Dry Weight Data Research Articles

Growth Analysis of `Daliva' Chicory Grown Under Bare Soil or Straw Mulch Conditions

Some chicory (Cichorium intybus L.) cultivars, especially early and extra-early cultivars, often bolt and flower the first year of growth, contrary to the expected behavior of biennials. The extra early hybrid cultivar `Daliva' was grown in the field under bare soil and straw mulched conditions to examine possible correlations between growth rates, leaf and root sizes and bolting. Plants, sown on 19 June, were harvested weekly from 4 July to 1 Oct.; a total of 14 harvests. Root variables of length and diameter were best described by linear equations but root dry weight was decidedly quadratic in response. Leaf number, area and dry weight and crown diameter data were fitted to the Richards function to describe their sigmoidal phases of growth. In most cases, when using the Richards function, the two treatments (mulch vs. no-mulch) required different parameters to fit a line to the observed points with r2 values >0.95. A statistical comparison between treatment parameters (as obtained from SAS PROC NLIN and SigmaPlot) will be discussed.

Effect of Wind and Soil Moisture on the Growth of `Bluecrop' (Vaccinium corymbosum L.)

This study was conducted in the greenhouse by running two experiments at different temperature regimes (22°C day and 13°C night and 33°C day and 22°C night). One-year-old tissue culture propagated plants were irrigated at three different soil moisture tension levels (5, 15, and 30 cnbars) and either exposed to moving or still air. The moving air treatment was created by two 51-cm-diameter fans running at either low (5.6 mph) or medium (8.2 mph) speed. Each experiment included, forty-eight plants arranged in a randomized complete block design. Each block consisted of a greenhouse bench containing two fans, a plastic dividing wall and two plant replications for each treatment. Canopy volume measurements were taken at the beginning, middle and end of each experiment to estimate growth rate. At the end of each experiment, total leaf area and leaf, stem and root dry weight data were collected. In the moderate temperature experiment, the still air treated plants had the highest canopy volume and leaf weight ratio while the moving air treated plants had the highest stem weight ratio. The only difference for the moisture treatments was the 5-cnbar treatment had the highest canopy volume. In the high temperature experiment, the still air treated plants had the highest canopy volume, total leaf area, leaf dry weight, shoot/root ratio, leaf weight ratio and leaf area duration while the moving air treated plants had the highest root weight ratio. The 5-cnbar treatment had the highest canopy volume and biomass accumulations. The 30-cnbar treatment had the highest root weight ratio.

Estimation of the biomass production of Artemia with regard to its use in aquaculture: Temperature and strain effects

Secondary productivity was estimated for one sexual species of the brine shrimp Artemia (Artemia tunisiana) and for two inland and two coastal parthenogenetic diploid and polyploid strains ( Artemia parthenogenetica), reared in semi-intensive cultures under different natural temperature conditions. Standing biomass and productivity were affected by temperature conditions, mode of reproduction, ploidy level and habitat temperature characteristics. At high temperatures (24–30 °C), diploid and polyploid parthenogenetic Artemia strains attained the highest biomass values and productivity of the coastal parthenogenetic diploid strain was 13 times higher than that of polyploids. Differences between the inland and coastal parthenogenetic diploid strains studied may be due to genetic adaptation to habitat temperature conditions. At low temperatures (under 15 °C) only the sexual species survived, and its production values were ten times lower than those of polyploid strains during spring and summer. Productivity was directly related to standing biomass and inversely related to individual biomass. On the basis of these results, an empirical model to predict Artemia productivity from biomass and individual dry weight data is proposed. This study provides useful information for the selection of the most suitable non Artemia franciscana strains to introduce in salterns from the Old World with a given temperature regime and it also supplies practical guidelines for the easy determination of Artemia productivity.

Biochemical Analysis of Developing Wheat Grains

AbstractDeveloping wheat grain was analysed for its fresh and dry weights, water content and some enzymes of the respiratory pathway. Grain dry weight data was fitted to a polynomial equation and biphasic linear regression analysis. Based on biphasic regression analysis and data of water content, the entire wheat grain development is divided into four phases: (i) cell division; (ii) cell elongation; (iii) dry matter accumulation; and (iv) maturation. Various enzymes of glycolysis, Oxidative pentose phosphate pathway and Tricarboxylic acid cycle have been estimated during entire wheat grain development, which recorded higher activities during cell elongation phase and maintained higher levels during dry matter accumulation phase. The role of these enzymes in the generation of NADPH and provision of carbon skeleton for starch and nucleic acid synthesis is discussed.

Losses in herbage and seed yields caused by subterranean clover mottle sobemovirus in grazed subterranean clover swards

Subterranean clover (Trifolium subterraneum L.) was grown in swards into which small plants infected with subterranean clover mottle sobemovirus (SCMoV) were transplanted. Initial spread was mainly to plants adjacent to infected transplants and occurred during grazing and trampling by sheep. New sites of infection subsequently formed away from the original infection sites. Spread occurred mainly in spring and its extent varied with cultivar, site and year. Final SCMoV incidence in swards ranged from 17% of plants infected by isolate MJ in cv. Karridale in 1993 to 60% by isolate P23 in cv. Dinninup in 1991. With cvv. Dinninup and Junee, in two experiments SCMoV-infection decreased yields within patches with symptoms by 11-26% (herbage) and 5-31% (seed); in one of these experiments infection decreased overall yields of herbage by 9-10% and seed by 10-31%. In an experiment with cvv. Dalkeith and Woogenellup, SCMoV-induced overall herbage yield decreases of 10-13% were recorded despite extensive virus spread to control swards; yield losseswithin affected patches were 20-28% for herbage and 19% for seed. In an experiment with cw. Karridale and Woogenellup, SCMoV-induced yield losses within patches with symptoms were 38-44% for herbage and 15-41% for seed. Decreased seed size (mean seed weight) and fewer seeds both contributed to the diminished seed yields. Estimates of the effects of different levels of SCMoV infection on herbage yields were obtained for cv. Woogenellup by plotting dry weight data from (i) individual quadrats against percent plants with symptoms within them and (ii) whole plots against percent plot infection determined by ELISA. Losses increased in proportion to the level of infection. SCMoV infection of subterranean clover pastures not only decreases the feed available but also the seed bank which, when compounded over several years, leads to pasture deterioration. Heavy grazing, reseeding the pasture with susceptible cultivars and extended growing seasons are all likely to magnify SCMoV-induced losses.

Influence of root competition on compatibility between white clover and perennial ryegrass populations during seedling establishment

AbstractPlants of a white clover population, Ac 3785, were grown in binary mixtures with perennial ryegrass cv. Talbot and the ‘coexisting’ population, Ba 10281, in boxes. Treatments imposed were ‘no root competition’ and ‘full competition’, which prevented or allowed the root systems of the competing species to intermingle respectively. Shoot competition was permitted in both treatments. Measurements of dry‐matter yield and leaf area of the clover and grasses were made on three occasions following sowing.The dry‐matter yield of both grasses was higher than that of clover at all three harvests and under both treatments, and this yield advantage tended to increase with time. Both grasses yielded more under full competition than where root competition was prevented. Talbot was higher yielding than the coexisting population under both treatments. Clover dry weight and leaf area index (LAI) were considerably higher under the ‘no root competition’ treatment. There was no effect of companion grass on clover dry weight, but clover LAI was significantly higher with its coexisting population than with Talbot in the ‘no root competition’ treatment.The LAI and dry weight data indicate that clover leaf morphology changed in response to the companion grass where root competition was prevented. Thus, the superior aerial compatibility of Ac 3785 with its coexisting grass was limited by below‐ground factors. Possible ecological reasons for this effect are discussed.

Nitrogen Rate and Timing of Nitrogen Application in Poinsettia (Euphorbia pulcherrima Willd. Ex Klotz.)

`Celebrate 2' Poinsettias were grown for 8 weeks in a controlled-environment growth room until first signs of bract coloration. In growth stage I (GSI; weeks 1 through 4) low, medium, and high N rates (25, 75, and 125 mg N/liter, respectively) were applied by subirrigation (no leaching). Following floral induction [growth stage II (GSII), weeks 5 to 8], there were nine treatments: all possible combinations of the three N rates in GSI plus three rates (75, 125, and 175 mg N/liter) in GSII. Although >80% of shoot dry weight and >90% of total leaf area developed during growth GSII, reaching an acceptable plant size by week 8 depended on receiving adequate fertilization in growth GSI. In contrast, leaf chlorosis, noted in plants receiving the lowest rate in GSI, was rapidly reversed by increasing the N rate in GSII. Quadratic regression equations fitted to shoot dry weight and leaf area data predicted that using 125 mg N/liter in both growth stages gave maximum responses at week 8. However, using 75 mg N/liter in GSI and 125 mg N/liter in GSII also produced acceptable growth in poinsettias. Our results suggest that some growth restriction imposed by N availability during the first 4 weeks of growth may be acceptable and perhaps desirable to reduce growth regulator use and the environmental impact of overfertilization.

LEAF, STEM, AND FLOWER CHARACTERISTICS OF ROSA HYBRIDA L. UNDER DIFFERENT CO2 CONCENTRATIONS

Two greenhouses received ambient CO2 and two were enriched between 1000 and 1200 ppm CO2 when vents were closed. Two-year-old Rosa hybrida L. `Royalty', `Emblem', and `Samantha' plants growing in each house were pinched 20 Oct. and 28 Dec. 1992 for Christmas and Valentine's Day crops. All temperature set points were 22C/17C day/night. At flowering, 5 shoots from each bench location were destructively sampled for stem diameter, stem length, and fresh and dry weights of stem, leaves, and flower bud.At flowering for the Christmas 1992 crop, shoots in the enriched houses tended to have larger stem, leaf, and flower fresh weights, and larger stem diameters. Analysis of variance found stem lengths of combined cultivars to be longer (p < .05) in the CO2 enriched houses. Mean stem lengths were 68.8 cm and 63.9 cm for flower stems in CO2 enriched and ambient houses, respectively. Dry weight data from the Christmas crop, and results from the 1993 Valentine's crop will be presented.

WITHIN-ROW SPACING EFFECTS ON TRAITS OF IMPORTANCE TO MECHANICAL HARVEST IN PAPRIKA PEPPER

Several within-row spacings (WRS) were tested on paprika peppers (Capsicum annuum L.) grown at a standard between-row spacing of 0.9 m. The objective was to maximize marketable yield per hectare while minimizing plant size and lodging to as to facilitate mechanical harvest. Total and marketable fruit dry weights per hectare decreased linearly as WRS increased from 5 to 25 cm in 1990. The 20 and 25 cm WRS produced undesirably massive plants with a high rate of lodging. Fruit yields were unaffected by WRS of 5, 10, and 15 cm in 1991, but lodging and stem dry weight data continued to favor the higher populations. Two experiments performed without thinning in 1992 produced WRS comparisons of about 4.5 vs. 8 cm and 7 vs. 11 cm, respectively. Stem dry weights were highest with the wider WRS, but marketable fruit dry weights per hectare and lodging percentages were unaffected by WRS in either 1992 study. A target WRS of 10 cm (about 11 plants/m2) is recommended for paprika intended for mechanical harvest. Net WRS <10 cm are preferable to those >10 cm.

Development of Soybean Fresh and Dry Weight Relationships for Real Time Model Calibration

AbstractMeasurements of dry weight and crop phenology are normally used to validate comprehensive growth models. To reduce this requirement in applications such as large area yield forecasting, the present research was conducted to study the change of dry matter concentration (ratio of dry weight to fresh weight) of the vegetative and reproductive plant components of soybean (Glycine max (L.) Merr.]. The paper evaluates the usefulness of simple statistical equations that relate dry matter concentration to developmental stages for the specific purpose of growth model calibration. During the 1984 through 1985 seasons, five cultivars of soybean were grown in five locations throughout the soybean producing regions of the U.S. Soil type, planting date, plant population, and irrigation management varied from site to site. Plant samples were taken at 1‐ to 2‐wk intervals during the growing season for fresh weight and dry weight of vegetative parts and pods, and counts of reproductive sites. In most of the field locations, dry matter concentration of different soybean parts was found to follow a predictable pattern. The pattern was explained for most locations by a simple relation of developmental stage and vegetative dry matter concentration, using data collected until the beginning of pod fill. A second model explained the course of pod dry matter concentration over developmental stage, using data collected after the beginning of seed growth. Insignificant differences among regression lines of extreme locations suggest that the course of dry matter concentration may be of an inherent nature, with minor impact due to differences of cultivar, or weather. The equations developed in this paper to estimate dry weight data will reduce the effort of calibrating and/or validating soybean comprehensive growth models by requiring only the collection of fresh weight samples at known phenological events.

Dynamics of biomass partitioning in field-grown radish varieties, treated with ethylenediurea

During the growing season of 1990, five staggered crops of radish (Raphanus sativus L.) were grown in the field, using the cultivars 'Cherry Belle', 'Red Prince', and 'Red Devil B'. Half of the plants received a soil drench (100 ml plant(-1); 100 mg litre(-1) of ethylenediurea (EDU) once, early in plant development. Destructive harvests were carried out at 2-day intervals during vegetative development. Non-linear growth kinetics, derived from Richards' function, were fitted to the dry weight data of the total plant, main organs (shoot and hypocotyl) and to the dry weight ratio between below-ground and above-ground organs. Estimating the parameters of these non-linear functions and testing their differences between EDU-treated and untreated plants unveiled biologically meaningful information on the impact of different levels of ambient ozone (O(3)) during the growth periods. The modified function which was applied to the data of biomass partitioning between the major plant parts was more powerful in detecting transient alterations in assimilate allocation compared to the growth dynamics of individual plant organs. At low levels of O(3), biomass partitioning towards the below-ground sink organs was slightly delayed and finally restricted in EDU-treated plants. When ambient O(3) reached moderate levels, which did not cause visible foliar injury, assimilate partitioning between organs was only insignificantly altered during early growth when EDU-treatments were compared. As growth progressed, however, less assimilates were allocated towards the hypocotyl and roots in the plants not protected by EDU. This pattern was similar in all cultivars tested, but was smallest in 'Cherry Belle', which is known to be sensitive to O(3) with respect to foliar injury. During the 15- to 19-day periods of rapid growth, the O(3)-exposure >80 nl litre(-1) ranged from 0.015 to 0.209 microl litre(-1) O(3) h, which corresponds to 7 h d(-1) mean values between 40 and 50 nl litre(-1) O(3), confirming that ambient ozone did not exceed a moderate level in this study.

Growth and shoot:root partitioning of spinach plants as affected by nitrogen supply

ABSTRACTSpinach plants (Spinacia oleracea L.) were grown hydroponically in fixed environmental conditions either at full nitrate availability (11·8mol m‐3) or at a suboptimum relative nitrate addition rate of 0·20d‐1, 0·15d‐1 or 0·10d‐1 respectively, the other nutrients being adequately provided. The relative growth rate (RGR) of the plants varied significantly with the nutrition treatment and decreased during development in all treatments. The concentration of reduced nitrogen in the plants grown at full nitrate availability did not change significantly during the experimental growth period and nitrate accumulation was substantial. After an adaptation period, the concentration of reduced nitrogen in the plants at the suboptimum nitrate addition rates increased during growth and was lowest at the lowest relative nitrate addition rate. Nitrate uptake was almost complete in the suboptimum treatments and nitrate accumulation was negligible as long as the concentration of reduced nitrogen was below 2·0 mmol (g dry weight)‐1. The RGR of all plants was proportional to the concentration of reduced nitrogen in the plant minus a minimal tissue concentration required for growth. However, the proportionality factor was inversely related to the plant mass. This relationship was summarized in an empirical model which explained 98·7% of the variance of the dry weight (log scale) data of all treatments at all harvests. The model was compared with other growth models found in the literature. The shoot/root weight ratio increased from 2 to 4 if nitrate provision was not limiting, and initially, this ratio decreased at suboptimum nitrate provision but increased at higher growth stages. Possible explanations of the dynamics of dry matter partitioning are discussed in relation to models.

Nitrogen-fixing potential of micropropagated clones of Acacia mangium inoculated with different Bradyrhizobium spp. strains

Five A. mangium seedlings of different shoot lengths were selected from a 600-seed screening experiment and micropropagated. Two-week-old rooted microcuttings of the 5 micropropagated clones were inoculated with 3 specific Bradyrhizobium spp. strains in 15 combinations. After 5 months of growth, nodule dry weight and shoot dry weight data showed significant effects of clone and Bradyrhizobium spp. strain. Clones RR-G1 and IR-M2 and Bradyrhizobium sp. Aust13c resulted in the highest dry-matter production and most efficient nodulation. No interaction was observed between clone and Bradyrhizobium spp. strain, which indicates that the Bradyrhizobium spp. strain and the host plant can be selected separately.

Efficacy of five different formulations of clopyralid on Cirsium arvense (L.) Scop, and Polygonum convolvulus L

Summary:Experiments were conducted in a controlled environment growth room to compare the phytotoxicity of five formulations of clopyralid and to determine the effect of post‐treatment simulated rainfall applications on the efficacy of these formulations. Clopyralid, formulated as the acid, monoethanolamine salt, potassium salt, 2‐ethylhexyl ester or 1‐decyl ester was applied to Cirsium arvense or Polygonum convolvulus at the 8–10 and 4–6 leaf stage of development, respectively.Based on the shoot and root dry weight data from both species, the 2‐ethylhexyl ester was consistently less phytotoxic than the other four formulations. With respect to Cirsium arvense shoot and root dry weight, there was no difference in efficacy between the acid, monoethanolamine salt, potassium salt and 1‐decyl ester. Root dry weight changes of Polygonum convolvulus did not correlate well with an increase in dose of the five formulations. Maximum increase in stem diameter of Polygonum convolvulus occurred after application of 100 g a.e. ha−1 of the acid, monoethanolamine salt, potassium salt and 1‐decyl ester whereas with the 2‐ethylhexyl ester, the maximum increase occurred after application of 200 g a.e. ha−1. Simulated rainfall was applied 3, 6, 9 or 12 h after application of 200 g a.e. ha−1 of the five clopyralid formulations to both species. Rainfall reduced the efficacy of clopyralid, regardless of the formulation or species. The 2‐ethylhexyl ester was less efficacious than the other four formulations, irrespective of the timing of simulated rainfall.

Growth, Photosynthesis, and Chlorophyll Concentrations of Red Spruce Seedlings Treated with Mist Containing Hydrogen Peroxide

AbstractThe effects of controlled exposures of mist (50–90 µm drop size) containing hydrogen peroxide (H2O2) on greenhouse‐grown red spruce (Picea rubens Sarg.) were studied for 16 wk coincident with the 1987 growing season. One‐year‐old seedlings were treated with simulated mist containing 0, 15, 59, or 235 µM H2O2 three times each week from 2400 to 0930 h. Height, diameter, net photosynthesis, respiration, chlorophyll, and dry weight measurements were made. After 16 wk of H2O2 exposures, no visible symptoms of foliar injury were evident. Similarly, no differences in net photosynthesis, respiration, or needle pigment concentrations were observed. Analysis of covariance of the dry weight data showed significantly greater dry matter in seedlings exposed to 235 µM H2O2 treatment vs. those treatments representing a range of ambient conditions (0, 15, and 59 µM). Mean relative growth rates were also the greatest for seedlings of the 235 µM treatment. Given these controlled exposure studies, it is hypothesized that concentrations of wet‐deposited H2O2 of up to twice current ambient maximums are unlikely to reduce red spruce seedling growth through direct impairment of leaf function.

The Response of Four Sorghum Accessions/Cultivars to Salinity During Plant Development

AbstractWhole‐plant‐response of four sorghum accessions to increasing mM NaCl concentrations of 0, 100, and 150 was assessed at three growth stages (GS‐1, GS‐2, and GS‐3), in a sand‐culture experiment. Accession comparisons were made on the basis of absolute and relative salt tolerance values. Increasing salinity significantly reduced plant height at GS‐1, whilst shoot and root dry weight were less affected. The effect of NaCl on these characters was greater at GS‐2 and GS‐3, and accessions differed significantly in their responses to salinity. On the basis of plant height data, Giza 114 had the highest absolute salt tolerance at all three growth stages. However based on shoot and root dry weight data, Double TX and Giza 114 were both significantly more NaCl‐tolerant than INRA 133 and INRA 353 at GS‐2. Based on relative salt tolerance values of shoot and root dry weight, and plant height, Double TX and Giza 114 were more affected by salinity at GS‐3 than INRA 133 and INRA 353. INRA 133 and INRA 353 exhibited progressively higher tolerance at all growth stages, and produced more grains than Double TX and Giza 114, and consequently had higher grain yield per plant. NaCl salinity had little effect on grain weight. Plant sensitivity to NaCl at three growth stages differs in the four accessions, and is genotype‐specific. This suggests that there is considerable variation in salt tolerance in sorghum at the adult stage which may be exploited through selection and breeding of plants to effect further improvement in salinity tolerance in this species.

Growth dynamics and water use of seedlings of Quercus alba L. in CO2 -enriched atmospheres.

White oak (Quercus alba L.) seedlings were grown from a half-sib collection of acorns in pots containing a nutrient-Poor forest soil and maintained in controlled-environment chambers having mean atmospheric CO2 concentrations of 389, 496, and 793 cm3 m-3 . Additions of nitrogen and phosphorus to the soil increased plant growth, indicating that the unfertilized plants were nutrient deficient. Despite the nutrient deficiency, the plants grown in elevated concentrations of CO., generally were larger than those in ambient CO2 , but dry weight data from harvests at 5, 12, 24, and 36 weeks provided insufficient evidence of an effect of CO2 because of the high variability associated with the recurrently-Hushing habit of these seedlings. Mathematical growth analysis based on periodic non-destructive measurements allowed comparisons of the continuous growth patterns of the plants and avoided the problems of ontogenetic variation. CO2 , enrichment was thus shown to increase plant growth rate primarily through increased unit leaf rate rather than increased leaf area production. Unit leaf rate during the second half of the experiment was 22 and 27% higher in the medium and high concentrations of CO2 compared with that in low CO 2 instantaneous measurements of foliar gas exchange also showed that CO2 , assimilation increased with CO2 , enrichment. The most pronounced effect of CO2 , enrichment was increased water-use efficiency, which was shown both through whole-plant gravimetric analysis and instantaneous gas exchange measurements. Whole-plant water-use efficiency for the duration of the experiment was increased by 52 and 82% by the mdium and high concentrations of CO2 . Limitations of resources, including water and nutrients, do not preclude plant growth responses to CO2 enrichment of the atmosphere.

Vascular flow resistance in rabbit hearts: “Apparent viscosity” of RBC suspensions

Isovolumically beating, isolated hearts from male New Zealand rabbits were perfused retrograde via the aorta at a paced rate of 180 to 200 beats per minute. Perfusions were effected at arterial pressures (AP) ranging from 10 to 80 mm Hg. Perfusions (Krebs-Henseleit buffer + 1% BSA + insulin, 100 μl/liter; same + 40% sheep RBC; same + 40% bovine RBC) were dosed with 15 m M papaverine to induce maximum vasodilation. In each case normalized flow rate (per unit heart mass) varied linearly with AP but all linear regressions extrapolated to a positive, zero-flow value of AP. Normalized flow resistance, defined as the slope of the line fitted to the pressure-drop vs normalized flow (per unit of dry heart weight) data, was not affected by the change from sheep to bovine RBC in the maximally dilated hearts. Data from RBC-free perfusions were inserted in Poiseuille's law to compute an effective geometric factor for the organ vasculature. This is turn was used to calculate apparent viscosities of the RBC suspensions. These were indistinguishable for the different RBC suspensions and fell between 0.5 and 0.6 of the respective high shear-rate values measured in a cone-plate viscometer, thus agreeing with the findings of S.R.F. Whittaker and F. R. Winton (1933, J. Physiol. (London), 78, 339–369) for the dog hindlimb. Relative apparent viscosities (suspension viscosity ÷ suspending medium viscosity) were 1.89 (sheep RBC) and 1.85 (bovine RBC) and are in good agreement with the range deduced for the mesenteric microcirculation of the cat from the microscopic measurements of Lipowsky et al. (1980), signifying that the low apparent in vivo viscosity determined for an intact organ follows from the microhematocrit deficiency.

Experimental Decomposition of Litter from the Tamaulipan Cloud Forest: A Comparison of Four Simple Models

Four differential equation decomposition models were postulated, based on different assumptions of the behavior of the decomposition rate (. : Model 1, rate constant; Model 2, rate decreasing linearly as a function of the remaining litter fraction; Model 3, rate decreasing nonlinearly as a function of the remaining litter fraction; and Model 4, litter formed by two fractions, each having a constant decomposition rate but varying in proportion with time (thus the overall rate will also vary with time). The models were tested against dry-weight data from three contrasting litter types from the Tamaulipan cloud forest: leaves of Liquidambar styraciflua, fruits of Prunus serotina, and branch segments of L. styraciflua. Al three types were incubated in litter bags at constant temperature (30?C) and 100 percent relative humidity. Subsets of four replicates were collected, dry-weighed, and discarded at increasing intervals for three months. Model 1 (the negative exponential) consistently gave the worst fit to the data. The best fits were obtained from Models 3 and 4, showing the high intrinsic heterogeneity of litter and, consequently, the variability of the relative decomposition rates.

Cardenolide content and thin-layer chromatography profiles of monarch butterflies,danaus plexippus L., and their larval host-plant milkweed,asclepias viridis walt., in northwestern louisiana

This paper is the first in a series on cardenolide fingerprinting of monarch butterflies and their host-plant milkweeds in the eastern United States. Spectrophotometric determinations of the gross cardenolide content of 60Asclepias viridis plants in northwestern Louisiana indicate a positively skewed variation ranging from 95 to 432 υg/0.1 g dry weight with a mean of 245 υg/0.1 g. Butterflies reared individually on these plants contained a normal cardenolide distribution ranging from 73 to 591 υg/0.1 g dry weight with a mean of 337 υg/0.1 g. The uptake of cardenolide by the butterflies best fit a logarithmic function of the plant concentration. Female monarchs (385 υg/0.l g) contained significantly greater mean cardenolide concentrations than did males (287 υg/0.1 g). No indications of a metabolic cost for either cardenolide ingestion or storage were adduced from size or dry weight data. Thin-layer chromatograms of 24 individual plant-butterfly pairs developed in two solvent systems resolved 21 individual spots in the plants and 15 in the butterflies.A. viridis plants appear to contain several relatively nonpolar cardenolides of the calotropagenin series which are metabolized to the more polar 3'-hydroxy derivatives calactin and calotropin as well as to calotropagenin in the butterflies. The epoxy cardenolides labriformin and labriformidin were absent, although desglucosyrioside (a 3'-hydroxy derivative) appeared present in both plants and butterflies. Quantitative evaluation of theR f values, spot intensities, and probabilities of occurrence in the chloroform-methanol-formamide TLC system produced a cardenolide fingerprint clearly distinct from those previously established for monarchs reared on otherAsclepias species, supporting the use of fingerprints to make ecological predictions concerning larval host-plant utilization.A. viridis is the predominant early spring milkweed throughout most of the south central United States and may be important in providing chemical protection to spring and early summer generation monarchs in the eastern United States.