Rate Of Increase In Height Research Articles

Phenology and Tiller Characteristics of Big Bluestem and Switchgrass Cultivars in a Short Growing Season Area

AbstractWarm‐season grasses are increasingly being cultivated in North America for summer forage and biomass production. The cooler temperatures and shorter growing seasons typical of Canadian production areas, are major limiting factors to warm‐season grass production in these areas. This research assessed the morphological development and relationship of growing degree‐days (GDD) to plant morphology and tiller characteristics in nine cultivars of switchgrass (Panicum virgatum L.; Blackwell, Cave‐in‐Rock, Dakota, Forestburg, Pathfinder, Shelter, Sunburst, ND3743, and New Jersey 50) and in ‘Niagara’ big bluestem (Andropogon gerardii Vitman). The study was conducted for three years on a St. Bernard sandy clay loam (Typic Hapludalf) in southwestern Quebec. Stand cover, plant morphology, tiller number, height, and diameter, and leaf number per tiller were all assessed during the season. All entries persisted through the three years of the study and showed increases in tiller number (from an average of 565 to 683 m−2) from one year to the next. Dakota, Cave‐in‐Rock, and Shelter switchgrass had the highest ground cover ratings after three years (85, 85, and 84%, respectively). Dakota, ND3743, and Forestburg were early maturing; New Jersey 50 was the latest in maturity. Niagara big bluestem had the tallest tillers (183 cm) and largest rates of increase in height (2.8 cm d‐1), followed by Cave‐in‐Rock (2.0 cm d−1) and Blackwell (1.9 cm d−1). The shortest tillers were recorded for Dakota (111 cm) and ND3743 (118 cm). Changes in leaf number per tiller with GDD were best described by quadratic regression models (r2 = 0.80‐0.97). These models were stable over two years. Cultivars varied in the number of GDD required for maximum number of leaves per tiller, with later‐maturing cultivars generally requiring greater GDD accumulation. These data indicate that warmseason grasses can be grown successfully in eastern Canada.

Modelling fungal growth on surfaces.

Fungal growth in time and space at the substrate surface was modelled for a simple system mimicking solid-state fermentation, using a polycarbonate Nucleopore membrane laid over a glucose solution. Biomass production depends on both tip density and the diffusion of glucose within the fungal hyphae. The model predicts early increases in both height and concentration, followed by a period in which the biomass profile moves with a constant wavefront. The rate of increase in height increases as tip diffusivity increases or as the Monod saturation constant for glucose decreases.

Physical activity and four-year development of back strength in children.

Physical activity in children is important, both for its direct benefits and for establishing potentially lasting future behaviors. Understanding the development of back strength in children is also important, because decreased back strength is associated with low back pain in adults. We hypothesized the following: (1) a substantial percentage of children do not participate in adequate physical activity; (2) the development of back strength corresponds to the development of strength of appendicular muscles; (3) there is a positive relationship between physical activity and back strength. The study included 53 boys and 43 girls, aged 10 to 19 yr, who had undergone isometric strength testing 4 yr previously. From responses to a questionnaire, each child's level of physical and sedentary activity was calculated. Isometric back flexion and extension were measured with the same method used 4 yr previously. Statistical analyses were performed, including quadratic regressions to estimate the rate of increase in strength, height, and weight. The following results were found: (1) during the month before testing, 21 children participated in physical activity for less than 30 min/day; (2) the level of physical activity was significantly associated with back flexion and back extension (P = 0.03 for both); (3) the peak rate of increase in back strength occurred approximately 1 yr after the peak rate of increase in height. We conclude the following: (1) measures should be taken to increase the involvement of children in athletic activities; 2) physical activity may be important in the development of back strength; (3) the pattern of back strength development seems to be the same as that for development of muscles of the appendicular skeleton.

Seasonal variation in growth characteristics of Lolium perenne and Trifolium repens in swards under different managements

AbstractIn a range of perennial ryegrass/white clover swards, variation in the surface heights of the grass and clover components, the rates of increase of these surface heights and the specific leaf areas (SLAs) of ryegrass and white clover were described for 1 year. The swards were of an early‐ or late‐flowering (Aurora or Melle respectively) perennial ryegrass variety growing with either a small‐ or a medium‐leaved (Kent or Milkanova) white clover and were either continuously stocked by sheep or continuously stocked apart from a rest period in April‐May (Aurora) or May‐June (Melle).The surface heights of grass and clover were not affected by the variety of their companion species, and the surface heights of the two clover varieties were similar. The grass was always taller than the clover, although the magnitude of the difference between the species varied with time of year and the timing of the rest period.Before the summer solstice the rate of increase in height of grass was greater than that of clover except at cool temperatures (5°C) and warm temperatures (16°C), and in the unrested Melle sward. After the solstice the rates of increase in height, particularly of clover, were lower than the rates seen at similar temperatures before the solstice.Overall, the SLAs of both clover varieties were greater than those of ryegrass when grown with Aurora but not when grown with Melle, and the SLAs of both species increased during the year. By October the SLAs of both grass varieties were less than those of their companion clovers.The results are discussed in relation to their implications for the species composition of the swards.

Soybean Flower Production as Related to Plant Growth and Seed Yield

Flowers are directly related to seed yield through the fruits that form from flowers, but the physiological factors that regulate flower production after induction of the flowering state are not well understood for soybean [Glycine max (L.) Merr.], where the connection of flowering to yield is complicated by abortion of potential fruits. The objectives of this research were to (i) evaluate methods of obtaining flower count data and characterizing flowering in terms of rate of flower production (FRATE), duration of flowering (FPERIOD), and total flowers (FTOTAL) in soybean genotypes differing in numbers of flowers and levels of reproductive abortion; (ii) determine relationships between these characteristics and seed yield; and (iii) measure effects of plant factors on the flowering characteristics when both plant growth and flowering are altered by variation in planting date. Growth and flowering were measured in five plantings during 2 yr at Brookings, SD in Vienna (fine‐loamy, mixed Udic Haploboroll) soil, using cultivars Dassel and Corsoy 79, which have few flowers per raceme, and the many‐flowered lines SD87001 and IX93‐100. Flowering was measured by counting blossoms three times weekly throughout the bloom period (Method I) and by counting fruits and abscission scars for aborted flowers 2 wk after final blossoming (Method U). Cumulative flowering curves determined by Method I were closely fit by the logistic function. Total flowers by Method I was lower than by Method II, but only minor differences were observed between methods for detecting flowering differences caused by planting date or genotype. Flowering traits measured by Method I accounted for 60 to 77% of the variation in seed yield. Genotypes differed markedly in the relationship of plant characteristics to flowering traits, but rate of increase in height in vegetative stage generally had significant negative correlation to FPERIOD, had positive correlation to FTOTAL and FRATE, and was identified as one of several factors that had major influence on flowering traits. It is concluded that large and rapidly growing soybean plants tend to have short FPERIOD with high FRATE and FTOTAL, but genotypes also may have additional traits that determine flower production characteristics.

A longitudinal study of tooth growth in a single individual based on long‐ and short‐period incremental markings in dentine and enamel

AbstractGround sections of teeth from a single individual revealed approximately 30 fluorescent lines in the dentine resulting from successive courses of tetracycline antibiotics given over a period of approximately 12 years. In addition, many teeth showed long‐period incremental markings in the dentine. Short‐period daily cross‐striations in the enamel were used to calculate the periodicity of the long‐period incremental lines in both enamel and dentine. The incremental markings in the dentine were then used to calibrate the time of administration of each of the courses of tetracycline antibiotics. Enlarged micrographs of the teeth, constructed using fluorescence microscopy, were used to measure the increase in height of different teeth throughout the growth period on each occasion the tetracycline antibiotics were given. The times of initial mineralization of the teeth and the duration of crown formation were also determined for each tooth section. Line plots of tooth height against age were computed and used to calculate the rate of increase in tooth height during crown and root formation for one example of each tooth type. Initial rates of increase in height during enamel apposition and coronal dentine formation were fast, between 10 μm and 14 μm per day. During the latter phase of crown formation and during early root formation, tooth height increased at a slower rate of between 4 μm and 6 μm per day. Rates of increase in tooth height then rose to between 13 μm and 26 μm per day during the second half of root formation before falling off to a rate of approximately 4 μm per day during root completion (as the root apex formed). The times of initial crown mineralization and the total crown formation times estimated in this individual were all within the range known for modern humans but there was comparatively early mineralization of the third permanent molar. These findings are discussed in the context of other studies on human dental development.

Growth and developmental patterns in Prader-Willi syndrome.

Eleven Japanese patients with Prader-Willi syndrome were studied from infancy, and examined with respect to their growth and development. The chromosomal aberration was observed in 40% of the patients using a high-resolution chromosome banding technique. The birth weight in 10 out of the 11 patients was below the mean and the rate of body weight gain was severely retarded by 6 months in all cases, which suggested an insufficient utilization of nutrients in uterine life and in early infancy. The rate of height increase as well as that of body weight increase were also transiently retarded from 10 to 18 months of age in eight cases, and the body weight gain increased dramatically after 10-18 months due to hyperphagia. The patients' mean milestones of development were delayed (the mean developmental quotient was 50) in comparison with those of control patients; there was no difference between the developmental milestones of the two groups with and without the chromosomal aberration.

Rooting Depth and Dry Matter Development of Sunflower

AbstractThe use of modeling and computers increases the potential to estimate crop water use and irrigation requirements. However, for that potential to be realized, data on root growth are needed for model development and/or input. Few field studies have included direct measurement of sunflower (Helianthus annuus L.) root development. Our objective was to examine plant development, with emphasis on rooting depth, of field‐grown sunflower. The study was in 1985 and 1986 near Manhattan, KS on deep, barrier‐free, Muir silt loam soil (fine‐silty, mixed, mesic Cumulic Haplustoll). Regression analysis was applied to data on root growth and aboveground development. The resulting equations were then used to examine growth patterns and rates of development. Canopy height reached its maximum of 2.40 m during the latter part of disk flowering. The maximum rate of height increase was 72 mm d−1 and occurred during early bud formation. Roots reached the deepest soil depth of 2.18 m late in the growing season (95% of the total of thermal units from emergence to physiological maturity). Roots reached 1.88 m at the beginning of disk flowering and 2.02 m at the completion of disk flowering. Rate of advance of the deepest observed root decreased linearly from 43 mm d−1 during mid June (eight leaves emerged). Green leaf area index (LAI) reached its maximum immediately prior to disk flowering. Dry mass of leaves, stems, and heads reached maximums at late disk flowering, back of head yellow with bracts still green, and physiological maturity (no green on head), respectively. Total aboveground dry mass reached its maximum at 85% of the total of thermal units from emergence to physiological maturity. The rate of total aboveground dry mass yield was greatest near mid season (48% of total thermal units). The data on sunflower rooting depth reported in this article will assist in estimation of crop water use.

Equine osteochondrosis in the '90s

The International Seminar on Equine Osteochondrosis in the '90s was held September 28-30th at Girton College at Cambridge, England. Synopses of some of the presentations follow: Dr. R. R. Pool, of the School of Veterinary Medicine at Davis, California said the need for a more precise definition differentiating primary (idiopathic; genetic) from secondary (acquired) developmental lesions of the equine osteochondral complex is obvious. Truly primary equine osteochondrosis (EOCD) should be characterized by multiple random cartilage lesions in physes and articular surfaces in multiple skeletal sites. Lesions should not be bilaterally symmetrical. B. H. Thorp, of the Institute of Animal Physiology and Genetics Research, at Midlothian, Scotland described a potential model for EOCD, avian tibial dyschondroplasia (ATD). ATD and EOCD are both characterized by the presence of a largely avascular mass of cartilage composed mostly of partially hypertrophied (transitional) chondrocytes and abnormal interlacunar matrix. The hypothesis that ATD is a consequence of aberrant or incomplete chondrocyte differentiation may be supported by evidence that genetic selection forATD results in accumulations of transitional chondrocytes. Deficiencies in TGF-13 and c-myc gene products and a shift to increased fully hypertrophied chondrocytes resuits from a defect or defects in gene translation. It was suggested that similar metabolic approaches replace the current reliance on morphologic investigations in attempts to define the pathogenesis and possible etiology of EOCD. Dr. C.W. Mcllwraith, of Colorado State University said there are 3 classes of EOCD lesions: those showing both clinical and radiographic signs, those showing only arthroscopic signs, and those showing only radiographic signs. EOCD lesions are usually bilateral inthe femoropateUar and tarsocrural joints and quadrilateral in the fetlock joints, and occur most commonly at the margin of excursion of one articular surface on another. These findings are consistent with the existence of a window of vulnerability to biomechanical insult in the development of certain joints. N. E. Dolvik, Norwegian College of Veterinary Medicine reported that radiographic examination during 1989 of about 60% of all Standardbred trotters born in Norway in 1988 showed an incidence of tibiotarsal EOCD of 14.3% and of bony fragments in the palmar/ plantar portion of the metacarpophalangeal or metatarsophalangeal joints of 11.8%. The heritability coefficient of tibiotarsal EOCD was estimated to be 0.32 ± 0.12 (r 2 -0.13), and that of bony fragments in the palmar/plantar portion of the metacarpophalangeal or metatarsophalangeal joints was estimated to be 0.13 ± 0.08 (r 2 0.09). B. Sandren and J. Philipsson, of the Swedish University of Agricultural Sciences reported that radiographic examinations of the tarsocrural and metacarpophalangeal and metatarsophalangeal joints of 793 long yearling Standardbreds revealed an incidence of tarsocruununited palmar/plantar eminences in the fetlock joints of 4.2%. Most tarsocrural EOCD 95% occurred at the intermediate ridge of the tibia. Bony fragments and ununited eminences occurred mainly in the hind limbs. Most (75%) bony fragments were found in the medial regions of the fetlock joints, while ununited eminences were usually found laterally. Horses with ununited eminences had a much higher incidence of bony fragments within the fetlock joints. The heritability of tarsocrural EOCD was estimated to be 0.24 ± 0.18, and that of bony fragments in the fetlock joints was estimated to be 0.17 ± 0.13. Height at the withers was inversely correlated with the appearance of bony fragments in the fetlock joints (r ~= -0.12) and tarsocrural EOCD (r 2 = -0.51). Carpal circumference also was inversely correlated with the appearance of bony fragments in the fetlock joints (r ~ = 0.40); in contrast, carpal circumference was positively correlated with the presence of tarsocrural EOCD (r 2 = 0.91). TarsocruralEOCD and bony fragments in the fetlock joints were positively correlated (r 2 = 0.60), indicating that perhaps one-third of the genes involved as causative factors may be the same for both types of lesions. L.R. Bramlage, of Rood and Riddle Equine Hospital of Lexington, Kentucky said that foals followed from birth to 180 days of age exhibited little correlation between rates of increase in height (r = 0.24) or body weight (r = 0.14) and the number of EOCD-like cartilage defects discovered during gross examination at necropsy. Neither growth rates nor lesion frequency were correlated with dietary copper intake.

Serum Transferrin as a Marker of Bone Growth in Boys: Correlation with Serum Alkaline Phosphatase Activity, Plasma Insulin-Like Growth Factor 1 and Rate of Growth in Height

Transferrin (TF) has a growth promoting activity in cell culture. The aim of this work was to study possible relationships between serum TF, alkaline phosphatase activity (ALP), plasma insulin-like growth factor 1 (IGF-1) levels and rate of height increase in boys. 149 boys aged 13-15 yrs were studied. TF levels were measured using turbidimetric method. The serum levels of ALP could be used as a biochemical marker for bone formation. Significant correlation was found between serum TF levels and ALP levels (r = 0.31, P less than 0.0005). The TF levels are higher in iron-deficiency anemia. The hemoglobin (Hb) and serum ferritin were measured in all boys. Thirty-one of 149 boys had no iron-deficiency anemia (Hb 14.0 g/dl and serum ferritin 23 ng/ml). The rate of growth in height was estimated over a 5 month period. In these boys, the rate of growth in height was significantly correlated with serum TF levels (r = 0.37; P less than 0.05). A significant correlation was found between serum TF levels and plasma IGF-1 levels (r = 0.45; P less than 0.05). These data indicate that serum TF levels may be a marker of skeletal growth in normal boys.

Growth and water use of faba beans ( Vicia faba) in a sub-humid climate I. Root and shoot adaptations to drought stress

Root growth, shoot growth and water-use of faba beans ( Vicia faba L.) were studied to ascertain the nature and timing of morphological adaptations to drought stress. Spring-sown crops were grown in an alluvial silt loam in Canterbury, New Zealand, during 1982/83. Extractable water capacity for faba beans in this soil is about 120 mm. The crops were either irrigated frequently to avoid drought stress ( I f treatment) or not irrigated at all ( I o treatment). Grain-yields were 3.8 and 2.9 t ha −1 respectively for the I f and I o crops. Actual soil water-deficit, potential soil water-deficit, soil matric potential at 0.2 m depth, periodic evapotranspiration, and crop height increase were used as indices of drought stress. From around day 70. all the drought-stress indices were greatest in the I o crop. The I o crop responded to stress by reducing its rate of height increase (from about day 70), decreasing its rate of leaf-area expansion slightly (between days 69 and 81), greatly increasing root growth (from about day 78), producing leaves of smaller specific area (from around day 80), and shedding leaves (from around day 94). Radiation conversion efficiency was about 9% greater in the I o treatment. Drought-stress had no detectable effects on shoot dry-matter until after day 120. Thus the observed adaptations were reasonably successful in reducing the drought stress experienced by the I o crop. Furthermore, all these adaptations occurred during flowering and pod-fill, periods suggested by some authors to be when faba beans are especially sensitive to drought. Our results offer some explanation for previous results which suggest faba bean yields are equally sensitive to drought stress during all developmental phases.

Survival, regrowth and rubber production of clipped guayule plants: Effects of irrigation regime, season and line

Guayule (Parthenium argentatum A. Gray) plants of USDA lines 11604,12229 and 11591 were subjected to irrigation regimes of 300,450, and 650 mm/per year and clipped at different ages over a period of several years. Survival, regrowth rates, biomass production, and rubber and resin accumulation in the plants after cutting at ground level were monitored. A survival rate of 92-100% was recorded in plants clipped in February (end of the dormant period) or October (just before the dormant period). In plants cut in summer (July) survival was less and presumably dependent on plant water status and age. No significant differences were evident among the different lines. The best plant development as determined by rate of height increase occurred in plants clipped in February. Total biomass production and total rubber yield (rubber or biomass at the time of cutting plus rubber or biomass at the second harvest) were lower in clipped than in unclipped plants. The reduction in rubber yield was most pronounced in plants of the medium and high water treatments.

A dynamical model of lava flows cooling by radiation

The behaviour of a lava flow is reproduced by a two-dimensional model of a Bingham liquid flowing down a uniform slope. Such a liquid is described by two rheological parameters, yield stress and viscosity, both of which are strongly temperature-dependent. Assuming a flow rate and an initial temperature of the liquid at the eruption vent, the temperature decrease due to heat radiation and the consequent change in the rheological parameters are computed along the flow. Both full thermal mixing and thermal unmixing are considered. The equations of motion are solved analytically in the approximation of a slow downslope change of the flow parameters. Flow height and velocity are obtained as functions of the distance from the eruption vent; the time required for a liquid element to reach a certain distance from the vent is also computed. The gross features of observed lava flows are reproduced by the model which allows us to estimate the sensitivity of flow dynamics to changes in the initial conditions, ground slope and rheological parameters. A pronounced increase in the rate of height increase and velocity decrease is found when the flow enters the Bingham regime. The results confirm the observation according to which lava flows show an initial rapid advance, followed by a marked deceleration, while the final length of a flow is such that the Graetz number is in the order of a few hundreds.

Pubertal growth spurt induced by human chorionic gonadotropin in hypogonadotropic growth hormone-deficient children.

Eight hypogonadotropic growth hormone-deficient children were treated with human chorionic gonadotropin (HCG) while they continued to receive a fixed dose of HGH for a one year period. They were observed for changes in somatomedin C (IGF-I) and height increase velocity. Mean somatomedin C was 0.79 +/- 0.30 U/ml in normal prepubertal children (N = 7) and 0.78 +/- 0.31 U/ml in prepubertal normal short children (N = 22). At pubertal stage 3, somatomedin C was 2.21 +/- 1.23 and 2.05 +/- 0.44 U/ml in normals (N = 5) and in normal short children (N = 7), respectively. When 3000-5000 units/week of HCG were given to each of the 8 hypogonadotropic growth hormone-deficient children who were receiving HGH at a mean dose of 0.33 +/- 0.05 IU/kg/week, testosterone increased from less than 0.3 ng/ml to more than 5 ng/ml at 6 months in 3 cases and at 12 months in 2 cases, while the testosterone concentration was less than 3.5 ng/ml in the remaining 3 cases. The rate of height increase rose significantly (p less than 0.001) from 5.2 +/- 1.0 to 9.3 +/- 1.4 cm/year mimicking the normal pubertal growth spurt. However, the mean somatomedin C concentration was 0.44 +/- 0.23 before therapy, 0.33 +/- 0.30 at 6 months and 0.31 +/- 0.14 U/ml at 12 months after the start of HCG therapy. It is concluded that the pubertal growth spurt induced by HCG in hypogonodotropic GH-deficient male children is not mediated by the increase in somatomedin C production.

Growth of yeast colonies on solid media.

Colonies on nutrient agar of the aerobic yeast Candida utilis show linear increases in diameter and height with time throughout most of the growth cycle. The concentration of glucose in the agar has a negligible effect on radial growth rate although an increase in the glucose concentration prolongs the linear radial growth phase. The rate of increase in height of the colony is proportional to the square root of the initial glucose concentration. A new model that considers both glucose diffusion and oxygen diffusion in the colony is consistent with the observed colony profiles.

Weight gain and height velocity during prolonged first remission from acute lymphoblastic leukaemia.

A retrospective analysis of the medical records of 86 children in prolonged remission from acute lymphoblastic leukaemia was performed to calculate changes in the rate of increase in height and weight gain. The rate of increase in height decreased during initial treatment, and the potential for final adult height was not regained. Weight gain was excessive; this started during treatment and persisted into the remission years. Values of weight adjusted for height did not return to values found before treatment until eight years after diagnosis. Several factors can account for this weight gain, but there is a practical need to provide dietary advice, particularly when chemotherapy is stopped.

The influence of nutrition and temperature on the growth of colonies of Escherichia coli K12.

Growth of Escherichia coli was faster in liquid cultures than on the same medium solidified with agar. Colony profiles indicated a common basic structure with a size variation due to nutritional conditions. Radial growth rates were linear and height also increased approximately linearly, especially in the early part of the growth period. The ratio of rate of height increase to diameter increase depended on nutrition. Conditions favouring rapid growth led to faster radical growth relative to height increase. A rise in incubation temperature led to increases in height and in diameter: however, diameter increased relatively more than height. These results are discussed in terms of the structure of the colony.

Observations on the growth rate inMartesia striata (Linn.), the wood-boring pholad in the cochin harbour region on the south-west coast of India

Experimental studies conducted in Cochin harbour during 1967 to 1969 have shown thatMartesia striata settled on timber test panels during the months December to May when the salinity of water varied from 28·2‰ to 34·0‰ and temperature from 29·4° C to 32·5° C. The maximum size of the animals in one month old panels varied from 2·0 mm to 6·0 mm. The rate of growth in the second, third and fourth months varied from 6·0 mm to 16·0 mm; 4·0 mm to 19·0 mm; and 1·0 mm to 7·0 mm, respectively. The average growth rates calculated for the second, third and fourth months showed that the growth was rapid in the second and third months with the maximum in the third month. No definite correlation between the rate of growth and the hydrographic conditions was perceptible. The pattern of growth in the species was found to follow Bertalanffy’s equation. The length-height relationship during the course of growth inMartesia striata showed that in early stages up to 3 mm size, the length of the animal was equal to its height and as growth progressed the rate of increase in height gradually diminished and in large specimens the height measured only about half the length of the animal.

Testing of the concrete placing complex on the Chirkeisk Hydroelectric station

1. A test of a concrete placing complex, the basis of which is a mechanized peripheral rig, showed its technical-economical effectiveness. 2. With a section-sized rig which is movable from layer to layer without dismantling and with the small stationary cranes, network of engineering services, auxiliary equipment for work inside the block and a light tent located on it, concrete placement in a dam approaches conditions of concreting at a stationary industrial plant. 3. In concreting with the rig the time for a complete cycle can be brought down to 3.5–4 days and the rate of increase in height of the structure to 12–13 m per month. 4. The output in pouring concrete with the rig can be brought up to 8–10 m3 per man-day. 5. Twenty-five ton cable cranes with 500-m spans controlled by radio operate steadily and the attained parameters correspond to design characteristics. 6. The radio directed 8-m3 bucket basically meets the presented requirements but needs improvement in the construction and the placement of the vibrator and a change in the design of the door to eliminate its unintentional opening.

Rate of Weed Root Elongation

Considerable differences in rate of root elongation were observed. Species studied in order of decreasing rate root elongation were cocklebur (Xanthium pensylvanicum Wallr.), palmer amaranth (Amaranthus palmeri S. Wats.), barnyardgrass (Echinochloa crusgalli (L.) Beauv.), buffalobur (Solanum rostratum Dunal), kochia (Kochia scoparia (L.) Schrad.), crabgrass (Digitaria sanguinalis (L.) Scop.), sorghum (Sorghum vulgare L., var. RS 610), Russian thistle (Salsola kali L., var. tenuifolia Tausch), and tumblegrass (Schedonnardus paniculatus (Nutt.) Trel.). In 15 days, cocklebur and tumblegrass roots grew 33 and 11 in, respectively. With all species, the rate of root elongation always exceeded the rate of height increase. There was poor correlation between rate of root elongation and weed height, top weight, and root weight.