SOME DIFFERENCES BETWEEN SOYBEAN CULTIVARS OBSERVED BY GROWTH ANALYSIS

Smooth bromegrass (Bromus inermis Leyss.) seedlings grown in four environments were used to study effects of temperature and irradiance on seedling growth. Differences between environments, between stages of growth, and their interaction were significant for tiller number, leaf number, leaf area, specific leaf weight, shoot‐to‐root ratio, dry weight of leaf, shoot and root, and seedling dry weight. Both main effects and their interaction were highly significant for relative growth rate (RGR) and leaf area ratio (LAR), while for net assimilation rate (NAR) differences between environments were non‐significant. Seedlings grown in high light and high temperature environments produced higher dry matter than those grown in low light or low temperature. The effect of irradiance was greater than that of temperature for most characters studied. Both RGR and NAR declined gradually with advancing plant age in all environments; LAR declined only in high light environments. Simple correlation coefficients revealed that increasing RGR and LAR could be accompanied by increasing tiller number, leaf number, leaf area, seedling dry weight and shoot‐to‐root ratio. Highly significant correlations were obtained between RGR and LAR (0.69 to 0.93 at 0.001 level), whereas there was no correlation between RGR and NAR. It is apparent that variation among environments in dry matter production of bromegrass seedlings was attributed to differences in LAR rather than NAR. Specific leaf weight was negatively correlated with RGR at the 0.001 level (−0.90) and LAR (−0.97), but positively correlated with NAR at the 0.05 level (0.47).

In three experiments the growth of 16 genotypes of tomato was examined. The plants were raised in growth rooms at a day temperature of 19°C and night temperatures of 14, 10 or 6°C respectively under a light intensity of 24 Wm-2 visible radiation and a daylength of 8 hours. The results were analysed by a multivariate analysis of variance. Relative growth rate (RGR), leaf area ratio (LAR), specific leaf area (SLA) and leaf weight ratio (LWR) decreased with time. The change in net assimilation rate (NAR) was small. The decrease in RGR was mainly due to the decrease in LAR. RGR, LAR and SLA were lower and LWR slightly higher at lower night temperatures. NAR was hardly affected. The lower RGR at lower night temperatures was mainly due to a lower SLA. Significant differences between genotypes were found in total dry weight, NAR, LAR, SLA and LWR, but hardly in RGR. Significant genotype × temperature interactions occurred. LAR and SLA were positively, NAR and LAR, and NAR and SLA negatively correlated.

Potassium requirements for growth—dry matter (DM) and leaf area (LA) and related processes — relative leaf growth rate (RLGR), relative growth rate (RGR), net assimilation rate (NAR) and crop growth rate (CGR) were determined by plant analysis during the entogeny of wheat. Wheat (Triticum aestivum cv. HD 2329) plants were supplied with different amounts of K from deficient to adequate through nutrient solution. Samples were taken at specific stages for K determinations. The DM and LA were recorded at 45d, 75d and 105d. The growth related processes RGR, NAR and CGR were estimated between 30–45d, 45–75d and 75–105d. In case of RLGR the observations were carried out between 15–30d, 30–45d and 45–75d. These physiological processes and grain yield were correlated with K concentration in whole plant at 30 and 45d and top two leaves at 75 and 105d.

Net assimilation rate (NAR), relative growth rate (RGR) and relative leaf growth rate (RLGR) of soybeans [Glycine max (L.) Merrill] declined throughout the season; much of this decline and most effects of plant population on growth could be attributed to a rise in leaf area index (LAI). Increase in LAI from 0.3 to 1.0 was associated with a marked decrease in NAR. Crop growth rate (CGR) increased for the first 50 to 60 days, falling sharply thereafter. There was no optimum value of LAI.Fertilizer increased final plant weight mainly by delaying the fall in NAR and CGR. LAI was increased slightly by fertilizer application, presumably because of a higher RLGR between 50 and 70 days.The classical and regression techniques of growth analysis gave similar results, but the lower standard errors obtained with the latter revealed additional treatment effects. In some circumstances, smoothed curves used to describe growth might conceal growth fluctuations due to environmental stress.

Silver maple (Acersaccharinum L.) and eastern cottonwood (Populusdeltoides Bartr.) seedlings were treated with either 0.0, 0.1, 0.2, or 0.3 ppm ozone for 12 h/day for up to 60 consecutive days. Six seedlings were harvested from each treatment at 10-day intervals to construct growth curves for leaf area, leaf weight, and stem plus leaf weight. Relative growth parameters were calculated from these curves. Relative growth rate, relative leaf-area growth rate, and relative leaf-weight growth rate declined with an increase in time and ozone concentration. Net assimilation rate declined with time in both species. Specific leaf area and leaf-area ratio had no consistent trends.

Light with a higher red to far-red ratio (R:FR) than sunlight reduces plant growth, but the cause has not been firmly established. In the present study, cucumber seedlings were grown under normal light (similar to sunlight; R:FR = 1.4) from metal-halide lamps or high-R:FR light (R:FR = 4.3) created by transmitting their light through FR-absorbing film, and then their growth parameters and photosynthesis were compared. The relative growth rate (RGR) at high R:FR was 92% of that under normal R:FR, although the net assimilation rate (NAR) did not differ between the treatments, indicating that changes in net photosynthesis per unit leaf area did not cause the growth inhibition at high R:FR. The CO 2 exchange per unit leaf area did not differ between the treatments, which supports this hypothesis. The leaf area ratio (LAR) of total plant dry weight of high R:FR seedlings to that of normal R:FR seedlings was also 92%. This suggests that growth suppression in the high R:FR seedlings was caused mainly by decreased LAR. The specific leaf area (SLA) and leaf weight ratio (LWR), components of LAR, under high-R:FR light were 89% and 105%, respectively, of those under normal light, indicating that the smaller LAR at high R:FR mainly results from suppressed leaf enlargement per unit leaf dry matter.

Continuing use of fossil fuels in industrialized countries has created a need to understand growth responses of major crop species to elevated concentrations of CO2. An analysis was therefore undertaken of the growth of soybeans [Glycine max (L.) Merr. ‘Bragg’] grown in pots in open top field chambers at six CO2 concentrations ranging from 332 μL L‐1 (ambient) to 910 μL L‐1. Major growth response occurred with the first increments of added CO2 with a maximum 66% increase in total vegetative dry matter at the 910 μL L‐1 CO2 level. Dry weight increases were proportionate among vegetative plant parts, although the harvest index was found to decrease slightly. Greater absolute growth rates in elevated CO2 treatments were associated with greater rates of branch and internode elongation, leaf initiation, and leaf expansion. Yield increases represented greater seed numbers per plant rather than larger seeds. Percentage protein of seed decreased with CO2 enrichment. In the interval from day 5 to 2 weeks after planting, mean relative growth rate (RGR) increased asymptotically with CO2 concentration. Of the two components of RGR, the mean net assimilation rate (NAR) increased dramatically and mean leaf area ratio (LAR) decreased. In the intervals from week 2 to 7 and from week 7 to 12, RGR became constant across CO2 treatments as the positive response of NAR and the negative response of LAR became less pronounced. Both RGR and NAR fell through the vegetative growth phase at each CO2 level. The adjustment in LAR resulted from a decrease in specific leaf area while leaf weight ratio remained unaffected by CO2.

Plant height, number of leaves, diameter and fresh weight of the bulbs, and the dry weights of the component plant parts of 3 onion cvs were measured weekly, starting 40 days after transplanting, up to maturity. Red Kano had singificantly more leaves, greater leaf area, larger bulbs and fresh and dry weights than Eclipsel Bermuda and Texas Grano.Net Assimilation Rate (NAR), Relative Growth Rate (RGR), and Relative Leaf Growth Rate (RLGR) were generally high in the early stages of growth in all cvs and declined with plant age. Red Kano had much higher values than the other two. Crop Growth Rate (CGR) of tops was positive in the early stages of plant growth in all the cvs but decreased to negative values towards maturity which was due to a decrease in the dry weight of the leaf blades caused by decrease in leaf number. Red Kano and Texas Grano showed positive values throughout the experimental period. The higher CGR for the bulbs as compared to the blades was due to large quantities of carbohydrates which were translocated to the bulbs. Leaf Area Ratio (LAR) was constant in Red Kano, due to proportionate increase in leaf blade area and weight.Results of all the growth characteristics showed that Red Kano was superior to the other cvs in attaining a larger bulb size due to large number of leaves and longer growing season, resulting in the translocation of more carbohydrates to the bulbs.

Physiological and Ecological Studies in the Analysis of Plant Environment

Classical growth analysis equations were applied to three loblolly pine (Pinus taeda L.) seedling ideotypes (determined by groundline diameter) that were subjected to either 2 years of complete herbaceous weed control (low weed abundance: LWA) or no herbaceous weed control (high weed abundance: HWA). For the first 2 growing seasons, seedlings of the LWA treatment had greater mean relative growth rate (RGR) and mean net assimilation rate (NAR) values. However, during years four through five, RGR and NAR were significantly lower in the LWA treatment than in the HWA treatment. The reduction in herbaceous weed interference appeared to reduce mean leaf area ratio (LAR) throughout the study period. Several trends in this data set suggest that growth analysis parameters may be confounded with size. The largest ideotype generally exhibited the smallest RGR, and RGR declined as trees increased in biomass. To remove the potential confounding of size, the basis of comparison was changed from trees of equal age to trees of equal biomass (total aboveground dry weight at the beginning of each growing season). This method resulted in a different interpretation of the results. For a given biomass, trees in the LWA treatment had greater RGR and LAR than those in the HWA treatment throughout the study period. Growth of seedling ideotypes within a given weed abundance treatment all fell along a single curve, suggesting that there was no apparent interaction between initial seedling diameter and herbaceous weed control. After the trees reached six kg biomass, the direct benefits from reduced herbaceous interference had apparently ceased. Initially, large differences in NAR were observed between treatments, but these differences diminished as trees approached 5 kg. In contrast, differences in LAR were initially small but increased as tree biomass increased. As trees increased in biomass, the partitioning of carbon into leaf area seems to be more responsible for the productivity gains associated with weed control. For. Sci. 37(2): 655-668.

Plantas de aguapé foram cultivadas em solução nutritiva de Hoagland & Arnon n.2, cujo aumento dos níveis de N, P e Cu estabeleceu as diferenças entre os tratamentos. Utilizou-se o delineamento experimental inteiramente casualizado, com quatro repetições. As variáveis fisiológicas avaliadas foram área foliar, peso de matéria seca e taxa de crescimento absoluto, taxa de crescimento relativo, taxa assimilatória líquida, razão de área foliar, peso específico de folha, área foliar específica. Foram determinados também os teores de açúcares totais e redutores e de aminoácidos totais e a atividade das enzimas glutationa S-transferase e superóxido dismutase. Os extratos enzimáticos foram obtidos da matéria fresca da parte aérea das plantas. Após a coleta, foram determinados os pesos de material seco de raízes, pecíolos e folhas, que foram utilizados para a determinação de açúcares solúveis totais e redutores e de aminoácidos. O excesso de nitrogênio causou aumento de açúcares nas folhas e de aminoácidos nas raízes. Já o tratamento com excesso de fósforo levou ao aumento de açúcares nas raízes. Os resultados apresentados sugerem que, entre os nutrientes em excesso avaliados, o cobre (0,12 mg L-1) foi o maior indutor da atividade da GST e SOD, sugerindo que este elemento induziu estresse nas plantas de aguapé.

Abstract. Wild radish plants deprived of, and continuously supplied with solution NO−3 for 7 d following 3 weeks growth at high NO−3 supply were compared in terms of changes in dry weight, leaf area, photosynthesis and the partitioning of carbon and nitrogen (NH2‐N and NO−3‐N) among individual organs. Initial levels of NO−3‐N accounted for 25% of total plant N. Following termination of NO−3 supply, whole plant dry weight growth was not significantly reduced for 3 d, during which time plant NH2‐N concentration declined by about 25% relative to NO−3‐supplied plants, and endogenous NO−3‐N content was reduced to nearly zero. Older leaves lost NO−3 and NH2‐N, and roots and young leaves gained NH2‐N in response to N stress. Relative growth rate declined due both to decreased net assimilation rate and a decrease in leaf area ratio. A rapid increase in specific leaf weight was indicative of a greater sensitivity to N stress of leaf expansion compared to carbon gain. In response to N stress, photosynthesis per unit leaf area was more severely inhibited in older leaves, whereas weight‐based rates were equally inhibited among all leaf ages. Net photosynthesis was strongly correlated with leaf NH2‐N concentration, and the relationship was not significantly different for leaves of NO3−‐supplied compared to NO−3‐deprived plants. Simulations of the time course of NO−3 depletion for plants of various NH2‐N and NO−3 compositions and relative growth rates indicated that environmental conditions may influence the importance of NO−3 accumulation as a buffer against fluctuations in the N supply to demand ratio.

Competition, Growth Rate, and CO₂Fixation in Triazine-Susceptible and -Resistant Smooth Pigweed (<i>Amaranthus hybridus</i>)

Summary Functional traits contribute to the success of invasive plants. These traits can reflect inherent properties or they can be new adaptations from evolutionary responses to escape from natural enemies of the introduced range. We tested the hypothesis that genetic shifts in morphological and physiological traits have occurred between native and invasive populations of Sapium sebiferum. Sapium sebiferum seedlings were grown in a greenhouse using seed collected from four populations of its introduced range (US) and four from native Chinese populations that are thought to be genetic candidates of the introduced populations. We examined plant biomass production, relative growth rate (RGR), relative stem height growth rate (RHR), root : shoot ratio (RSR), total number of leaves (TLN) and leaf area (TLA), specific leaf area (SLA), leaf area ratio (LAR), net CO2 assimilation (A) and shoot specific respiration rate (RD). US populations of S. sebiferum differed from Chinese populations for most plant variables. Final shoot and total biomass, as well as, RGRs of invasive (US) populations were significantly greater than those of native (Chinese) populations, although RHR and TLN per seedling did not differ between them. Root : shoot ratios (RSR) were significantly lower, while leaf traits including TLA, LAR and SLA were generally greater for invasive populations compared to native populations. Net CO2 A was significantly higher for invasive populations than for native populations, but no significant difference in RD was found between two population types. Of 13 measured plant variables, RSRs, TLA and CO2 A were identified as traits that contributed the most to differences observed between native Chinese and invasive US populations. The suite of morphological and physiological traits functioning together may result in different growth strategies for native versus invasive populations. By virtue of these traits, invasive populations of S. sebiferum may use soil resources and light more efficiently than native populations, which may have given rise to their competitive superiority in the introduced range.

This study aims to determine the effect of drought stress and planting media combinations on the growth of soybean (Glycine max L.). The research method used was a Randomized Block Design (RBD) consisting of two factors. The first factor was planting media (P0 = 5 kg soil (control)/pot, P1 = 2 kg soil + 2 kg coconut coir (cocopeat) + 1 kg vermicompost/pot, P2 = 2 kg soil + 2 kg rice husk + 1 kg vermicompost/pot, and P3 = 2 kg soil + 1 kg coconut coir (cocopeat) + 1 kg rice husk + 1 kg vermicompost/pot). The second factor was irrigation with four methods (S0 = 100% watering, S1 = 80% watering, S2 = 60% watering, and S3 = 40% watering). The observed parameters included plant height, root length, fresh weight, leaf area, relative growth rate, and net assimilation rate. Data analysis was performed using One-Way ANOVA followed by Duncan’s test at a 5% significance level. The results showed that plant height, leaf area, dry weight, and root length under different planting media indicated that P3 had the highest values, followed by P2. The relative growth rate of soybeans under different planting media showed that P2 was the best, followed by P0, while the net assimilation rate under different planting media showed that P1 had the highest results, followed by P0. The results of plant height, leaf area, dry weight, and root length under drought stress indicated that S0 had the highest values, followed by S1. The relative growth rate of soybeans under drought stress showed that S3 was the best, followed by S2, while the net assimilation rate under drought stress showed that S1 had the highest results. The best treatment combination for plant height, leaf area, root length, and dry weight was P3S0. For relative growth rate, the best combination was P2S3, while for net assimilation rate, the best combination was P1S1. Keywords: Drought Stress, Soybean, Planting Media