Relative Leaf Area Growth Research Articles

Wheat Can Access Phosphorus From Algal Biomass as Quickly and Continuously as From Mineral Fertilizer.

Algae can efficiently take up excess nutrients from waterways, making them a valuable resource potentially capable of replacing synthesized and mined fertilizers for agriculture. The capacity of algae to fertilize crops has been quantified, but it is not known how the algae-derived nutrients become available to plants. We aimed to address this question: what are the temporal dynamics of plant growth responses to algal biomass? to better propose mechanisms by which plants acquire nutrients from algal biomass and thereby study and promote those processes in future agricultural applications. Data from various sources were transformed and used to reconstruct the nutrient release from the algae Chlorella vulgaris and subsequent uptake by wheat (Triticum aestivum L.) (as reported in Schreiber et al., 2018). Plants had received 0.1x or 1x dried algae or wet algae, or zero, 0.1x or 1x mineral fertilizer calculated from agricultural practices for P application and grown to 55 days in three soils. Contents of P and other nutrients acquired from algae were as high as from mineral fertilizer, but varied based on moisture content and amount of algae applied to soils (by 55 days after sowing plants with 1x mineral fertilizer and 1x dried algae had 5.6 mg P g DWshoot; 2.2-fold more than those with 0 or 0.1x mineral fertilizer, 0.1x dried algae and wet algae, and 1x wet algae). Absolute and relative leaf area growth and estimated P uptake rates showed similar dynamics, indicating that wheat acquires P from algae quickly. A model proposes that algal fertilizer promotes wheat growth after rapid transformation in soil to inorganic nutrients. We conclude theoretically that phosphorus from algal biomass is available to wheat seedlings upon its application and is released gradually over time with minor differences related to moisture content on application. The growth and P uptake kinetics hint at nutrient forms, including N, and biomass stimulation worthy of research to further exploit algae in sustainable agriculture practices. Temporal resolved phenotype analyses in combination with a mass-balance approach is helpful for understanding resource uptake from recycled and biofertilizer sources by plants.

Melon crops (Cucumis melo L., cv. Tendral) grown in a mediterranean environment under saline–sodic conditions: Part II. Growth analysis

Abstract An irrigation experiment using saline–sodic waters was carried out in 2004 in the Volturno river plain (southern Italy) to investigate the growth of the melon cultivar Tendral under saline–sodic conditions. Four salinity irrigation treatments (C, T0.5, T1 and T2) were tested using water with electrical conductivities of 0.9, 8.7, 15.3 and 28.2 dS m−1, respectively. At the end of the crop cycle the electrical conductivity ( E C e d ) of the saturated paste in the soil profile between 0.0 and 0.9 m reached values of 0.9, 3.2 4.2 and 6.6 dS m−1, respectively, for the C, T0.5, T1 and T2 treatments. Increasing salinity led to a rise in specific leaf area (SLA; cm2 g−1) while it reduced leaf area (LA, m2 per plant), leaf area ratio (LAR, cm2 g−1), the unit leaf rate (ULR, g m−2 per day) and water use efficiency (WUE g kg−1). The relative growth rate (RGR, g g−1 per day) and the biomass produced (W, g plant−1) decreased. The reduction in RGR was closely related to the reduction in relative leaf area growth rate (RLAGR, cm2 of leaf cm−2 per day), the relative leaf weight growth rate (RLWGR, g of leaf g−1 per day) and the relative fruit weight growth rate (RFWGR, g of fruit g−1 per day). A highly significant positive correlation was found between RGR and LAR (R2 = 0.9847***), while between RGR and ULR the determination coefficient was also significant but lower (R2 = 0.6808***). The most visible effect of the salinity treatment was on LA reduction. In T0.5, T1 and T2 the LA was respectively 10%, 34% and 45% less than in the C treatment. W and the crop evapotranspiration (ETc) also decreased with increasing salinity. The reduction in W for T0.5, T1 and T2 (respectively, 2%, 28% and 40% less than treatment C) was greater than the reduction in ETc (respectively, 2%, 22% and 32% less than treatment C). Therefore also the WUE significantly decreased as salinity increased. The Tendral cv. responded to salinity mainly with morphological adaptations, first with a LA reduction that was followed by decreases in the W and ETc. There may well also be functional adaptations associated with ULR reduction.

Breaking Seed Dormancy: Revisiting Heat-treatment Duration on Germination and Subsequent Seedling Growth of Oil Palm (EIaeis guineensis Jacq.) Progenies

The role of duration of various varying heat-treatment durations on the germination of oil palm seeds is well documented. We investigated the effects of different heat-treatment durations on germination and seedling growth of 10 oil palm progenies. Batches of 250 oil palm seeds from each progeny were heat-treated at a temperature of 39° C ± 1° C for 60, 80, 100 and 120 days, to break dormancy. Seedling growth parameters measured included rate of leaf production, leaf area and relative leaf area growth rate, rate of leaf elongation, and diameter of base of seedlings stem. Germination rates for 60, 80, 100, and 120 days combined were highest for progenies A5240 and A5221 (> 80 %) but very low (< 5%) for progenies A5228 and A5268. Progenies A5240, A5291, A5234 and A5221 were found to be the most outstanding progenies in terms of germination. Prolonged heat-treatment resulted in reduced germination and less vigorous seedling growth. Heat-treatment of 60 days gave the best seedling growth performance and seedling growth was adversely affected when heat-treatment exceeded 100 days. The study indicated that heat-treatment duration of 60 days and not 80 days was effective for breaking dormancy of the oil palm seeds and successful seedling growth. This study shows that oil palm seeds germination can be obtained successfully within a short period (60 days) of heat-treatment compared to the current 80 days application by PAMOL Plantation Ltd. Lobe estate. These results could provide significant solutions to the numerous demands of oil palm seeds by local farmers.

Strategies of leaf expansion in Ficus carica under semiarid conditions

Leaf area expansion, thickness and inclination, gas exchange parameters and relative chlorophyll content were analysed in field-grown fig (Ficus carica L.) leaves over time, from emergence until after full leaf expansion (FLE). Ficus carica leaves showed a subtle change in shape during the early stages of development, and FLE was reached within ca. 30 days after emergence. Changes in leaf thickness and inclination after FLE demonstrated good adaptation to environmental conditions during summer in areas with a Mediterranean climate. Changes in gas exchange parameters and relative chlorophyll content showed that F. carica is a delayed-greening species, reaching maximum values 20 days after FLE. Correlation analysis of datasets collected during leaf expansion, confirmed dependence among structural and functional traits in F. carica. Pn was directly correlated with stomatal conductance (Gs), transpiration (E), leaf area (LA) and relative chlorophyll content up to FLE. The effect of pruning on leaf expansion, a cultural technique commonly applied in this fruit tree, was also evaluated. Although leaf development in pruned branches gave a significantly higher relative leaf area growth rate (RGR(l)) and higher LA than non-pruned branches, no significant differences were found in other morphological and physiological traits, indicating no pruning effect on leaf development. All studied morphological and physiological characteristics indicate that F. carica is well adapted to semiarid conditions. The delayed greening strategy of this species is discussed.

A generalized nonlinear tempeature response function for some growth and developmental parameters in kiwifruit (Actinidia deliciosa (A. Chev.) C. F. Liang &amp; A. R. Ferguson)

Temperature is a major factor that affects metabolic processes in living organisms. Thermal time has been widely used to account for the effects of temperature on crop growth and development. However, the thermal time approach has been criticized because it assumes a linear relationship between the rate of crop growth or development and temperature. The response of the rate of crop growth and development to temperature is nonlinear. The objective of this study was to develop a generalized nonlinear temperature response function for some growth and developmental parameters in kiwifruit (Actinidia deliciosa (A. Chev.) C. F. Liang &amp; A. R. Ferguson). The nonlinear function has three coefficients (the cardinal temperatures), which were 0ºC, 25ºC, and 40ºC. Data of temperature response of relative growth rate, relative leaf area growth, net photosynthesis rate, and leaf appearance rate in kiwifruit (female cv. Hayward) at two light levels, which are from published research, were used as independent data for evaluating the performance of the nonlinear and the thermal time functions. The results showed that the generalized nonlinear response function is better than the thermal time approach, and the temperature response of several growth and developmental parameters in kiwifruit can be described with the same response function.

べたがけに伴う温度変化とコマツナの生長との関係の簡易モデルによる解析

The effect of row cover on the growth of Komatsuna (Brassica campestris L. rapifera group) was evaluated using a simple model describing the relationship between temperature and leaf growth. The model was developed from a growth chamber experiment and shows that a) relative leaf area growth rate (RLGR) varies inversely as the 0.6th power of leaf area (LA) and b) RLGR is related to temperature by a sigmoid curve. Separate field experiments were carried out over six periods of growth and the parameters of the model were derived so as to fit the model to the results of these experiments. The growth-promoting effect of row cover was best described when the model was driven by soil temperature rather than air temperature, and it was therefore concluded that the growth-promoting effect of row cover strongly depends on its ability to warm the soil. The model-aided analysis of field-grown Komatsuna showed that leaf growth under row cover was stimulated most at lower temperatures and in the earlier growth stages. The effect of temperature was explained by the relationship between soil temperature and RLGR, in which the temperature-stimulation of RLGR decreases at higher temperatures. The effect of early growth stage was due to the enhanced rate of soil warming that results from better penetration of solar radiation to the soil surface when canopy leaf area is relatively undeveloped. Although both of these effects are already known empirically, the model-aided analysis used in the present study is able to explain them quantitatively.

Elastic and osmotic adjustments in rooted cuttings of several clones of Eucalyptus camaldulensis Dehnh. from southeastern Australia after a drought

Summary Eucalyptus camaldulensis Dehnh., considered as a drought tolerant species, was examined in relation to some mechanisms linked to drought tolerance (cell-wall elastic adjustment and osmotic adjustment) and to the intraspecific variation related to those features. Rooted cuttings of five clones obtained from three different provenances from Australia (Gilgandra: 106, 109; Lake Albacutya: 119, 125; Condamine: 105) were gradually submitted to a water limitation regime. Water stress curtailed relative leaf area growth rate, pre-dawn relative water content (RWC) and noon stomatal conductance (gs) in all clones. Shoot water parameters were estimated at the end of the drought period by pressure-volume (P–V) analysis through a repeat pressurization method. The curves obtained were analyzed by Schulte’s P–V Curve Analysis Program. Drought decreased very significantly the osmotic potential at full turgor (χπFT) and at the turgor loss point (χπTLP), with a significant clone effect: 105 had the lowest values (–2.12±0.04 MPa and –2.39±0.05 MPa). Osmotic adjustment (OA) on average was 0.34±0.02 MPa. Drought increased maximum bulk modulus of elasticity (ɛMAX) by 6.60.7 MPa. There were no clonal differences in either OA or elastic adjustment.Water stress increased significantly turgor potential at full turgor (χFT), and differences between control and stress plants show that the OA recorded did not fully account for the positive changes in turgor of stressed plants. Drought decreased shoot turgid mass/dry mass ratio (TM/DM), again with a significant clone effect: 105 had the lowest value (2.66±0.11). Reduced shoot TM/DM combined with increases in ɛMAXduring stress were indicative of cell wall adjustment, reduced turgor-loss volumes and tightening of the cell walls around the protoplasts, suggesting a cell size reduction. No effects were observed on RWC at the turgor loss point. A regression model that considered ɛMAX and χπFT explained best the response patterns of stressed plants. The mechanisms observed in Eucalyptus camaldulensis that delay growth while maintaining turgor and water uptake allow us to consider it as a dehydration postponement species.

Can simulation models help design rice cultivars that are more competitive against weeds?

Differences in competitive ability between rice cultivars IR8 and Mahsuri, grown in well-fertilised irrigated conditions, were analysed by means of a mechanistic simulation model (INTERCOM) for crop-weed interaction. The analysis revealed that the greater competitive ability of Mahsuri was due mainly to a greater relative leaf area growth rate early in the season and larger maximum plant height. Comparison of experimental results and model outcomes indicated, however, that the present model is not entirely able to quantify the trade-off between competitive and yielding ability. The extent to which traits advantageous for competition may lead to increased lodging or a larger number of unproductive tillers is not quantified by the present model. This implies that use of INTERCOM for design of more competitive rice cultivars will require continuous interaction between modelling and experimentation. With those limitations in mind, the model was used to quantify the potential contribution of various attributes to competitive ability. A sensitivity analysis demonstrated that competition for light is mainly determined by morphological characteristics of which early relative leaf area growth rate, early relative height growth rate and maximum plant height were found to be the most important. The ability of the model to identify key traits with respect to competitive ability makes it a useful tool for designing rice ideotypes.

Influence of duration of infestation by cowpea aphid (Aphididae) on growth and yield of resistant and susceptible cowpeas

The influence of duration of infestation by cowpea aphid Aphis craccivora Koch on aphid-resistant (ICV-12) and aphid-susceptible (ICV-1) cultivars of cowpea Vigna unguiculata (L.) Walp, were compared to uninfested controls. Five apterous adult aphids of similar age were infested on seedling plants for five durations of infestation: 3, 7, 14, 21 and 28 days, respectively. Treatments were removed after stipulated durations and extended leaf heights of plants (cm), counts of aphids per plant and samples for final estimates of crop growth rate (g/dm 2 land surface area/day) and relative leaf area growth rate (dm 2/dm 2/ day), were recorded. After harvest, the pods per plant and seeds per pod were recorded as plant yields. ANOVA indicated significant ( P ⩽ 0.05) interactions between cultivar and duration of infestation, and between treatment and durations, for plant yields. Extended leaf heights of ICV-1 plants were significantly reduced after 7 days duration. Aphid counts were significantly higher on ICV-1 than on ICV-12 for all durations of infestation. Compared to ICV-12 plants, pods produced by ICV-1 plants were significantly reduced at all durations, while seeds per pod were significantly reduced by infestations of 7 days or longer. Time-based action thresholds within which Aphis craccivora infestations significantly reduced the growth and yield of the susceptible ICV-1 cultivar were 7–14 days for crop growth in biomass accumulation and leaf expansion, and 3–7 days for economic yields and extended leaf heights.

Evaluation of three empirical models depicting Ambrosia artemisiifolia competition in white bean

SummaryThe performance of three empirical models describing white bean yield loss (YL) from common ragweed competition was compared using field experiments from Staffa and Woodstock, both in Ontario, Canada, in 1991 and 1992. One model was based upon both weed density and relative time of emergence. The other two models described yield loss as a function of weed leaf area relative to the crop. The model based on both weed density and relative time of emergence best described the data sets. The predicted maximum yield loss (A) and the parameter for relative time of weed emergence (C) varied across locations and years whereas the yield loss at low weed density (I) was relatively more consistent across locations and years. Use of thermal time (base temperature=10oC) rather than calendar days did not change the overall fit of the model, but reduced the value of the parameter for the relative time of weed emergence (C). The two parameter leaf area model accounting for maximum yield loss (m) gave a better fit to the data compared with the one parameter model. The relative damage coefficient (q) varied with time of leaf area assessment, location and year. Values of q calculated from relative leaf area growth rates of the crop and weed were similar to observed values.The relationship between q and accumulated thermal time was linear but varied with location and year. As management tools, models based upon relative leaf area have advantages over models based on density and relative time of emergence since the level of weed infestation needs only to be assessed once, whereas density and emergence time require frequent observations. The ability to assess accurately and quickly both the crop and weed leaf area, however, may limit the practical application of models based on leaf area. The inability of empirical models to account for year–to–year variation in environmental conditions was observed.

Dynamics of Soybean Growth in Variable Planting Patterns

AbstractReported soybean [Glycine max (L.) Merr.] yield responses to variable plant populations have been inconsistent. The varied responses are tied to the capacity of the plant stand to attain a minimal level of dry matter prior to reproductive growth. This study examined soybean growth expressed as functions of both plant and ground area to identify associations with yielding ability. Treatments consisted of high, medium, and low populations (approximately 21, 13, and 3 plants per square meter) at 0.96‐m row widths and a medium population (approximately 13 plants m−2) at 0.43‐m row widths for 2 yr. The values of total dry matter (TDM), stem DM, leaf DM, leaf area, height, and main stem node number were determined on both a whole plant and ground area basis. In addition, relative growth rate (RGR), relative leaf area growth rate (RLAGR) and net assimilation rate (NAR) were examined. Treatments with the greatest interplant space had the largest RGR, RLAGR, and NAR early in growth, thus resulting in compensation for reduced plant population. Decreases in plant DM at 91 DAP in response to increasing plant population were greater in 1988 than in 1989, and were related to poorer growing conditions in the latter year. The related TDM values were larger in 1988, with all treatments exhibiting a TDM above 500 g m−2 by early podfill (R5). In contrast, the TDM at 91 DAP of the wide row, low and medium population treatments was 300 and 426 g m−2, respectively in 1989. Seed yield differences were found in 1989 but not 1988. Differences among years and treatments concerning growth rates, plant DM, TDM, and seed yield emphasize the impact of limiting environmental factors on plant compensation in response to increased space.

Productivity‐independent initial growth of individual leaves in sunflower (Helianthus annuus L.)

AbstractGrowth rates of individual leaves attached to sunflower (Helianthus annuus) plants were measured experimentally under different levels of environmental productivity, modified by irradiance and nutrient conditions. The unfolding rate and final area of an individual leaf increased with increasing environmental productivity. The final area of an individual leaf also varied according to differences in leaf order. The declining pattern of relative leaf area growth rate (RLGR) varied with environmental productivity; leaves in a productive environment had a longer period of high sustained initial RLGR than leaves in a less productive environment. However, maximum RLGR was hardly influenced by leaf order or environmental factors such as irradiance and mineral nutrition.

Temperature adaptation of Glycine species as expressed by germination, photosynthesis, photosynthate accumulation and growth.

The temperature adaptation of five wild Glycine species of diverse geographic origin was compared with that of the cultivated species (G. max) under controlled conditions. The optimum temperature for germination was about 30°C for G. max and G. tomentella, 22°C for G. argyrea and 20°C for G. clandestina, respectively. In all the species examined, net CO2 exchange rate per unit leaf area (NCE) appeared to be maximal at growth temperatures in the range from 18/13 to 30/25°C (8 h / 16 h, 16 h daylength) with little variation over this range. Four of six species exhibited no net CO2 uptake in the light at 9/4°C after being exposed to successively lowered temperature, but G. clandestina retained a considerable net gain at this temperature. Across the species, NCE was correlated negatively with leaf size, but positively with specific leaf weight (SLW) or chlorophyll content. Most of the species revealed optimal temperatures for relative growth rate (RGR) in the range from 30/25 to 33/28°C. Across the species and growth temperatures, RGR was correlated more closely with relative leaf area growth rate (RLAGR) than with net assimilation rate (NAR). G. clandestina and G. latrobeana of cooler habitats adapted to low, temperature more strongly than other species, by increasing root/top ratio, SLW and chlorophyll content while maintaining a stable NCE. In contrast G. max tended, over a wide range of temperature, to express the greatest potential for leaf growth, leading to greater dry matter production at the expense of NCE.

Herbage Growth and Carbohydrate Metabolism of Diploid and Tetraploid Alfalfa

Polyploidy influences growth of alfalfa (Medicago sativa L.), but its impact on shoot and root carbohydrate metabolism and subsequent herbage regrowth rate remains unclear. This study related differences in herbage growth between isogenic diploid (2x) and tetraploid (4x) alfalfa populations to concentrations of root total nonstructural carbohydrates (TNC) and nonstructaral carbohydrate pools and dark respiration rates (RD) of meristematic shoot tissues. Leaf area, herbage weight, and taproots of plants were obtained weekly during 4 wk of regrowth in a controlled environment. Leaf area per plant and relative leaf area growth rate were approximately 100 and 33% greater, respectively, in the 4x population than in the 2x population. Although more herbage accumulated on 4x plants, herbage relative growth rates of populations were similar between Days 7 and 14, averaging 0.27 kg kg−1 d−1. Differences in shoot growth were not related to RD of shoot tip tissues, which averaged 55.2 ümol O2 mkg−1 s−1, or concentrations of glucose, sucrose, and starch in shoot tips. Root TNC concentrations of 2x and 4x populations were similar, initially averaging 360 g kg−1 dry wt. Concentrations of TNC increased in a linear fashion in roots of both populations during regrowth. The greater amount of shoot tissue present in the crown immediately following defoliation, along with the larger mass of individual growing shoot tips, contributed to more rapid leaf area development and faster herbage regrowth of the 4x population than the 2x population.

The influence of low soil temperature on the growth of vesicular–arbuscular mycorrhizal Fraxinuspennsylvanica

Green ash (Fraxinuspennsylvanica Marsh.) seedlings were either inoculated with Glomusetunicatum or not inoculated and grown for approximately 5 weeks under glasshouse conditions to permit root colonization with vesicular–arbuscular (V–A) mycorrhizae. Two experiments were conducted to characterize V–A mycorrhizae influence on seedling growth at low root temperature. In experiment 1, seedlings were subjected to four root zone temperatures ranging from 7.5 to 20 °C for 24 days to measure leaf area and plant height on intact seedlings. In experiment 2, seedlings were exposed to root temperatures of 12.0, 16.0, and 20.0 °C for 30 days and seedlings were destructively harvested at 6-day intervals to measure growth variables and biomass distribution. Results of experiments 1 and 2 were similar. In experiment 1, leaf area growth of mycorrhizal seedlings was significantly greater than nonmycorrhizal controls at all temperatures. Relative leaf area growth rate was greater in mycorrhizal than nonmycorrhizal seedlings at 7.5 and 11.5 °C, similar between treatments at 15.5 °C, and greater in nonmycorrhizal seedlings at 20.0 °C, differences possibly resulting from the larger size of mycorrhizal seedlings at the start of the temperature treatments. In experiment 2, temperature treatments were imposed on seedlings of the same size. Mycorrhizal seedlings had greater leaf area growth rates and relative leaf area growth rates than nonmycorrhizal seedlings at all temperatures. Phosphorus concentrations and total P content in roots and leaves did not differ significantly between mycorrhizal treatments at any temperature; however, mycorrhizal seedlings had consistently greater leaf P content than nonmycorrhizal controls. Glomusetunicatum actively stimulates green ash growth at moderately low root temperatures.

Growth and development of channel millet (Echinochloa turneriana) in relation to its potential as a crop plant and compared with other Echinochloa millets, rice and wheat

Abstract The effects of a range of temperature regimes (from 15/10 to 36/31°C), irradiances and daylenghts on the growth and development of Channel millet (Echinochloa turneriana (Domin) J.M. Black) were examined in the Canberra phytotron. The responses were compared with those of the domesticated barnyard millets (Echinochloa utilis and E. frumentacea) as well as with indica and japonica rice cultivars and with wheat. Growth and development of Channel millet can be extremely rapid, with a relative growth rate (RGR) of up to 49% per day and anthesis within 5 weeks of germination, but in these respects E. turneriana was not very different from the already domesticated species of Echinochloa, except that its flowering was less delayed by long days. CO2 exchange rates per unit leaf area (CER) and inflorescence structure were also similar, but kernel size and harvest index were greater in the cultivated millets. No compelling physiological reason was found for the domestication of Channel millet vis-a-vis other millets. The greatest difference between E. utilis and E. frumentacea was in the ability of the more temperately-adapted E. utilis to grow at cool temperatures, at which E. turneriana was intermediate. The japonica and indica rice cultivars differed in parallel with the Japanese and Indian millets. In the three millets and two rices, when grown below 21/16°C, the low RGRs were matched by low “sadpated” CER, but short tern CERs were much higher than ‘adapted’ rates at cool temperatures. At higher temperatures CER approached a plateau above 24/19°C in both rice and millet, whereas in the latter RGR increased progressively up to 36/31°C. In wheat both RGR and CER were relatively unresponsive to temperature. Across all species and temperatures, RGR was much more closely related to relative leaf area growth rate (r = 0.98) and to leaf appearance rate (r = 0.94) than to CER. It is concluded that while CER sets a limit to growth rates, the differences in RGR between species and across conditions were more closely associated with the rate of leaf expansion and the extent to which leaf appearance and expansion were limited by temperature and irradiance.

Effect of temperature and photosynthetic photon flux density on vegetative growth of kiwifruit (Actinidia chinensis)

Abstract Vegetatively-propagated female (cv. Hayward) and male (cv. Tomuri) kiwifruit plants (Actinidia chinensis Planch.) were grown from budbreak until at least the emergence of the 28th leaf in constant temperature conditions of 10, 15, 20, 25, and 30°C. At each temperature, Hayward was grown at 2 photosynthetic photon flux densities (PPFD; 280 and 650 μmol s-1 m-2), whereas Tomuri was grown only at the high photon flux density. Hayward showed a broad optimum for shoot elongation rate, leaf appearance rate, relative growth rate of the new shoot, and relative leaf area growth rate between 20 and 30°C at both high and low PPFD. All growth parameter values were considerably reduced at constant 10°C, and symptoms typical of chilling injury (including loss of chlorophyll and distorted leaf growth) were observed under the high PPFD conditions for this temperature. In contrast, for Tomuri the rates overall were generally higher and values for shoot elongation rate, leaf appearance rate, and estimated relative...

Growth relationships in silver maple seedlings fumigated with O3 and SO2

Growth analysis was used to measure the impact of low levels of ozone, alone and with sulfur dioxide, on the growth of silver maple (Acersaccharinum L.) seedlings. The seedlings were fumigated for up to 60 consecutive days with cither 0.05, 0.1, or 0.2 ppm ozone, alone and with 0.1 ppm SO2 for 12 h per day. Dry weight and leaf area development curves were calculated from data collected at 10-day intervals throughout the study. Growth analysis variables were calculated from these curves. Three variables, relative growth rate, relative leaf area growth rate, and relative leaf weight growth rate, were reduced by 0.2 ppm ozone and decreased even further when 0.1 ppm SO2 was applied. Neither the 0.05 nor 0.1 ppm ozone treatment decreased the relative growth rate of the silver maple seedlings. Even small differences in growth rate may produce large differences in dry matter accumulation over a growing season.

An analysis of the growth of silver maple and eastern cottonwood seedlings exposed to ozone

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.

Early Vegetative Growth of Cotton as Influenced by Leaf Type1

Cotton (Gossypium hirsutum L.) plants with mutant Okra (L0) and Super Okra (L5) leaves have several desirable characteristics in production systems with narrow rows and with standard rows where humidity and boll rot are high. These leaf types cause a modified fruiting expression in cotton plants. This investigation was conducted to determine the effect of the mutant leaves on rate of dry matter production, rate of leaf area development, assimilation efficiency, and dry matter partitioning during early growth of cotton plants. Three near‐isogenic lines of ‘Stoneville 7A’ (normal, Okra, and Super Okra leaves) were grown spaced field plantings during 2 years. The two mutant leaf types had significantly lower dry matter accumulation than the normal‐leaf type during both years. Values for Okra leaf‐plants were intermediate to the normal and Super Okra‐leaf plants. Initial size of cotyledons, mean net assimilation rate, and C exchange rate were similar among the leaf types and were not major factors causing the differential growth rates. The mutant types, especially Super Okra‐leaf plants, had low dry matter partitioning into leaf area. Relative leaf area growth rate of the Super Okra‐leaf plants was 12 to 20% lower than that of the normal‐leaf plants. The leaf area partition coefficient of the Super Okra‐leaf plants was 11 to 17% less than that of the normal‐leaf plants. Values for the Okra‐leaf plants were generally intermediate and frequently not significantly different from normal‐leaf plants. These factors are primarily responsible for the low growth rate of Super Okra‐leaf plants and probably to a lesser extent affect the growth of Okra‐leaf plants in a similar manner.