Leaf Relative Growth Rate Research Articles

Field Measurements of Photosynthesis and Leaf Growth Rates of Three Alpine Plant Species

Leaf photosynthetic measurements using a portable 14CO2 field system were carried out and leaf relative growth rates, Rl, were determined at different leaf positions of three alpine plant species throughout the growing season. Initially there was a period of high RI associated with a period of high or increasing photosynthetic activity. Following this stage was a long period of no net change in length of the living leaf with photosynthetic activity eventually exhibiting a steady decrease. The final ontogenetic stage was a period of negative Rs denoting leaf senescence which was associated with a marked decline in leaf CO2 uptake. Ontogenetic timing of these alpine species is geared with the surge and decline of individual leaf photosynthetic activity so that one to several leaves operating at near maximal photosynthetic capacity for existing conditions are always maintained during the growing season for each plant.

Effect of Light Intensity on Growth of Natural Populations of Dactylis glomerata L.

The growth of two natural populations of cocksfoot from contrasting climatic regions, Norway and Portugal, was studied in two photoperiods at three temperatures with three levels of light energy (48, 144, and 240 W m−2 in the wavelength interval 400–700 nm). There was a consistent increase in relative growth-rate (RGR) in response to increased light energy up to 144 W m−2, but above this energy level there was either no change, or, in some treatments, a decline. Net assimilation rate (NAR) increased, whilst leaf area ratio decreased from the lowest to the highest energy level in most treatments. The decrease of LAR with increased light energy could be attributed to a decrease of both leaf weight ratio (LWR) and specific leaf area (SLA), a greater proportion of dry matter being distributed to plant parts other than leaf. This effect occurred although there was a positive relationship between light energy and relative leaf growth-rate (RLGR). Population differences in these growth attributes were most marked in the treatments with low-temperature and short-day conditions. The efficiency of energy conversion of visible radiation declined from 3–4 per cent at the lowest energy level to 1–2 per cent at the highest energy level.

SOME DIFFERENCES BETWEEN SOYBEAN CULTIVARS OBSERVED BY GROWTH ANALYSIS

Spaced plants of soybean (Glycine max (L.) Merrill) cultivars were subjected to classical growth analysis. Varietal differences in mean net assimilation rate (NAR), relative growth rate (RGR), relative leaf growth rate (RLGR), leaf area ratio (LAR), specific leaf weight (SLW), and shoot/root ratio (S/R) were detected within a group of 21 cultivars grown in three tests over 3 years. Only LAR and SLW differed within another group of 23 cultivars grown in 2 years. Comparisons of cultivars with their parents showed that selection for yield had resulted in increased NAR and SLW, and in decreased LAR, S/R, plant weight, and leaf area. Many of the cultivars were transgressive segregants for higher NAR and SLW and for lower LAR. Phenotypic correlations showed that NAR was highly correlated with SLW and inversely correlated with LAR. SLW might be a useful character for indirect selection of soybean yield.

Growth analysis in relation to sowing dates in four varieties of wheat: a functional approach

Effect of three different sowing dates on growth of four varieties of wheat was analyzed using functional techniques. Crop growth rate (CGR), relative leaf growth rate (RLGR) and specific leaf area (SLA) were higher in the early sown plants compared to late sown plants. Net assimilation rate (NAR) in all the varieties increased slowly at the early stages of growth while it increased sharply at the later stages with fluctuations in most cases. The declining tendency was found in SLA at the middle stage of growth except variety C 306. Higher values of CGR were found in the early sown Protiva, leaf weight ratio (LWR) in the late sown C 306 and early sown Opata, RLGR in the early sown Opata and C 306, SLA in the late sown Opata and Protiva and NAR in all the four varieties when they were sown late. Key words: Wheat; sowing date; growth; functional technique DOI: 10.3329/jles.v2i2.7492 J. Life Earth Sci., Vol. 2(2) 17-25, 2007

Comparison of Dry Matter Production in Forage Grass Species

Dry matter production was compared between the two groups of four grass species which differ in photosynthetic capacity and optimum temperature for growth. The species were oats, Avena sativa L. Italian rye grass, Lolium multiflorum, (species of low photosynthetic capacity and low optimum temparature), barnyard grass, Panicum Crus-galli var. echinata and sorgo, Sorghum vulgare (species of high photosynthetic capacity and high optimum temperature). Experiments were carried out from summer to autumn in 1966 for 74 days with two sowing densities and for spring in 1967 for 51 days with one sowing density. The results of high density plot only were described. Panicum and Sorghum produced much higher dry matter and had higher crop growth rate (CGR) then Avena and Lolium (Fig. 1 and 4) in the experiment in 1966. It was shown that the former species had the higher leaf area indeces (LAI) in an early growth stage (Fig. 2) and had the higher net assimilation rate (NAR) even in the growth stage of high LAI than the latter species (Fig. 3). The comparison was also made in dry weight ratio of nonphotosynthetic system to photosynthetic system and specific leaf area, but no consistent result with dry matter production was obtained (Table 3). In the experiment in 1967, which was carried out for a period of lower temperature, longer day length and for younger stage, than the one of 1966, sorghum showed higher CGR, higher relative growth rate, higher relative leaf growth rate and higher NAR than Lolium (Table 5). It was noticed that NAR was one of the most important factor for dry matter production in the young stage with low LAI. From these results, the significance of NAR or photosynthetic capacity per unit leaf area (P) in dry matter production was discussed. It was concluded that not only leaf area but NAR or P were important and that the high dry matter production of forage grasses could be achieved with the species which possess both the ability of high NAR or P and of high growth rate in leaf area simultaneously.

ANALYSIS OF THE GROWTH OF SOYBEANS AS AFFECTED BY PLANT POPULATION AND FERTILIZER

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.

Plant Growth in Polyethylene Glycol Solutions in Relation to the Osmotic Potential of the Root Medium and the Leaf Water Balance

The changes in leaf extension, plant dry weight, leaf area, net assimilation rate (E), relative growth-rate and relative leaf growth-rate (R£), have been studied for four species grown for 2 weeks in solutions of polyethylene glycol 4000 of controlled osmotic potentials. All aspects of growth were decreased by decreasing the osmotic potential (■sol) °f the root medium and the leaf water potential ( p from the values in the control plants decreased growth during the first week but partial recovery was apparent during the second week's growth in solution culture, when leaf extension, E, Ri, and Riiincreased in plants subjected to stress. Examination of the water balance, water potential, osmotic potential, and turgor of the leaf in relation to relative water content suggests that recovery was related to increased turgor and that the ability of the plants to grow at reduced values of the osmotic potential of the root medium and of the leaf water potential depended on the maintenance of turgor.

Comparative studies of upland and swamp rice varieties (Oryza sativaL. ). I. Effect of soil moisture on growth and nutrient uptake

SummaryGrowth and nutrient uptake by an upland rice variety, Agbede and a swamp rice variety, BG 79, were studied under four different soil moisture regimes (60, 80, 100% soil moisture saturation and flooding).BG 79 (Swamp rice) ultimately attained greater mean total dry weight than Agbede (Upland rice), except in the flooding treatment, where the reverse applied. For both, 100% soil moisture saturation gave the greatest total dry weight increase, whereas the driest soil depressed dry-matter production: plants grown on soil maintained at 80% moisture saturation ultimately attained greater mean total dry weight than those grown on flooded soil. Flooded plants of the swamp rice outyielded plants grown on soil maintained at 80% moisture saturation, but the reverse applied to the upland rice.Total leaf numbers were usually greater in BG 79 than in Agbede during the tillering and mid-vegetative stages. Increase in the soil moisture up to complete saturation increased the total leaf number in both varieties.Mean leaf area was greater in Agbede than in BG 79 during the tillering and midvegetative stages. During these two periods of growth the 100% saturation treatment produced plants with the greatest leaf area, whereas 60% soil moisture saturation produced plants with the smallest leaf area in both varieties.BG 79 had more shoots than Agbede. During tillering saturated and flooded soil encouraged the production of shoots in both varieties, but the driest soil prolonged the tillering period, especially in BG 79. Final shoot number tended to decrease with decreasing soil moisture. The percentage shoot mortality in Agbede was not significantly affected by soil moisture regimes, but BG 79 plants grown on the driest and saturated soil had significantly greater percentages of shoot mortality than flooded plants. In both varieties, plants grown on the driest soil had significantly greater percentage shoot mortality than those grown on soil maintained at 80% moisture saturation.Mean Relative Leaf Growth Rate and Net Assimilation Rate were significantly faster in BG 79 than in Agbede variety, but the reverse applied with regard to Leaf Weight Ratio.In both varieties flooded plants had the lowest concentration of manganese, especially during tillering. The small adsorption of Mn with flooding is attributed to a probable antagonism between iron and manganese.

Studies of the Physiological Basis for Yield Differences. II. Variations in Dry Matter Distribution Among Aerial Organs for Several Dry Bean Varieties1

The extent of variation in distribution of accumulated dry matter among aerial organs at maturity was compared for 11 varieties of Phaseolus vulgaris L., representing marrow, red kidney, yelloweye, and pea types of dry bean. The lowest percentages of aerial dry weight present as fruit (seed and pod wall) were exhibited by the red kidney and pea bean varieties. ‘Charlottetown’ yelloweye exhibited the highest percentage as fruit and the highest harvest index (percentage of aerial dry weight as seed), but it had the lowest seed yield because of early maturity and accompanying low dry matter accumulation. The second highest harvest index was exhibited by ‘Cornell 7–16’ which regularly out‐yielded all other varieties. Harvest indices of the varieties varied from 53% to 67%. The high seed yield and harvest index of 7–16 were accompanied by the highest ratio for seed weight divided by pod wall weight. Harvest index was not correlated with time to maturity nor with determinate and indeterminate growth habits. In addition to harvest indices the varietal expressions of leaf‐area, leaf‐area ratio, relative growth rate, relative leaf growth rate, and net assimilation rate are discussed. This information on genetic variability and the inter‐relationships of these many factors provides improved understanding of the physiology of yield differences in beans. It also provides a physiological basis for formulating a program of breeding higher yielding dry bean varieties.

The Use of a Mathematical Model for the Analysis of Manurial and Weather Effects on the Growth of Carrots

A model for the study of yearly and other variation in crop yields, based on a generalized form of the logistic equation of growth, was applied to three years' growth analysis data on carrot crops from 16 plots of a long-term manurial experiment. In the ideal case, it is postulated that the growth in different years of carrot leaves or taproots on soil receiving a given manurial treatment could be described by a single curve if time in days was replaced by a scale based on one or more meteorological elements which affect relative growth-rates. The equation fitted the data on the growth of the leaves but not that on the taproots. For leaf growth, the use of the sums of solar radiation, day degrees or evaporation from an open water surface did not give curves that fitted the growth data better than those obtained with time in days. Yearly differences in leaf (but not taproot) growth appeared to be related to corresponding differences in rainfall amounts, and it is suggested that a scale taking account of soil moisture tension might have given a better fit to the model. It appeared that whereas the relative leaf growth-rate was a function of leaf but not taproot weight, relative taproot growth-rate was a function of taproot weight and leaf weight. A further model for the growth of carrots, based on this hypothesis is described.

Relationship of Relative Leaf Growth Rate to Net Assimilation Rate and its Relevance to the Physiological Analysis of Plant Yield

IN the growing plant, where the photosynthetic tissues make the major contribution to dry-matter production, the absolute growth rate at any time is the product of the rate of increase in weight per unit of leaf (net assimilation rate1, N.A.R.) and the amount of leaf present. The latter is usually expressed in terms of leaf area, which is the product of leaf weight and the area-to-weight ratio.

PLANT GROWTH AND THE AERIAL ENVIRONMENT

SummaryA detailed description is given of the growth of Impatiens parviflora DC in the laboratory at 15° C and saturation deficits of 1.5 or 2.0 mm Hg, illuminated for a 16‐hour day with light quantities of 11.2, 13.8, 20.6 and 26.2 cal./cm2/day. Growth under these conditions is compared with growth under artificial shades in the field, described in paper I of this series. The description and comparison cover growth in dry weight and leaf area, relative growth rate and relative leaf growth rate, unit leaf rate and leaf‐area ratio, specific leaf area, the distribution of dry matter between leaf, stem and root, and the dry weight/fresh weight ratios of leaf, stem and root. In all these account is taken of ontogenetic drifts up to dry weight of 500–600 mg (reached at an age of about 6 weeks) above which analysis is complicated by self‐shading.Nearly all the comparisons reveal closely similar plants, passing through similar ontogenetic drifts, and make it possible to use the laboratory studies, which in general reveal relationship with greater detail and precision, to help to interpret growth in the field.Observations are included on the effects of transferring plants from the lowest to the highest light and vice versa. The complications which this causes in the calculation of unit leaf rate are discussed. When they have been overcome it is shown that plants transferred to a given intensity have a unit leaf rate almost identical with that of plants grown in this intensity, differences in growth being due to differences in leaf‐area ratio (mainly reflecting differences in specific leaf area). In other respects adaption to a new light climate is largely complete within a week. The leaf growth of adapted and transferred plants is in harmony with the hypothesis that leaf expansion is controlled by a balance between extension due to water uptake by cells with high osmotic pressure and loss of cell wall plasticity by growth in wall thickness.Both field and cabinet observations yield a similar relationship between specific leaf area and unit leaf rate. It is shown that this relationship accounts for the relatively slight changes in relative growth rate with changing light at medium intensities. A comparison is also made of unit leaf rates in the field and in the cabinets, for equal mean daily quantities of visible radiation expressed in absolute units, problems of such measurements having been discussed. While closely similar at very low intensities, the curves rapidly diverge at higher intensities, unit leaf rate around 3.3 mg/cm2/week being reached at 26 cal./cm2/day in the cabinets and 51 cal./cm2/day in the field. Finally, the efficiency of conversion of visible radiation is shown to be about 15% for the lowest intensity in the cabinets, falling to 12.5% at the highest, and 3% in full daylight.

EFFECTS OF NUTRITION AND LIGHT INTENSITY ON SYMPTOMS OF LEAF‐ROLL VIRUS INFECTION IN THE POTATO PLANT*

Increased nitrogen supply to potato plants infected with leaf‐roll virus greatly reduced the intensity of leaf symptoms, and caused a smaller and less consistent reduction in phloem necrosis. Application of phosphatic fertilizer initially reduced leaf symptoms, but later increased them; it increased phloem necrosis at all stages of growth. Potash slightly intensified leaf symptoms, but not phloem necrosis. Shading, which approximately halved the light intensity, reduced leaf symptoms but had no effect on phloem necrosis.The masking of leaf symptoms by nitrogen, and by phosphorus in the early stages of growth, was closely correlated with increases in relative leaf growth rate produced by these nutrients.Leaf rolling and phloem necrosis are considered to be independent symptoms not causally related, because they were differentially affected by nutrient supply and shading, and each could occur without the other.

THE EFFECT OF TIME OF APPLICATION OF NITROGENOUS FERTILIZER ON POWDERY MILDEW OF WINTER WHEAT

Applying nitrogenous fertilizer (N) to wheat plants of different ages affected the incidence of powdery mildew, Erysiphe graminis DC, differently. When N was applied before the flag leaf had emerged, the infection‐index (number of pustules per 100 sq.cm. of leaf blade) increased to a maximum and then declined. If N was applied after the flag leaf had emerged, the infection‐index increased steadily without reaching a peak, and the increased susceptibility was not associated with an increased relative leaf growth rate as when N was applied earlier.The integral of the number of pustules per unit area with time, and the number of perithecia on the leaves of the main stem, both increased with increasing delay in the application of N. Plants given N in either April or May had at least three times as many pustules as those given N in January. The time when N was applied did not affect the date when perithecia appeared.After adding N to nitrogen‐deficient plants, the already mature leaves which had resisted mildew infection, became susceptible. This change is not associated with changes in the epidermal wall.

A study in soil cultivation. The effects of varying soil consolidation on growth and development of rain-grown cotton

1. Experiments were carried out in four seasons at Barberton, South Africa, occupying approximately 2¼ acres of ground. Three soil treatments were used, viz. Normal (N), Compressed (C) and Grubbed (loosened) (G).2. Measures of consolidation of the soil were made with a specially designed apparatus, and large differences established (pp. 516–520).3. Estimations of water content and nitrate content were carried out. No great differences were found (pp. 520–524).4. Fortnightly samples of the plants were taken, from which numerical data were collected designed to estimate morphological development (primary data, pp. 526–529).5. Derived data on net assimilation rate, relative leaf-growth rate and efficiency index were calculated (pp. 529–533).6. Growth in total dry weight was found to conform approximately with an exponential law up to the time of flowering. Up to this stage also net assimilation rate was found to remain constant.7. Growth differences between treatments were related to variation in net assimilation rate only (p. 531).8. The results were analysed statistically. Significant results alone are emphasized.9. In all respects growth and development on the consolidated soil was more rapid than that on the grubbed soil, normal being generally intermediate.10. The results are discussed with reference to the question of nitrogen supply, water supply and aeration of the soil.