Growth Parameters Leaf Research Articles

Effects of Planting Dates and Nitrogen Fertilizer Application on Growth and Yield of Contrasting Genotypes of Maize (<i>Zea Mays</i> L.)I: Leaf Growth and Its Relationship with Grain Yield

Field experiments were conducted at the University of Ilorin Teaching and Research Farm, Bolorunduro, to evaluate the effects of different levels of N application on leaf growth and its relationship with grain yield of contrasting maize genotypes planted at three planting dates. Leaf extension growth at three leaf insertions (nodes 4, 8, and12) was measured from emergence until two consecutive measurements were the same. Thereafter, leaf growth parameters including leaf extension rate, leaf extension duration and final leaf length were calculated by fitting a linear regression of leaf length against time (days after planting DAP). Leaf area index was also calculated at weekly intervals from 21 to 63 DAP. Increasing N application increased leaf extension rate (LER) in both genotypes and at all planting dates, but had no significant effect on leaf extension duration (LED). These results indicate that LER was the most important factor influencing the final leaf area production. Leaf area index was consistently higher with maize planted in May and least with those planted in June. Positive relationships were obtained between grain yield, LER and final leaf area (FLA), while LED showed inverse relationship with grain yield. These results suggested that N application increased grain yield through improved leaf area production resulting from faster LER and shorter LED. The determination of the contribution of leaf growth parameters to grain yield through regression analyses showed that the combined effects of LER, LED, and FLA made significant contribution to grain yield ranging from 33.3%with June planting to 53.4% with July planting. The results further showed that the combined effects of the leaf growth parameters were similar for both the hybrids (R2=47.5%) maize genotypes. Overall, application of 90kg N/ha gave the best leaf area production and hence the highest grain yield thereby indicating the rate to be the optimum for maize production in the study area. JARD Vol. 3 2004: pp. 83-98

TRICKLE IRRIGATION UTILIZATION FOR WHEAT IN SANDY SOIL

This study was conducted on a calcareous salt – affected soil at Ras Sudr area, South Sinai governorate during season of (2006&2007), to evaluate the influence of trickle irrigation systems (Surface and Sub-surface) on wheat crop cultivation under saline conditions of soil and water. Also, this work includes different water management technique, (quantities and discharges). The objective of the present work is to implement some of these discharges and water deficit in computing actual evapotranspiration of wheat under desert conditions, to maximize the yield production of wheat under trickle irrigation systems to save more water quantities and to keep the soil sustainable from degradation. Results of this study may be revealed that: 1- Highest yield (2254.3 kg/fed.) and growth parameters Leaf Area Index “LAI” of (85%), weight grain “W” of (61.6gm) and crude protein “P” of (15.4%) were obtained under subsurface trickle irrigation system at 100% applied water quantity and 8L/h emitter discharge . 2- Lowest actual evapotranspiration “Eta”, for (Initial, development, mid-season, late-season) growth stages and seasonal, (34, 103, 80.4, 48.1 and 265.3 mm) respectively, were obtained under subsurface trickle irrigation system at 100% applied water quantity and 8L/h emitter discharge. 3- Water use efficiency for surface and subsurface trickle irrigation systems at 80% applied water quantity and 8L/h emitter discharge was (1.17 and 2.25 kg/m3) resp.

Hormonal changes in papaya seedlings subjected to progressive water stress and re-watering

Changes on abscisic acid (ABA), jasmonic acid (JA) and indole-3-acetic acid (IAA) levels were investigated in papaya seedlings (Carica papaya L.) cv. “Baixinho de Santa Amalia” under progressive water stress and subsequent rehydration. Also, the behaviour of leaf gas exchange and leaf growth was determined under stress condition. The results indicated that ABA and JA differ in their pattern of change under water stress. ABA continuously increased in leaves and roots during the whole period of stress whereas JA showed a sharp increase and a later decrease in both organs. Re-watering reduced rapidly (24 h) leaf and root ABA to control levels whereas the influence on JA levels could not be assessed. Drought and recovery did not alter IAA levels in leaf and root tissues of papaya seedlings. In addition, water stress reduced stomatal conductance, photosynthetic rate, transpiration rate, the percentage of attached leaves and leaf growth. Rehydration reverted in few days the effects of stress on leaf growth and gas exchange parameters. Overall, the data suggest that ABA could be involved in the induction of several progressive responses such as the induction of stomatal closure and leaf abscission to reduce papaya water loss. In addition, the pattern of accumulation of JA is compatible with a triggering signal upstream ABA. The unaltered levels of IAA could suggest a certain adaptive ability of papaya to maintain active physiological processes under progressive drought stress.

Response of Resistant and Susceptible Barley to Infestations of Five Diuraphis noxia (Homoptera: Aphididae) Biotypes

Since 2003, four new biotypes of the Russian wheat aphid, Diuraphis noxia (Kurdjumov) (Homoptera: Aphididae), RWA2-RWA5, have been discovered that have the ability to damage most of the wheat germplasm resistant to the original Russian wheat aphid population (RWA1). Barley germplasm lines with resistance to RWA1 have not yet been evaluated against the newest biotypes. Our study compared how biotypes RWA1-RWA5 affected the growth and leaf damage of RWA1-resistant germplasm (STARS 9301B, STARS 9577B), moderately resistant germplasm (MR-015), and susceptible varieties (Schuyler, Harrington, and Morex) under greenhouse conditions. Russian wheat aphid population levels also were determined 14 d after plant infestation. STARS 9301B exhibited strong resistance by showing only small differences in leaf damage and growth parameters from the feeding by the biotypes. STARS 9577B showed greater differences in damage by the Russian wheat aphid biotypes than STARS 9301B, yet, the ratings were still within the resistant category (e.g., chlorosis rating 2.3-4.9). Leaf chlorosis ratings for MR-015 ranged from 5.0 to 6.9 and fell within the moderately resistant to susceptible categories for all the biotypes. The greatest difference in leaf chlorosis occurred in Morex where RWA2 showed less virulence than the other biotypes. Feeding by the Russian wheat aphid biotypes produced only small differences in leaf rolling and plant growth within plant entries. Population levels of the Russian wheat aphid biotypes did not differ within barley entries (n = 610-971) at the termination of the study (14 d). From our research, we conclude that the new Russian wheat aphid biotypes pose no serious threat to the key sources of resistance in barley (STARS 9301B and 9577B).

Simulation of individual leaf areas in grain sorghum

Most crop simulation models that incorporate environmental conditions estimate leaf area development. The grain sorghum growth simulation model, SORKAM, calculates individual leaf area based on leaf number and maturity class. The objective of this study was to generalize present leaf growth routines in SORKAM to be independent of maturity since there are no generally accepted maturing classes. Modified relationships between leaf number and leaf growth parameters were developed from existing studies and were tested against independent detailed leaf growth data sets. The revised relationships improved the r 2 between simulated and actual individual leaf areas from 0.80 to 0.88, reduced the bias from 32 cm2 to 9 cm 2 , and the RMSE from 80 cm 2 to 52 cm 2 . With the improved simulation, estimated leaf area index through the season was also improved from the original SORKAM estimate (RMSE decreased from 0.77 to 0.63; RMSE: root mean square error). Although simulation of individual leaf areas was improved, total leaf area produced over the season was not.

Effects of NaCl salinity and water stress on growth and leaf water relations of Asteriscus maritimus plants

Potted plants of Asteriscus maritimus (L.) Less were submitted to water stress (during two consecutive cycles, irrigation water was withheld for 5 days followed by a recovery period of 25 days) and saline stress (150 days of exposure to 0, 70 and 140 mM NaCl daily irrigation) in order to assess the effect on leaf water relations and growth parameters. Plants under saline and water stress conditions showed lower biomass and an early reduction in leaf expansion growth. Both stresses promoted a substantial degree of stomatal regulation; but, in spite of this, the plants showed signs of leaf tissue dehydration, decreases in RWC and Ψ pd values. However, salt-treated plants, developed a NaCl inclusion mechanisms, underwent osmotic adjustment, which was able to maintain leaf turgor. Under both stress conditions g l was independent to plant water status in the range between –0.8 and 1.0 MPa. Under water stress conditions, midday leaf water potential showed a threshold value (around −1.1 MPa), below which leaf conductance remained constant. In the salt-treated plants, the gradual closure of the stomata over a wide range of Ψ md may be important in maintaining some level of photosynthesis.

Analysis of toxic and osmotic effects of sodium chloride on leaf growth and economic yield of sugarcane

Sugarcane (Saccharum officinarum L.) an important sugar crop, shows high sensitivity to salinity at various growth stages. This study was conducted to determine the comparative response of a salt-tolerant (CP-4333) and a salt-sensitive (CP-71-3002) sugarcane clone to the toxic or osmotic effects of sodium chloride at two growth stages. Clones indicated significant differences in terms of reductions in dry weight and area of leaves under salinity at the grand growth stage. Leaf dry weight was more affected than leaf area, resulting in reduced specific leaf weight. The tolerant clone produced supplementary tillers in greater number that appeared to offload the ion excess. Clones indicated significant difference with regard to increase in leaf Na+ and Cl- and decrease in K+, but no difference in K+:Na+ ratio. Na+ and Cl- were negatively correlated while K+ was positively correlated with leaf growth parameters, indicating an adverse effect of Na+ and Cl- and importance of K+ to salt tolerance. The tolerant clone displayed higher water content, water, and turgor potentials of leaf than sensitive clone, but the osmotic potential did not significantly change. Soluble sugars of tolerant clone indicated a ~2 fold increase over control, indicating their osmo-protective role. Free proline accumulation was more specific to the sensitive clone and was correlated with Na+ and Cl- showing its synthesis due to ion-toxicity. At maturity, increased salinity reduced the millable cane yield, extractable juice and juice-brix percentage, but increased juice osmolality. All these parameters were negatively correlated with EC, Na+, and Cl- and displayed their specific effect on the sugar levels in the internodes. In summary, ion-toxicity was the main determinant of salt tolerance at the grand growth stage while the osmotic component of NaCl mainly appeared to affect the transport of sucrose to stalks, followed by stimulated sucrolytic activity in the internodes, resulting in reduced final cane yield.

Drought effects on the dynamics of leaf production and senescence in field‐grown Medicago arborea and Medicago citrina

SummaryForage shrub production in the Mediterranean region is frequently limited by soil water availability. To study plant responses to water deficit under such conditions is important for improving crop management and for selecting better yielding forage shrub species. Pre‐dawn leaf water potential (Ψpd), plant leaf area (PLA), leaf area per stem (LAs), leaf appearance rate (LAR1;), leaf senescence rate (LSR), individual leaf area (LA) and maximal leaf elongation rate (LER) were studied throughout the year for Medicago arborea (MA) and Medicago citrina (MC) under irrigated (control) and low rainfall field conditions, at the experimental field site of the University of the Balearic Islands in Spain.With irrigation, the highest LA and LER were observed in autumn and spring and the lowest in winter and summer. LAR; was similar for both species in autumn and winter. Throughout the spring, LAR1 was higher for MC compared to MA. PLA was similar for both species during the autumn, winter and spring seasons; however, during the summer PLA of MA was significantly reduced by 53%. This decline was attributed to higher leaf senescence during seed maturity. As a consequence, MC maintained higher leaf area (∼ 5 m2 plant−1) than MA (3 m2 plant−1).Under natural field conditions, soil water deficit increased from February to late August. The main effect of water stress was a marked reduction in LAR1, LA and LER reflected in lower LAs and PLA. Leaf area was severely reduced for both species during the summer, but much more intensively in MA, which developed full leaf senescence. Thus, MC maintained higher PLA than MA (0.5 m2 compared to 0.0 m2). Throughout the year, but especially in the driest months, MC was superior to MA in leaf growth parameters and PLA.

Cotton responses to ultraviolet-B radiation: experimentation and algorithm development

The potential impact of an increase in solar ultraviolet-B (UV-B) radiation due to human activity on higher plants has been the subject of many studies. Little work has been carried out so far on cotton responses to enhanced UV-B radiation. The objective of this study was to determine whether or not the current and projected increases in UV-B levels affect cotton growth and development, and to quantify and develop UV-B radiation functional algorithms that can be used in simulation models. Two experiments were conducted during the summer of 2001 using sunlit plant growth chambers in a wide range of UV-B radiations under optimal growing conditions. Leaves exposed to UV-B radiation developed chlorotic and necrotic patches depending on the intensity and length of exposure. Along with changes in visible morphology, cotton canopy photosynthesis declined with increased UV-B radiation. The decline in canopy photosynthesis was partly due to loss of photosynthetic pigments and UV-B-induced decay of leaf-level photosynthetic efficiency (maximum photosynthesis) and capacity (quantum yield) as the leaves aged. The total leaf area was less due to smaller leaves and fewer leaves per plant. Less plant height was closely related to a shorter average internode length rather than a fewer mainstem nodes. The UV-B did not affect cotton major developmental events such as time taken to square, time to flower, and leaf addition rates on the mainstem. Lower biomass was closely related to both smaller leaf area and lower photosynthesis. The critical limit, defined as 90% of optimum or the control, for stem elongation was lower (8.7 kJ m −2 per day UV-B) than the critical limit for leaf expansion (11.2 kJ m −2 per day UV-B), indicating that stem elongation was more sensitive to UV-B than leaf expansion. The critical limits for canopy photosynthesis and total dry weight were 7 and 7.3 kJ m −2 per day, respectively. The identified UV-B-specific indices for stem and leaf growth and photosynthesis parameters may be incorporated into cotton simulation models such as GOSSYM to predict yields under present and future climatic conditions.

The impacts of UV-B radiation on the regeneration of a sub-arctic heath community

The effects of ultraviolet-B radiation on regeneration after disturbance of a natural sub-arctic heathland have been investigated. Areas of pristine dwarf shrub heath were denuded of all above ground biomass in 1992 and exposed to enhanced UV-B (simulating a 15% depletion of the ozone layer). The resulting regenerated stem and leaf growth parameters were measured after four years on three dwarf shrubs, Vaccinium myrtillus, V. uliginosum and V. vitis-idaea and the grass Calamagrostis lapponica; leaves of the three dwarf shrubs were also analysed for UV-absorbing compounds and carbohydrates. Regeneration irrespective of treatment was slow, with Empetrum hermaphroditum failing to regenerate at all. Vaccinium myrtillus showed the most rapid regeneration attaining much of its original biomass in four years. There was a significant interaction between UV-B and year of regeneration in V. myrtillus; annual stem length increment showed an initial stimulation of 75% under enhanced UV-B in the first year of regeneration while a reduction of 16% was observed in the fourth year. Both V. uliginosum and V. vitis-idaea showed a reduction in annual stem length increment as regeneration progressed with a greater than 50% reduction in stem increment in the fourth year of regeneration compared to the first. Vaccinium uliginosum also showed an initial reduction in stem length increment of 40% under enhanced UV-B. None of the species were affected by enhanced UV-B in terms of total regenerated stem and leaf biomass or UV-absorbing compounds in regenerated leaf tissue. Total leaf carbohydrate and the ethanol/water soluble fraction in V. uliginosum were significantly increased by 29% and 31% respectively under enhanced UV-B. This suggests either a stimulation of photosynthesis or a reduction in sink size for photo-assimilates. Results are discussed in the context of the extremely slow regeneration of sub-arctic heath communities and the implications of contrasting UV-B effects on the regenerative ability of different species.

Effects of Foliar Fertilization of Texas Southern High Plains Cotton: Leaf Nitrogen and Growth Parameters

Foliar fertilizers have become one of the many inputs used in cotton (Gossypium hirsutum L) production systems across the U.S. Cotton Belt. Their usefulness, however, in producing high yielding, high quality cotton remains to be resolved This study was conducted to determine the effects of foliar fertilizers on cotton: (i) lint and seed yields, (ii) plant dry weight, (iii) plant leaf area, and (iv) leaf nitrogen concentration. During the 1990 growing season, this study was conducted at the Texas Tech University Research Farm east of New Deal, TX, on a Pullman clay loam (fine, mixed, thermic, Torrertic Paleustoll). Six foliar treatments were incorporated into a randomized complete block design with six blocks. Treatments 2 (15-2-0 with Ca), 3 (8-32-5 with micronutrients), and 4 (8-8-8 with micronutrients) were commercial products and were applied in compliance with their manufacturers' recommendations. Treatments 5 and 6 (46-0-0) were applied at various rates. During the 1991 growing season, this study was conducted at an on-farm location northeast of Petersburg, TX. The soil at this location was also a Pullman clay loam. The same six foliar treatments were incorporated into a randomized complete block design with four blocks. Foliar treatments were applied during both growing seasons at 0, 2, 4, 6, and 8 wk after matchead square. One week after each treatment application, 10 plants were removed from each plot and divided into three nodal horizons: (i) from node 6 to node 9, (ii) from node 10 to node 13, and (iii) node 14 and above. Leaf total and nitrate N concentrations were determined by these nodal horizons. Also, at 1, 5, and 9 wk after matchead square, plant leaf areas and dry weights were determined. Lint yields were determined after a killing freeze in 1990 and after crop termination in 1991. Feed grade urea increased leaf total N concentrations during 1990, but these results were not repeated in 1991. Urea also increased leaf nitrate N during both growing seasons. However, plant leaf area and dry weight, and lint and seed yields were not significantly affected by foliar fertilizers. Cost-benefit analyses were not conducted due to the lack of a significant yield response from foliar fertilizers. We conclude none of the costs associated with foliar fertilization will be recovered in net returns.

High vapour pressure deficit and low soil water availability enhance shoot growth responses of a C4 grass (Panicum coloratum cv. Bambatsi) to CO2 enrichment

The hypothesis that shoot growth responses of C4 grasses to elevated CO2 are dependent on shoot water relations was tested using a C4 grass, Panicum coloratum (NAD-ME subtype). Plants were grown for 35 days at CO2 concentrations of 350 or 1000 µL CO2 L-1. Shoot water relations were altered by growing plants in soil which was brought daily to 65, 80 or 100% field capacity (FC) and by maintaining the vapour pressure deficit (VPD) at 0.9 or 2.1 kPa. At 350 µL CO2 L-1, high VPD and lower soil water content depressed shoot dry mass, which declined in parallel at each VPD with decreasing soil water content. The growth depression at high VPD was associated with increased shoot transpiration, whereas at low soil water, leaf water potential was reduced. Elevated CO2 ameliorated the impact of both stresses by decreasing transpiration rates and raising leaf water potential. Consequently, high CO2 approximately doubled shoot mass and leaf length at a VPD of 2.1 kPa and soil water contents of 65 and 80% FC but had no effect on unstressed plants. Water use efficiency was enhanced by elevated CO2 under conditions of stress but this was primarily due to increases in shoot mass. High CO2 had a greater effect on leaf growth parameters than on stem mass. Elevated CO2 increased specific leaf area and leaf area ratio, the latter at high VPD only. We conclude that high CO2 increases shoot growth of C4 grasses by ameliorating the effects of stress induced by either high VPD or low soil moisture. Since these factors limit growth of field-grown C4 grasses, it is likely that their biomass will be enhanced by rising atmospheric CO2 concentrations.

The importance of water‐soluble carbohydrate reserves on regrowth and root growth of Lolium perenne (L.)

AbstractThis glasshouse study aimed to determine the relative importance of water‐soluble carbohydrates (WSC) and current photosynthate on root and top regrowth of perennial ryegrass (Lolium perenne L.). Individual plants were arranged in one of two miniswards (Experiments 1 and 2) and underwent varying defoliation frequencies designed to obtain a gradient of WSC content at the final harvest of each treatment (H1), when all treatments were defoliated. In Experiment 1, the plants were defoliated either three times at the one new leaf per tiller stage of regrowth (treatment 3 × 1), once at the two‐leaf and again at the one‐leaf stage (treatment 2, 1), once at the one‐leaf and again at the two‐leaf stage (treatment 1, 2) or once only at the three‐leaf stage (treatment 1 × 3), up to H1. Leaf and root growth and other parameters were assessed over 6 d after H1 in sunlight, and over a 4‐week period in darkness, and related to initial plant WSC content. In Experiment 2, plant defoliation treatments were: 3 × 1, 1, 2 or 1 × 3. Leaf regrowth was assessed for 36 d until the plants had three fully expanded new leaves per tiller.Leaf regrowth in both experiments was significantly related to stubble WSC (below 50 mm height).In Experiment 1, plants were almost fully reliant upon plant reserves for the first 3 d of regrowth, with reliance decreasing up to 6 d. When regrowth of plants was compared after 1 week in light or in darkness, it was estimated that one‐third of leaf regrowth was due to plant WSC reserves and the remainder due to photosynthesis. However, the capacity to photosynthesize and to grow roots after H1 was also significantly related to stubble WSC content.In Experiment 2, there was a significant difference (P<0·01) between defoliation treatments on leaf dry matter (DM) yield at 12 d (×1 leaf tiller−1) of regrowth, and this was, as in Experiment 1, significantly positively related to WSC content in the stubble. However, after 36 d of regrowth, DM yield of plants defoliated at 2 or 3 leaves tiller−1 up to H1 were similar, and both were significantly higher (P<0·01) than regrowth of plants defoliated at the one‐leaf stage.After defoliation, the period of reliance on WSC reserves may be substantially increased in situations of shading (canopy competition or cloud cover) or if the new regrowth shoot is removed by regrazing.

The Relationship Between Size of Shoot Apices and Morphological Features of Mature Leaves and Stems of Four Species of Angiosperm Trees

Shoot apex, leaf and stem growth parameters for four species of deciduous trees were measured. Only in elm was there a correlation between the size of shoot apical meristems and mature leaves. In ash, basswood and cottonwood there was no significant difference between size of shoot apices of sucker and canopy branches, despite significant differences in lamina size. In the sucker branches of all species studied there occurred an early, lateral expansion of the subapical region of the shoot apical meristem. This correlated well with the greater diameter of stem and pith regions of sucker branches. In addition, the season's annual ring of xylem was greater in basswood, cottonwood and elm. Diameters of vessel elements were greater in sucker than canopy branches in three of the four species. Total branch and internode and number of nodes per branch were significantly greater for sucker branches than canopy growth of all species studied.A hypothesis is proposed to explain the development of the very large surface area of leaves on sucker branches. This hypothesis is based on the position of sucker branches in relation to the root system and involves differences in water stress known to be present in all plants.

Leaf Growth and Photosynthetic Response to Nitrogen and Phosphorus in Seedling Trees of Gmelina arborea

Plants were grown in sand cultures under controlled conditions using nutrient solutions which were adjusted with respect to either nitrogen (N) or phosphorus (P) concentrations (two separate experiments) with other elements non-limiting. Leaf expansion at successive nodes was measured non-destructively and analysed according to the Richard's function, revised to provide geometrically meaningful parameters that could be linked with the dynamics of leaf growth. The reparameterised form describes sigmoidal increase in area (W) over time (t) as follows: W(t)= Wx(1+der(1+d)(to-t))-(1/d) where W, (cm2) is the asymptotic value of W for large t, to (days) is the time at which W(t) undergoes its point of inflexion, r (days-1) is the relative rate of lamina expansion of W(t) at to, and d determines the shape of the curve W versus t, so that the inflexion point occurs further up the curve with larger d. A comparison between N and P effects on leaf expansion parameters in plants showing similar net reduction in leaf mass and stem volume showed that Wx was more influenced by low N, whereas r was more sensitive to low P. A given reduction in canopy area due to nutrient deficiency was thus mainly attributable to smaller leaves on low N, but to fewer leaves on low P. Leaf photosynthesis (light-saturated in air) showed a curvilinear increase with tissue N and P, saturating above c. 2.5 mmol N (g dm)-1 and 100 μmol P (g dm)-1 in N and P experiments respectively. Leaf growth parameters Wx and r showed a similar dose response and highlight a potential use of those indices for analysis of growth response to N and P nutrition.

Light Intensity Influences Growth and Leaf Physiology of Aucuba japonica `Variegata'

Leaf physiology and growth parameters of Aucuba japonica (Thunb.) cv. Variegata were assessed under conditions of full sun (photosynthetic photon flux = 1531 to 2073 μmol·m-2·s-1) and under shadecloth (light transmittance of 69%, 47%, and 29% full sun) over 2 years. Two days after treatment initiation, net CO2 assimilation (A) was proportional to light level, although stomata1 conductance to water vapor (gs) was not influenced by shading. Subsequently, A, gs, transpiration rate, and water use efficiency of 100% sun-grown plants were often <50% that of shade-grown plants. After 1 month of exposure to 100% sun, leaves were chlorotic and necrotic; plant appearance was normal for plants grown under shadecloth. The growth index and total, leaf, stem, and root dry weights were inversely related to light level. Relative water content and chlorophyll concentration in leaves that had expanded before treatment initiation were reduced with increasing levels of irradiance, but these variables were not altered in leaves produced after treatment initiation. Plants from all treatments experienced dieback when transplanted to the field under conditions of full sun. We conclude that A. japonica is shade obligate, performing best with exposure to 47% of full sunlight.

Rate of fruit development, leaf growth, and earliness in determinate tomatoes

The component subperiods of reproductive development as well as rate of leaf growth were determined for three trusses in eight determinate tomato (Lycopersicon esculentum L. Mill) genotypes in an attempt to identify effective selection criteria for improving earliness. Days from transplanting to anthesis and first red fruit to the first truss correlated well with days to plant maturity (r = 0.58 and r = 0.63 respectively; P < 0.01). These correlations were stronger for full season genotypes (r = 0.53 to r = 0.69) than for early maturing genotypes (r < 0.41). Plant maturity was correlated moderately better with these periods in the later trusses than in the first truss. Leaf growth parameters were not correlated significantly with either earliness or fruit yield. Key words: Tomato, Lycopersicon esculentum, earliness

Morphogenèse foliaire et activité photosynthétique chez le soja (Glycine max)

The main stem development and the photosynthetic activity of leaves 2 to 9 were studied in soja (Glycine max (L.) Merr.) at the leaf blade extension and adult stages. A correlation between the different leaf growth parameters (rates, durations) and the phyllochrone has been demonstrated. That correlation varied with the age and rank of the leaf. Moreover, the existence of correlations between net photosynthesis on one hand and the rate of development and the leaf growth kinetics on the other hand reveals an interdependence between photosynthesis and morphogenesis. [Journal translation]

Light, Leaf Expansion and Seed Yield in Sunflower

Two sunflower hybrids, Hysun 31 and Suncross 150, were grown in the field with adequate irrigation and given three light treatments throughout their life cycle. The treatments were 100, 50 and 20% sun (high, medium and low light); during the vegetative period the high light treatment averaged more than 20 MJ m-2 day-1 total short-wave radiation. The two cultivars, although differing in many of the leaf and plant growth parameters measured, followed the same trends with respect to light. A reduction from 100 to 50% light delayed the appearance of leaves slightly but had no effect on patterns of leaf-area expansion such as the rate and duration of expansion of individual leaves and the distribution of leaf area among nodes. A further reduction in light, however, significantly reduced the size of all leaves through effects on the rates at which leaves expanded. There was no effect of light level on the period for which leaves expanded. Whilst leaf expansion remained unaffected by a reduction from high to medium light, specific leaf weight was significantly reduced to 76% of control levels. The lowest light regime further reduced specific leaf weight to only 59% of control levels. Total plant weights declined to 89% (not significant) at the medium light level and significantly to 47% at the low level and as harvest index was marginally, though not significantly, decreased by a reduction in light, these values translated into significant reductions in seed production (86 and 44% of controls).

Leaf-growth Parameters Associated with Photosynthetic Capacity in Expanding Leaves of Capsicum frutescens L.

The previously reported increase in photosynthetic capacity during laminar expansion up to an area of 10 cm2 is shown, in part, to be a function of the increasing cell surface area available for chloroplast growth. This occurs in a similar manner in the first eight leaves despite large differences in cell size. During this phase the increase in ribulose diphosphate activity is greater than can be accounted for by total chloroplast volume and develops independently of chlorophyll content. These two chloroplast components also have different developmental patterns after leaves have attained an area greater than 10 cm2.