub ( Ligustrum ovalifolium L.) grown in containers with different fertilisation schedules

Container-grown Ligustrum ovalifolium L. plants were used to determine the influence of nutrient availability on the mobilisation of carbon (C), nitrogen (N) and phosphorus (P) during spring growth. During the spring of the second growing season, plants either received no fertiliser, or were fertilised early (starting 17 days after bud break) or late (starting 3 months after bud break). Nutrient composition of different plant tissues was determined at several times during the second growing season from bud break to the end of elongation. Time of fertilisation did not influence aerial dry weight until flowering was completed. Plants that received no fertiliser or were fertilised late had greater root dry weight than plants that received fertiliser early. Fertilised plants had a second flush of growth after flowering completed. Nitrogen and phosphorus mobilisation occurred from bud break to the end of elongation (3 months). Nutrient mobilisation was effective in each perennial organ: root, trunk, ligneous stems and old leaves. However, the role of old leaves as storage organ was minor compared to evergreen tree leaves. Carbon mobilisation only occurred on the 1st month following bud break, before elongation. C-starch accumulation was observed in unfertilised plants even when the C-starch quantities in early fertilised plants were very low at the end of elongation, mainly in roots. In spite of fertilisation supplies, N and P quantities did not increase after elongation in the early fertilised plants, probably in relation to C insufficiency in roots to sustain N and P absorption and assimilation. By contrast, in late fertilised plants, high C quantities in roots were mobilised for N and P uptake and assimilation, which allowed both second growth flush and storage of N and P in perennial organs. The mobilisation of nutrients before and during elongation revealed the nutritional autonomy of shrubs, which could allow fertiliser use efficiency to be increased and environmental impacts to be minimised by delaying spring fertilisation. Nevertheless, the shrub ability to valorise fertilisation supplies for sustaining growth or nutrient storage restoration required sufficient C-starch quantities in roots. The starch accumulated in roots before late nutrient supply can be used for these objectives.

Role of the rooting system in salt tolerance potential of different guar accessions

To examine the role of the rooting system in salt tolerance of 15 guar (Cyamopsis tetragonoloba L.) accessions collected from arid and semi-arid regions of Pakistan, a pot-culture experiment was conducted under natural conditions in a net house. The experiment comprised three salinity treatments, i.e., 3, 9 and 15 dS m -1 , with three replications. The results showed that whole plant dry weight, root length, root dry weight and number of nodules decreased due to salinity in all the accessions; however, different guar accessions showed variation in root length, dry weight and number of nodules under normal and stressed conditions. The root morphology revealed that accessions with a longer root, greater root dry weight and higher number of nodules had higher seed yield. A positive relationship was found between the rooting system and seed yield under salt stress. It is concluded that accessions with better rooting systems produced higher seed yield and were more salt-tolerant than others.

Indirect Selection for Root Development of White Clover and Implications for Drought Tolerance

AbstractImproving white clover drought tolerance by selecting for more developed roots is controversial, labour‐consuming and complicated by the adventitious root system. This study aimed at assessing: (i) the value of thicker stolons as an indirect selection criterion for increasing root development, (ii) the relationship between root development and drought tolerance, and (iii) the consistency of population response for root and shoot traits between swards derived from seedlings or stolon cuttings. Thick‐ and thin‐stolon populations obtained by one cycle of divergent phenotypic selection within one ladino landrace, and one ladino natural population, were evaluated in metal containers (0.55 m × 0.12 m × 0.75 m deep) in a 1‐year experiment including vegetative material (seedling or stolon cutting) and drought stress (absent or present) as additional factors. Aerial dry weight (DW) was also assessed across two summer harvests under irrigated and rainfed field conditions for the thick‐stolon selection, two breeding populations selected from the same landrace regardless of stolon thickness, and the drought‐tolerant ladino ‘Brown Loam Synthetic no. 2’. The thick‐stolon selection had greater root DW (+21 %) than the thin‐stolon selection besides thicker stolons (+23 %). The natural population combined thinnest stolons with lowest root DW. Differences between populations were consistent across vegetative material. Primary and adventitious root systems did not differ for root DW in deeper soil horizons (>23 cm), above‐ground biomass and its reduction due to drought stress. Root DW increased under stress, particularly in deeper horizons. Aerial DW variation among populations evened up or narrowed much under stress, with no cross‐over interaction leading to an advantage of thick‐stolon material or ‘Brown‐Loam Synthetic no. 2’.

Over-expression of cytosolic glutamine synthetase increases photosynthesis and growth at low nitrogen concentrations.

Nitrogen, which is a major limiting nutrient for plant growth, is assimilated as ammonium by the concerted action of glutamine synthetase (GS) and glutamate synthase (GOGAT). GS catalyses the critical incorporation of inorganic ammonium into the amino acid glutamine. Two types of GS isozymes, located in the cytosol (GS1) and in the chloroplast (GS2) have been identified in plants. Tobacco (Nicotiana tabacum) transformants, over-expressing GS1 driven by the constitutive CaMV 35S promoter were analysed. GS in leaves of GS-5 and GS-8 plants was up-regulated, at the level of RNA and proteins. These transgenic plants had six times higher leaf GS activity than controls. Under optimum nitrogen fertilization conditions there was no effect of GS over-expression on photosynthesis or growth. However, under nitrogen starvation the GS transgenics had c. 70% higher shoot and c. 100% greater root dry weight as well as 50% more leaf area than low nitrogen controls. This was achieved by the maintenance of photosynthesis at rates indistinguishable from plants under high nitrogen, while photosynthesis in control plants was inhibited by 40-50% by nitrogen deprivation. It was demonstrated that manipulation of GS activity has the potential to maintain crop photosynthetic productivity while reducing nitrogen fertilization and the concomitant pollution.

Banded Phosphorus Effects on Alfalfa Seedling Growth and Productivity After Temporary Waterlogging

Phosphorus applied in a band below alfalfa (Medicago sativa L.) seed can increase seedling growth. A field study was conducted to evaluate the effect of banded‐P and temporary flooding stress on alfalfa seedling growth in the autumn and subsequent productivity. Experiments were seeded in late August 1994 and 1995 at two locations in Ohio on soils having P levels typical for the region. Fertilizer treatments included no fertilizer P and 27 kg P ha−1 (62 kg P2O5 ha−1) banded under the seed. Flooded and unflooded treatments were imposed 21 to 26 d after seeding. Flooding was maintained for 11 to 18 d, then plots were allowed to drain naturally. Before flooding was imposed, banded‐P increased seedling dry weight by an average of 60%. Flooding reduced seedling dry weight regardless of P treatment. At end of the flooding period, seedlings with banded‐P were larger than the flooded, no‐P controls at three of the four locations. In November, flooded seedlings with banded‐P had greater root dry weight at two locations and greater shoot dry weight at one location compared with the flooded, no‐P controls. Flooding in the autumn reduced dry matter yield the next year at two locations. In 1995, banded‐P increased yield the year after seeding ∼15% in the unflooded treatment at one location and ∼15% in the flooded treatment at the other location. Although banded‐P increased seedling growth in the autumn regardless of flooding treatment, its effect on stand density and yield the year after establishment was minimal.

Effects of Mulch on Soil Moisture and Growth of Desert Willow

The objective of this research was to consider the effects of gravel, wood chip, and tire mulches and turf on soil moisture and root and shoot growth of Chilopsis linearis (Cav.) `Burgundy' (desert willow). Gravel, wood chip, and tire mulches retained greater soil moisture than bare soil (control) with little difference in soil moisture between the mulches. Mulched trees and bare soil had greater height and shoot and root dry weights than trees in turf. Turf conserved soil moisture better than bare soil but appeared to compete with desert willow for water and nutrients resulting in less growth. Trees with gravel and tire mulches had greater shoot dry weight in the second year of growth and greater root dry weight, root length, and root area in both the first and second years of growth after transplanting.

Containerized Jeffrey Pine Growth and Nutrient Uptake in Response to Mycorrhizal Inoculation and Controlled Release Fertilization

Abstract Ectomycorrhizal inoculation with basidiospores of Pisolithus tinctorius and fertilization with two controlled release nutrient formulations, High N 24-4-7 and Sierra 16-6-10 Plus Minors, were evaluated for their effects on containerized Jeffrey pine (Pinus jeffreyi) seedlings. Noninoculated and nonfertilized seedlings and a water soluble fertilizer treatment using Peters 20-10-20 provided for comparisons of mycorrhizal and nutrient amendment effects on growth and mineral nutrition. At 6 months, inoculated seedlings had greater root dry weight while fertilization increased shoot dimensions and weight, with the response to controlled release nutrients exceeding that to water soluble fertilizer. After 12 months, inoculation increased mycorrhizal formation, and inoculated seedlings had greater shoot volume as well as root volume, dry weight, and total length. Controlled release fertilization also promoted greater shoot growth than water soluble nutrients at the final measurement, while root system development was comparable overall among fertilized seedlings regardless of nutrient formulation. Foliar analysis revealed that concentrations of most macro- and micronutrients were sufficient for adequate seedling nutrition in all treatments. However, inoculated seedlings exhibited greater uptake of P, Ca, Mg, S, Fe, Mn, and Zn. Fertilization generally increased foliar concentrations of all of the above elements except Mg and Fe, but also increased N uptake. Overall, these results suggest that inoculation with P. tinctorius and controlled release fertilization with High N 24-4-7 and Sierra 16-6-10 facilitate production of Jeffrey pine container stock suitable for outplanting on harsh sites. West. J. Appl. For. 12(2):33-40.

Pretransplant Temperature Regime and Container Size Alter Strawberry Plant Morphology

Containerized strawberry transplants offer an alternative to problematic bare-root transplants, which often have variability in flowering and vegetative vigor. Containerized transplants were propagated in three different container cell sizes (75, 150, and 300 cm3) and grown at two different temperature regimes for 2 weeks prior to planting (25/15 and 35/25°C day/night). Bare-root transplants from Massachusetts and Florida were graded into small, medium, and large plants based on crown size (8, 12, and 16 mm respectively). Plug transplants grown at 25/15°C had greater root dry weights than transplants grown at 35/25°C. Root imaging analysis (MacRHIZO) showed that the differences in dry weight were due to root area, not root tissue density. Crown dry weight increased with increasing cell size. Plug transplants grown at 25/15°C flowered earlier and had greater production than any other treatment. The 75 cm3 cell size grown at 35/25°C produced greater December strawberry production than larger cell sizes at the same temperature regime; however, the 75 cm3 cell size had decreased January strawberry production while the larger cell sizes had increased production. Larger plug cell sizes had significantly greater production than smaller plugs throughout the season, whereas larger bare-roots had greater production only early in the season. Containerized plug transplants therefore offers a viable alternative to problematic bare-root transplants.

106 INTERMITTENT SPRINKLER IRRIGATION AFFECTS PLANT GROWTH AND N LEACHING

The influence of intermittent and continuous irrigation on the growth, substrate nutrient accumulation and leaching from container-grown marigolds was determined. During a three week period. Tagetes erecta L. `Apollo' in a pine bark substrate received 12 irrigations. Each irrigation allotment was applied intermittently (multiple applications) or continuously (single application). Irrigation occurred when bark reached a targeted water content; irrigation water contained a complete nutrient solution. Leachates were cumulatively collected for each container and analyzed for N; plant dry weight. size, and nutrient composition were determined. Compared to continuously irrigated plants, intermittently irrigated plants had 43% greater root dry weight, 0.7% greater N concentration, and 43% more N leached from the substrate. Shoot mass. size. K, and P concentrations, substrate (pour-through extraction) and leachate N concentration were unaffected by irrigation method. Results demonstrated that. compared to conventional irrigation practices, intermittent irrigation was an effective method to reduce fertilizer effluent and increase N absorption for container-grown plants.

Growth Characteristics and Root Calcium Absorption of Watermelon Seedlings as Influenced by the Fungicides Captan and Thiram

The influence of two fungicides—captan and thiram—on growth and 45Ca absorption by roots of `Starbrite' watermelon [Citrullus lanatus (Thunb.) Matsum. and Nakai] seedlings was investigated. Unilateral application of Ca+2 and Al in agar induced curvature in roots from untreated and pretreated seeds. In untreated seeds, PCMBS inhibited Ca+2- and Al-induced root curvature by 82% and 92%, respectively. In commercially pretreated seeds (captan + thiram), PCMBS inhibited Ca+2- but not Al-induced root curvature. Captan or thiram also inhibited Ca+2- or Al-induced root curvature, and the effects of captan and thiram on root curvature were additive. Serial concentration (0, 0.01, 0.1, 1, 10, or 100 mg·liter-1) tests indicated that captan inhibited 45Ca absorption the most at 100 mg·liter-1, whereas thiram inhibited 45Ca absorption the most at 0.01 mg·liter-1. The effects of captan and thiram on 45Ca absorption were statistically additive. Thiram seemed to influence Ca+2 uptake by affecting exofacial sulfhydryl groups (a mode of action similar to that of PCMBS). DTT reversed the inhibitory effect of thiram on 45Ca absorption by 34% but did not reverse the effect of captan. A field test showed that acidic soil (pH 4.55) reduced leaf number; leaf, stem, shoot, and whole-plant dry weights; and stem length of 15-day-old seedlings. Although there was no difference in root dry weights or root: shoot ratios of plants from pretreated and untreated seeds planted in soil at pH 6.26, planting commercially pretreated seeds in acidic soil produced plants with greater root dry weights and root: shoot dry weight ratios than those from untreated seeds. Seedlings showed a greater response to seed treatment in early growth stages. Captan and thiram may have influenced growth characteristics by inhibiting Al uptake of seedlings planted in acidic soil. To our knowledge, this is the first report on the influence of the fungicides captan and thiram on mineral ion uptake in roots. Chemical names used: p-Chloromercuribenzenesulfonic acid (PCMBS), dithiothreitol (DTT), N-trichloromethylthio-4-cyclohexene-1,2-dicarboximide (captan), tetramethylthiuram disulfide (thiram).

Comparative Studies on Growth and Development of Heat-Tolerant and Non Heat-Tolerant Tomato Plants Grown at Different Root-Zone Temperatures.

Comparative studies on growth and development of young heat-tolerant tomato (Lycopersicon esculentum Mill. cv. Shuki) and non heat-tolerant one (cv. Sataan) grown under four root-zone temperatures (RZT) were carried out. Growth rates were measured at RZT of 15°, 20°, 25°, and 30°C. Plants in study 1, were grown for 10 days (21 to 31 days after sowing) and in study 2, 21 days (21 to 42 days after sowing). Optimum growth in both cultivars occurred at 30°C in plants grown for 10 days and at 25°30°C in plants grown for 21 days. Cultivar 'Shuki' had greater shoot fresh and dry weight, greater root dry weight and greater leaf area than 'Sataan' at all RZT. Cultivar 'Shuki. had greater NAR compared to 'Sataan' at all RZT. Significant and possitive correlations existed among growth parameters at all RZT in both cultivars. Biomass or carbohydrate production between the two cultivars at the end of 21 days was significantly different at RZT of 20°C and 25°C. The results indicate that the heat-tolerant cultivar, 'Shuki', is a better biomass or carbohydrate producer than the non heat-tolerant cultivar, 'Sataan'.

Effects of Hebeloma arenosa on growth and survival of container-grown red pine seedlings (Pinus resinosa)

The ability of the ectomycorrhizal fungus Hebelomaarenosa Burdsall, MacFall & Albers to enhance growth and survival of container-grown red pine seedlings (Pinusresinosa Ait.) was investigated. Shoot height of H. arenosa inoculated seedlings was 28% greater than noninoculated seedlings when grown without fertilizer applications. Eight-week-old seedlings transplanted into a Ball mix (a mixture of peat, bark, and perlite) containing up to a 1:64 dilution of fungal inoculum had significantly greater root dry weights and root/shoot ratios than noninoculated seedlings when grown for an additional 14 weeks. Under experimental greenhouse conditions, root and shoot dry weights of container-grown red pine seedlings that had been directly seeded into Ball mix containing up to a 1:256 dilution of fungal inoculum were significantly greater than weights measured for noninoculated seedlings. Root and shoot dry weights of container-grown seedlings seeded directly into a 1:5 dilution of H. arenosa inoculum and Ball mix and then grown under commercial production conditions were greater than comparable weights of noninoculated seedlings. Hebelomaarenosa inoculation significantly increased seedling survival following outplanting, but did not increase seedling growth. Hebelomaarenosa did not colonize roots growing from the root plug into the surrounding soil.

Effects of Hebelomaarenosa on growth of red pine seedlings in high-fertility nursery soil in Wisconsin

Mycorrhizal colonization and growth of red pine (Pinusresinosa Ait.) inoculated with the fungus Hebelomaarenosa Burdsall, MacFall & Albers were investigated in a highly fertile nursery soil. In greenhouse tests, seedlings became mycorrhizal with H. arenosa when inoculum was incorporated throughout the soil to a 1:256 dilution (v/v). Inoculated seedlings had greater root dry weights and root/shoot ratios than noninoculated seedlings. Seedlings that grew in soil where inoculum had been placed around the seeds had greater root dry weights (at a 1:64 dilution) and shoot dry weights (at a 1:4 dilution) than noninoculated seedlings from unpasteurized or pasteurized soil. Hebelomaarenosa inoculum stimulated increased root and shoot dry weights for 2 years compared with noninoculated seedlings mycorrhizal with indigenous fungi. This study supports the hypothesis that H. arenosa can colonize red pine and cause an increase in growth even in highly fertile nursery soils.

Soil Acidity and Liming Effects on Stand, Nodulation, and Yield of Common Bean

AbstractThe area planted to common bean (Phaseolus vulgaris L.) has been declining in the Southern Mexican State of Chiapas. To determine factors limiting bean productivity in this region, on‐farm experiments were conducted at four locations. Soils were Acrisols (Ustults) at two sites and a Cambisol (Tropept) and Phaeozem (Ustoll) at the other two sites, with pH (H2O) of unlimed soil from 4.6 to 5.0. Insecticide application, genotype, and lime were treatments in a split‐plot design with a factorial combination of two genotypes and 0 or 2000 kg Ca(OH)2 ha−1 as subplots. Across sites, lime addition raised soil pH by 0.4 to 1.3 units, decreased Al saturation by 13 to 38%, and increased extractable Ca two‐to three‐fold. Mean yield without lime was 444 kg ha−1 ha. Insecticide and bean genotype had negligible effects on yield. Lime application resulted in a yield increase of 76 to 313% above unlimed controls across locations. Liming resulted in 40% greater shoot and 18% greater root dry weight, and also improved nodule weight per plant by 110% at early flowering. At maturity, plant density in limed treatments was 23% higher than in unlimed controls, and counts made during the season indicated that soil acidity factors inhibit seedling establishment. Liming also increased pod number per plant by 67%, seed number per pod by 18%, and seed weight by 7%. Increased yield from lime therefore resulted from better stand establishment, and increased seed yield per plant. Increased nodulation and N2 fixation may also contribute to the response to lime.

Establishment and growth of Senecio jacobaea L. and Senecio erucifolius L. in grassland

Summary Senecio erucifolius L. (hoary ragwort) has become conspicuous on roadside verges in southern England. Like Senecio jacobaea L. it is poisonous, so it might be a threat to animal production. In boxed swards the growth of S. jacobaea was less adversely affected by the greater competition from grass with a high level of nitrogen fertilizer than was the growth of S. erucifolius. Also, young S. jacobaea plants showed a much greater ability to regrow after their shoots had been cut at ground level. In a range of grassland managements S. jacobaea established better from seed than did S. erucifolius. Establishment of both species on molehills was poor because of the likelihood that the seedlings would be disturbed or even buried by fresh mole activity. Ten months after sowing, seedlings of S. jacobaea had persisted well in the higher nitrogen environment of ex‐cow‐dung patches, whereas S. erucifolius had not. Under intensive sheep grazing, in the absence of fertilizer, transplants of S. erucifolius had much greater root dry weights than did those of S. jacobaea. Also, in regrowth after cattle grazing on a fertilized sward, S. jacobaea plants had greater shoot dry weights than did S. erucifolius. Thus, although S. erucifolius can establish from seed in bare patches in an intensively grazed sward it is likely to be less persistent than S. jacobaea if the gaps are ex‐dung patches or if nitrogen fertilizer is applied.

DIFFERENTIAL GROWTH AND COMPETITIVE ABILITY OF Amaranthus retroflexus, A. powellii AND A. hybridus

The frequency of occurrence of Amaranthus powellii and A. hybridus relative to that of A. retroflexus in agricultural fields in southwestern Ontario is increasing. Rates of germination and growth and development of the three species were compared at 28/22 °C and 22/14 °C in the growth chamber. Amaranthus powellii exhibited a faster rate of germination and greater early growth with respect to height and leaf number than either of the other species under both temperature regimes. Amaranthus hybridus had a greater root dry weight, took 3 wk longer to reach maturity and produced more seeds than either of the other species. In the field, when sown in pure stands and mixtures at constant density but varying proportions, A. powellii showed a greater competitive ability than A. retroflexus or A. hybridus with respect to number of plants, aboveground fresh weight, and number of seeds produced per square metre.Key words: Pigweed, germination, seed production, competition

INFLUENCE DE LA TEMPERATURE DU SUBSTRAT ET DE LA FERTILISATION AZOTEE SUR LA CROISSANCE, LE DEVELOPPEMENT, LA TENEUR EN AZOTE ET L’ACTIVITE DE LA NITRATE REDUCTASE CHEZ LA TOMATE

We measured the effects of five root temperatures (12, 18, 24, 30 and 36 °C) and five rates of nitrogen fertilization (0, 2.5, 7.5, 22.5 and 67.5 meq N∙L−1) on growth, development, nitrogen content and nitrate reductase activity of tomato plants (Lycopersicon esculentum Mill. ’Vendor’). The greatest root dry weight was obtained at 18 °C and 2.5 meq N∙L−1 and the highest shoot dry weight at 24 °C and 22.5 meq N∙L−1. Total fruit weight was maximum at 24 °C and 2.5 meq N∙L−1. High root temperatures and high levels of fertilization increased the number of aborted flowers and the nitrogen content of shoots, but reduced tomato yields. Nitrate reductase activity (NRA) was higher in leaves than in roots and with plants receiving 22.5 meq N∙L−1 as compared to 2.5 meq. NRA in roots decreased as temperature increased.Key words: Lycopersicon esculentum Mill., root zone temperature, nitrate reductase, nitrogen