Unit Of Dry Matter Research Articles

An assessment of the possible reasons for differential tolerance to fluroxypyr in selected populations of Galium aparine

SummaryIn an investigation of the possible reasons for tolerance lo fluroxypyr by Galium aparine L. (cleavers), a wide range of variation in total herbicide retention was exhibited by nine diverse populations from throughout Europe. Although these differences in fluroxypyr relention became negligible when considered on a unit area basis, a two‐fold difference was maintained per unit dry matter. There was no difference in fluroxypyr uptake between a fluroxypyr‐tolerant and a fluroxypyr‐susceptible population, and differences in translocation between the two populations did not seem to explain the differential tolerance. It is suggested that differential metabolic detoxification may be the main reason for the variation in response to fluroxypyr by populations of G. aparine.

Rye mulch characterization for the purpose of microclimatic modelling

In a field experiment conducted at two locations in Southern Ontario, Canada, during 1989 and 1990, we monitored several rye mulch characteristics including mulch amount, residue area index (RAI), percentage cover, reflectivity and transmissivity of solar radiation. Changes in mulch surface and soil temperatures, and soil water content induced by the presence of a rye mulch were also measured. Empirical functions were obtained to describe (a) initial mulch amount and mulch reduction rate, (b) mulch amount and RAI, (c) change in percentage cover over time, (d) change in short-wave reflectivity over time at various percentages of ground cover, and (e) change in transmissivity with RAI. By obtaining the area of straw per unit dry matter of straw ( A m) and the slope of the linear regression between mulch reduction rate and initial mulch amount, functions were derived to describe the change in mulch characteristics over time. Mulch temperatures differed with mulch amount, warmer at the top and cooler at the bottom of a thicker mulch. Since mulch amount decreased faster for larger mulch rates this difference changed over the season. Soil maximum temperatures in the surface layer were lower under the mulched treatments when compared to the no mulch plots. This difference decreased more quickly over the season for the initially heavier mulch. Soil water contents were higher under the mulched than the no mulch treatment in 1990, with differences decreasing after rainfalls.

Improving plant production by selection for survival at low CO2 concentrations

Abstract Attempts to select C3 plants with slow rates of photo-respiration and increased rates of net photosynthesis have met with little success. This review analyses the properties of mutant genotypes of tobacco (Nicotiana tabacum L. cv. Wisconsin), derived from selection of haploid plants (produced by in vitro mutagenesis of anthers) which survived in CO2 concentrations close to the compensation point. Survivors were diploidized and doubled-haploid plants were self-pollinated to obtain seeds (the selected genotypes). Several glasshouse and field experiments showed that the method of selection at low CO2 concentrations gave genotypes with increased capacity for total dry matter accumulation; increases were similar (mean 24%; range 14–36%) in different conditions for two selected genotypes (SP422 and SP451) when compared to the parental genotype Wisconsin-38. This increase was related to a greater leaf area per plant (mean increase 19%; range 9–43%), to faster photosynthetic rates in mature and old leaves and to similar rates of dark respiration per unit leaf area, but smaller rates per unit dry matter. These changes were related to a greater number of mesophyll cells of smaller size in the selected genotypes. However, the increased productivity could not be related to reduced photorespiration rate or CO2 compensation point nor to improved Rubisco properties (e.g. increased specificity factor) which the selection method was designed to achieve. Selection by survival at low CO2 produced genotypes able to invest more assimilate in growing larger leaves and to maintain a better leaf carbon balance than the parent genotype. These features improved light capture and carbon accumulation and thus increased dry matter production.

Root restriction and N-NO 3 solution concentration effects on nutrient uptake, transpiration and dry matter production of tomato

A previous study found that root pruning reduced tomato plant growth and that increasing the solution nitrate concentration failed to compensate for the pruned roots. The objective of the present investigation was to study the combined effects of nitrate concentration and root restriction on dry matter production, nutrient uptake and transpiration by tomato plants. Root restriction reduced the total dry matter production and the total N and K uptake by tomato ( Lycopersicon esculentum cv. ‘F 121’) grown in a greenhouse in an aero-hydroponic system. However, the flux of N uptake by the roots was higher in the plants with restricted roots. Root restriction did not affect the N concentration but did decrease the K concentration in part of the plant organs. Increasing the solution nitrate concentration from 1.0 to 9.0 mmol 1 −1 significantly increased the nitrate uptake by plants with either restricted or intact roots. The transpiration rate was reduced by root restriction, but the flux of water uptake per root unit volume, the water consumption per unit dry matter production and the transpiration rate per leaf unit area were increased by root restriction. These results were in good agreement with those obtained with pruned roots. It was concluded that the reduction in dry matter production following root restriction was not caused by either N deficiency or water stress.

Carbon dioxide enrichment and temperature effects on cotton canopy photosynthesis, transpiration, and water-use efficiency

The objectives of this study were to evaluate effects of ambient and double ambient [CO 2] at a range of growing temperatures on photosynthesis, respiration, transpiration, water-use efficiency and dry matter accumulation of cotton plants ( Gossypium hirsutum L., cv. DPL 50). In Experiment I, plants were grown outdoors until first bloom, then transferred into naturally lit growth chambers and grown for 22 days at 30/18°C with five CO 2 concentrations varying from 350 to 900 μl l −1. In Experiment II, air temperatures were maintained at 20/12, 25/17, 30/22, and 35/27°C day/night during a 70-day experimental period with [CO 2] of 350 and 700 μl l −1 at each temperature. Photosynthesis increased with [CO 2] from 350 to 700 μl l −1 and with temperature. Plants grown at 35/27°C produced fewer bolls due to abscission compared with plants grown at optimum temperatures (30/20°C). At higher [CO 2], water-use efficiency increased at all temperatures due mainly to increased canopy photosynthesis but also to more limited extent to reduced canopy transpiration. Increased photosynthesis at higher [CO 2] resulted in greater dry matter accumulation at all temperatures except at 20/12°C. Respiration increased as dry matter and temperature increased. Plants grown at higher [CO 2] had less respiration per unit dry matter but more per unit area. These results indicate that future increases in [CO 2] are likely to benefit cotton production by increasing carbon assimilation under temperatures favorable for cotton growth. Reduced fruit weights at higher temperatures indicate potential negative effects on production if air temperatures increase as projected in a high-CO 2 world.

Effects of root pruning and N-NO 3 solution concentration on nutrient uptake and transpiration of tomato plants

Root pruning of tomato plants ( Lycopersicon esculentum cultivar F 121) grown in an aerohydroponic system in a greenhouse resulted in reduced dry matter production. Increasing the solution nitrate concentration failed to compensate for the pruned roots. The objective of the present manuscript was to study the combined effect of root volume and nitrate solution concentration on nitrogen (N) uptake and transpiration. Root pruning decreased the total N uptake per plant, but the rate of uptake per unit root weight was higher in the pruned roots. Analysis of plant organs showed that root pruning did not affect N content per unit dry matter. Increasing the solution nitrate concentration from 1.5 to 9.0 mM increased significantly the nitrate uptake of plants with pruned and intact roots. It seems, therefore, that the reduced dry matter production of plants with pruned roots was not caused by N deficiency. Weekly transpiration was also reduced by root pruning, but the transpiration rate per unit root volume increased after root pruning. The water-use efficiency of the plants was also reduced by root pruning. It was concluded that the reduction in dry matter production following root pruning was not caused by restriction of transpiration.

Pilot and Full Scale Evaluations of Leaves as an Amendment in Sewage Sludge Composting

The use of leaf amendment in woodchips/sludge composting was studied in pilot-scale and full-scale operations. Use of leaves at a rate of 20 percent by volume was compatible with present practices and equipment at the Columbus Compost Facility, but higher rates caused materials handling and curing problems and would necessitate system modifications. Only very slight reduction in new woodchip usage was observed for the 20 percent leaf amendment, but output of sieved-finished compost was doubled. Leaf usage increased airflow requirement per unit dry matter during the initial stage of composting but decreased ammonia release throughout the composting process. On the other hand, use of recycled materials, compost and sieved woodchips, increased ammonia release. Adequate moisture and periodic turning in the pilot-scale studies enhanced composting for all treatments. Leaf usage may necessitate forced aeration during curing to keep full size piles aerobic. In addition, leaf usage increased the total materials handling requirement for operating the full-scale system by 16 percent, and it was concluded that careful consideration of materials handling is the major concern for a system's operating efficiency.

Mechanisms of Tolerance Differences of Potato To Damage By Potato Cyst Nematode (Globodera Pallida)

The growth and yield of three genotypes of potato were compared in replicated plots containing a range of population densities of Globodera pallida, prepared by growing two potato genotypes with different levels of nematode resistance. Plant samples were taken on three occasions, two during the growing season and one to assess final tuber yields. Percentage ground cover was measured on the two mid-season sample dates. The final yields showed that the partially resistant, second early cv. Glenna was much more tolerant of damage by G. pallida than cv. Pentland Dell. In heavily infested plots, the growth of Glenna was reduced initially as much as (in proportional terms), or more than (in absolute terms) that of Pentland Dell. However, because Glenna was more vigorous and produced large haulms, the mid-season reduction in percentage ground cover was much less for Glenna than for Pentland Dell. The third genotype, partially resistant clone 12380, was less vigorous than Pentland Dell, but was not as intolerant as previous reports had indicated. Overall, its intolerance appeared to be due largely to its lack of vigour. Damage by G. pallida slightly reduced the number of stems and the leaf area per unit of dry matter. The factors responsible for the large vigour differences between genotypes in the absence of G. pallida were complicated although differences in number of stems, utilisation of dry matter to produce leaf area and, by implication, photosynthetic efficiency were involved. At low initial population densities (P i ) susceptible Pentland Dell increased the final population density (P f ) much more than partially resistant Glenna and 12380. However, due to competition and root damage, above a P i of c. 40 eggs per g soil, the P f tended to decrease with Pentland Dell. In spite of their moderately high levels of resistance the P i at which 12380 and Glenna decreased population densities was apparently higher at c. 50 and 70 eggs per g soil, respectively.

Growth Analysis of Spring Spinach under the Rowcover.

Growth parameters of spinaches (Spinacia oleracea L.) grown inside and outside of spunbonded polypropylene rowcovers were calculated and compared each other to understand characteristics of plant growth under rowcovers made of poromeric materials. Plants were covered when two leaves unfolded in March. Solar radiation under the rowcover was about 85% of that outside the cover. The rowcover increased mean daily maximum air temperature and mean daily minimum soil temperature by 1.7°C and 0.6°C, respectively.The rowcover enhanced plant growth. Increase in dry matter production rate per unit of dry matter (RGR) under the rowcover brought the rapid growth of covered plants. Larger RGR under the rowcover was due to the increase in dry matter production rate per unit leaf area (NAR) at early growth stage and the increase in leaf area per unit dry matter (LAR) at subsequent stage. Leaf area per unit leaf dry matter (SLA) was affected by the rowcover more than ratio in dry matter of leaf and plant (LWR) . The primary factor of LAR under the rowcover was the increased SLA.

Rates of apparent photosynthesis, respiration and dry matter accumulation in maize canopies

The rates of canopy apparent photosynthesis (PC) and canopy respiration (Rc) were studied during vegetation season in two erectophile and two planophile hybrids of maize (Zea mays L.) grown at two canopy densities [7.5 plants m-2 (HD) and 4.5 plants m-2 (LD)]. Large differences in PC, Rc, RC/PC, leaf area index (LAI), dry matter accumulation and grain yield were found among hybrids and plant densities. Variations in PC and RC were associated mainly with changes in LAI. There was also found change in PC per unit LAI with time. The average RC/PC was 28.9 % for all treatments throughout the vegetation season. PC and RC per unit dry matter were higher in LD than in HD and decreased throughout the measurement period. The HD stand had higher PC and yield in hybrids with erectophile foliage, whereas LD stand had higher PC after male tetrad and got higher yield in hybrids with planophile foliage. Only RC in hybrids of the two foliage types was higher under HD than under LD throughout the vegetation period.

Methane Emission from Livestock in Japan

Relationships between dietary factors and methane production were investigated to predict total methane emission from livestock in Japan. Methane production differed with the type of diet. A high concentrate diet reduced methane production significantly. However, methane production per unit dry matter intake (DMI) was relatively constant. Therefore, Methane production by ruminants could be estimated adequately from DMI alone through 3 species of ruminants and various levels of feeding. From the results of regression analyses, annual methane emission from all livestock including ruminants, pigs and horses was estimated to be 0.35Tg/year in Japan.

Relationship Between Productivity and Phosphate Requirement as a Parameter of Selection in Medicago rigidula (L.) Allioni

Among one hundred lines of Medicago rigidula (L.) Allioni, fifteen (5 high-producing, HP, 5 intermediate-producing, IP, and 5 low-producing, LP) were chosen as experimental material because of their different dry-matter production when grown at 0.5 mg L-1 of P2O5 in hydroponic solution (critical level). The aim of this work was to evaluate the response to selection with respect to dry-matter yield (DMY), made at 0.5 mg L-1 of P2O5 and to check if superior lines could also be isolated when plants were grown at 20 and 200 mg L-1 of P2O5. Results show that HP lines were also superior with respect to DMY (g/plant) at the higher phosphorus concentrations. Highly-productive line selection in M. rigidula can also be achieved when plants are grown at a critical level of phosphorus in the nutrient solution. Phosphate content in the dry matter produced and phosphatase activity were also analysed. Plants of the more-productive lines were characterized by lower phosphate content per unit dry matter and by a higher phosphatase activity.

Effect of low temperatures on 2,4‐D behaviour in maize plants

Summary:The foliar surface of 4‐leaf maize plants was found to be poorly wettable and retained 106 μl g−1 dry matter when sprayed with a U46D (2,4‐D formulation) blank. The third leaf retained 141 μl g−1. A 7‐day cold spell (17/9°C) increased retention per unit dry matter by 53% (135% on the third leaf). Cold stress lowered epicuticular wax quantity by 29% on the third leaf. Contact angles of formulated 2,4‐D lay between 115 and 125° and were not significantly affected by cold stress. 2,4‐D rapidly entered into maize third leaf (66% in 24 h) but migration from it was less than 1.5%. 2,4‐D was readily degraded in maize (80% in 72 h). The most abundant metabolite was probably an ester conjugate; little of the hydroxy derivatives were found. Cold stress reduced 2,4‐D degradation, and 72 h after treatment the amount of undegraded 2,4‐D was 78% higher in cold‐stressed maize plants. It was concluded that 2,4‐D selectivity in maize results from low spray retention per unit dry matter and active degradation of penetrated herbicide. Cold stress affects both factors.

Influence of ammonium on fine root development and rhizosphere pH of Douglas-fir seedlings in sand

Ammonium sulphate is a major component of the air pollutants deposited on forests in the Netherlands. Different amounts of NH4+ were added to Douglas-fir seedlings grown in tall containers of sand, to study the influence of high concentrations of NH4+ in the soil on the development of fine roots and the effects of nitrogen uptake on rhizosphere pH. At the end of this eight-month experiment part of the ammonium appeared to have nitrified into nitrate. High doses of ammonium negatively affected root length and root length per unit of dry matter (specific root length). Although Douglas fir shows a preferential ammonium uptake in nutrient solutions the increases in the pH of the rhizosphere in this experiment indicate that nitrogen was mostly taken up as nitrate. When the ammonium concentration in the soil is low, it cannot be taken up readily because of its low mobility in soil. Shoot growth was stimulated by high availability of nitrogen. The possible effects of high doses of ammonium on long-term forest vitality are discussed.

Laboratory studies of the dynamic behaviour of grass, straw and polystyrene tube during high-speed cutting

Experiments were conducted to study the behaviour of grass and straw stems when cut by sharp and blunt blades at speeds between 5 and 35 m/s; comparative experiments were done with polystyrene tube. Measurements were made of the force and energy during cutting using a piezoelectric force transducer mounted behind the blade on a rotating disc. Stem deflection modes during cutting were recorded photographically by using high-speed film in a camera with an open shutter and firing flash guns sequentially by electronic control, with delay periods ranging from 3 to 425 μs. The lowest speed for efficient cutting (the critical speed) for grass and polystyrene tube was 25–30 m/s. The minimum cutting energy per unit dry matter content for grass with a sharp blade was 55 mJ/mm 2 based on stem wall area. At speeds below the critical speed there was a large stem deflection before cutting was complete, which resulted in long stubble lengths and high cutting energy (up to 400–500 mJ/mm 2 in grass). There was no evidence of a critical speed, however, when cutting straw. The mean peak force for grass per unit dry matter content was 18 N/mm of stem diameter, which was 2.6 times greater than when cutting straw. When cutting above the critical speed for grass (inertia cutting) cutting times were as low as 0.3 ms for the sharp blade, and the stem deflection during cutting was equal to about three stem diameters. For straw, however, the deflection before cutting was complete, represented 8–10 stem diameters, with times of about 1.0 ms. For inefficient cutting at low speeds (c. 5 m/s), cutting times ranged up to 15 ms with stem deflections at the blade of up to 32 diameters for a cutting height of 40mm. The difference between stubble length and nominal cutting height for inertia cutting was about 2 mm for sharp blades but ranged up to 50 mm for inefficient cuts at low speeds. Grass stems showed the widest range of deflection mode immediately after cutting. This varied from stem translation and rotation at low speeds, (c. 5 m/s) to marked bending at intermediate speeds (15–25 m/s) and inertia cutting, with little stem displacement, at higher speeds (>25 m/s). Straw exhibited marked stem translation and rotation with little bending at speeds below 25 m/s but marked bending at higher speeds. Polystyrene tube showed a marked bending over its length at speeds up to 25 m/s, above which cutting was in the inertial mode. The minimum cutting energy for grass stems was three times that required for quasi-static cutting in shear. At low cutting speeds (<12m/s) about 65% of the energy was utilized in overcoming friction. For straw, however, the frictional component was generally relatively low (5–10%) and stem kinetic energy was equal to about 20% of the total energy input. The specific cutting energy was twice as large for the blunt blade as for the sharp blade in grass and straw. The difference between stubble length and nominal cutting height was generally about three times greater when using the blunt blade.

Intake, rumination, reticulo-rumen fluid and particle kinetics, and faecal particle size in heifers and cattle fed on grass hay and wilted grass silage

Grass hay and prewilted grass silage were supplied to heifers and mature cows at restricted and ad libitum level. Neutral detergent fibre (NDF) contents were 64.5 and 448.5% in dry matter of hay and silage, respectively. Voluntary feed intake decreased with increasing cell wall content, but time spent ruminating increased, and so did transit time of digesta in the lower gut and mean faecal particle size. Rumen motility was most intensive after feeding silage. Relative to ad libitum, at a restricted level of feed intake the time spent ruminating per unit of dry matter or the NDF ingested increased, fractional rates of reticulo-rumen emptying of particles did not change, transit in the lower gut slowed down, and faecal particles became smaller. Variation in voluntary feed intake between individual animals could for a significant part he accounted for by NDF content of the diet and time spent ruminating.

Shade Effects on Growth of Tall Fescue: I. Leaf Anatomy and Dry Matter Partitioning

Irradiance influences plant growth through photosynthetic activity and developmental responses. Our objectives were to determine the effect of irradiance on leaf anatomy and dry matter partitioning of tall rescue (Festuca arundinacea Schreb.). Plants were grown outdoors for 10 wk during summer 1986 and autumn 1987 with or without screencloth to give irradiances of 30% (low), 60% (medium), or full (high) sun. Data were similar for both years, although daily air temperatures averaged 25°C in 1986 and 12°C in 1987. Production of total plant dry matter was reduced at low irradiance, primarily due to fewer tillers per plant. Shoot/root ratio and leaf area ratio (leaf area per plant dry weight) were higher for plants grown at low irradiance than for those grown at high irradiance. Recently developed leaf blades on plants at low irradiance were 54 or 650/0 longer and had 56 or 77% more leaf area, but were 12% thinner and had 18 or 25% lower specific leaf weight than did those grown at high irradiance. Blade width was not affected. Total stomatal density at low irradiance was 17 or 24% lower than at high irradiance, with a larger reduction on the adaxial than on the abaxial epidermis. Proportional cross‐sectional areas of epidermis and bulliform cells, vascular bundle and fiber cap cells, and mesophyll cells were similar over treatments. Blades grown at low irradiance had ≈25% more air space than did those at high irradiance. At low irradiance, partitioning of dry matter among plant parts and developmental processes within the leaf blade were shifted to favor production of leaf blade area per unit of dry matter with no influence on forage quality.

Root Respiration and Growth in Plantago major as Affected by Vesicular-Arbuscular Mycorrhizal Infection

Effects of vesicular-arbuscular mycorrhizal (VAM) infection and P on root respiration and dry matter allocation were studied in Plantago major L. ssp. pleiosperma (Pilger). By applying P, the relative growth rate of non-VAM controls and plants colonized by Glomus fasciculatum (Thaxt. sensu Gerdemann) Gerdemann and Trappe was increased to a similar extent (55-67%). However, leaf area ratio was increased more and net assimilation rate per unit leaf area was increased less by VAM infection than by P addition. The lower net assimilation rate could be related to a 20 to 30% higher root respiration rate per unit leaf area of VAM plants. Root respiration per unit dry matter and specific net uptake rates of N and P were increased more by VAM infection than by P addition. Neither the contribution of the alternative respiratory path nor the relative growth rate could account for the differences in root respiration rate between VAM and non-VAM plants. It was estimated that increased fungal respiration (87%) and ion uptake rate (13%) contributed to the higher respiratory activity of VAM roots of P. major.

Regulation of NADP-dependent Glutamate Dehydrogenase during Morphogenesis of the Ascomycete Sphaerostilbe repens

The Ascomycete Sphaerostilbe repens differentiates successively two series of coremia and rhizomorphs in pure culture. The first group appears between 36 and 84 hours of incubation and the second is formed from the seventh day of culture on. In the interval, the fungus only gives rise to vegetative mycelium. NADP-dependent Glutamate dehydrogenase (E.C.1.4.1.4) was purified to homogeneity and specific antibodies were used to quantify the enzyme by immunoelectrophoresis during morphogenesis of the fungus. Molecular activity of NADP-GDH which denotes the relative activity per enzyme molecule was at a high level during the differentiating periods and decreased when the colony grew only as vegetative mycelium. Concentration of the enzyme in the thallus, expressed with respect to dry matter or to soluble proteins, varied in the opposite way, passing through a maximum on the sixth day of culture. However, molecular activity and synthesis of the enzyme did not compensate each other. Indeed, NADP-GDH activity per unit of dry matter, which attained a maximum during vegetative growth, was closely correlated with the amount of the enzyme in the tissues.

Effect of carbon dioxide on sorghum yield, root growth, and water use

The concentration of atmospheric carbon dioxide (CO 2) is rising. The effect of higher than ambient levels of CO 2 on plants grown in the sub-humid central Great Plains of the U.S.A. has not been investigated. Therefore, an experiment was conducted at Manhattan, Kansas, to study the effect of elevated levels of CO 2 on grain sorghum [ Sorghum bicolor (L.) Moench]. During the summer of 1984, the sorghum was grown in rhizotrons in which root and shoot growth could be monitored throughout the growth cycle. The tops of the plants were enclosed in plastic chambers, which contained one of four concentrations of CO 2 : 330 (ambient), 485, 660, and 795 μl 1 −1. Enriched CO 2 delayed the boot, half bloom, and soft dough stages. Sorghum grown at elevated concentrations of CO 2 yielded more roots and shoots than plants grown with 330 μl 1 −1. At all soil-profile depths, root numbers and weights were higher at elevated CO 2 than at ambient CO 2. However, water use per unit dry matter of leaf, stem, root, and grain was decreased 13, 30, 31, and 29%, respectively, in plants grown at 795 μl 1 −1 CO 2 compared to plants at 330 μl 1 −1 CO 2. Although elevated CO 2 levels increased the stomatal resistance and leaf temperature, an increase in leaf area indices resulted in a lower canopy resistance.