Values Of Net Assimilation Rate Research Articles

Consistent response to topographical variation in net assimilation rate across the central Himalayan broadleaved forests

In a mountainous landscape, vegetation patterns are influenced by the interaction of slope aspect and topographical positions. Here, we have examined the effect of two contrasting aspects (North and South) and three slope positions (Hill Base, Mid Slope and Hill Top) on net assimilation rate (NAR) of trees across four forest sites of the monsoonal Central Himalaya between 400 and 2300 m elevations. The study species, namely Shorea robusta, Quercus leucotrichophora, and Q. floribunda were broadleaved evergreen with concentrated summer leaf drop and simultaneous leafing. The NAR of these broadleaved species was measured in five seasons (pre-monsoon, monsoon, autumn, winter and spring) diurnally at their respective forest sites. In each of the forest site the dominant species was the same, on both aspects and the three slope positions. We also analyzed topographical associated effect of tree water relations on NAR, using the data of an earlier study on these species. The average NAR (μ mol m−2 s−1) across the four forest sites and five seasons, (measured diurnally) was higher on the north (5.08 ± 0.23) slope aspect than south aspect (4.61 ± 0.22; average of 120 NAR values for each aspect), and among the three slope positions, it was higher on hill base (5.13 ± 0.29), than on mid-slope (4.80 ± 0.27) and hill top (4.61 ± 0.26; average of 80 NAR values for each position). These patterns in NAR values in relation to slope aspects and slope positions were also found separately for each of the species, and each of the seasons. The NAR varied across the sites, seasons and day time from 2.84 to 11.99 μ mol m−2 s−1, largely because of the variation in tree water potential and leaf phenological changes. To conclude, the NAR shows a consistency in responses to differences in slope aspects and slope positions across the forests ranging from tropical to warm temperate type. The study would help generalizing topographical effects on tree growth.

Assessing the effect of heavy metals on maize (Zea maysL.) growth and soil characteristics: plants-implications for phytoremediation

BackgroundHeavy metal pollution has become a global environmental issue. Heavy metals are contaminating the agro-soils, growing crops, and vegetables through different agricultural practices. In this study, besides the phytoremediation potential of maize, the role of chromium (Cr) and lead (Pb) on crop and soil health has been investigated.MethodsTwo maize varieties, Pak-Afgoi and Neelem, were grown under varying concentrations of Cr (50–300 ppm) and Pb (30–300 ppm) and different growth parametersi.e., seed germination, leaf size/number, stem girth, plant height, biomass, chlorophyll content, relative growth rate (RGR), and net assimilation rate (NAR) were studied under Cr and Pb stress. Likewise, the effect of metals was also assessed on different soil characteristics including soil texture, pH, EC, soil organic matter, urease activity and nutrients.ResultsStudied plant attributes were adversely affected by heavy metals toxicity. Affected values of RGR and NAR showed a linear correlation with affected growth and dry matter yield of maize. Heavy metals impacted different soil parameters including soil microbial performance and revealed a declining trend as compared to control soil. Maize varieties showed a significant phytoremediation potentiali.e., uptake of Cr and Pb was 33% and 22% in Pak-Afgoi, while Neelem showed 38% and 24% at 300 ppm, respectively. Data regarding metal translocation factor (TF), bioaccumulation factor (ACF), and biomagnification ratio (BMR) significantly revealed the potential of maize varieties in the removal of Cr and Pb metals from affected soils. However, Cr-accumulation was higher in shoots, and Pb accumulated in plant roots showed a differential behavior of metal translocation and affinity with the varieties. These maize varieties may be recommended for general cultivation in the Cr and Pb-contaminated areas.

Unlocking the secrets of wheat production: Evaluating phosphorus levels and seeding rates in alluvial soil conditions

A research study was conducted to determine the effect of different P levels and seeding rates on the growth, phenology, and yield of wheat. The experiment used a randomized complete block design with split plot arrangement and four replications. The main plots consisted of six seeding rates, ranging from 50 to 175 kg/ha, while the sub-plots received six different P levels, ranging from 50 to 200 kg/ha. In consecutive years, the study revealed significant effects of phosphorus levels, seeding rates, and their interaction on various growth characteristics and yield parameters of wheat. These included days to 50% heading and 50% maturity, leaf area index (LAI), leaf area duration (LAD), crop growth rate (CGR), net assimilation rate (NAR), and grain yield (GY). Phosphorus (P) level of 140 kg/ha resulted in the highest CGR, NAR, and GY in both years of the study. At a seeding density of 125 kg/ha, similar findings were observed, with the maximum CGR, NAR, and GY recorded. The highest interaction values for CGR, NAR, and GY were achieved with the combination of 140 kg P/ha and a seeding rate of 125 kg/ha. By utilizing a seed rate of 175 kg/ha and a P level of 200 kg/ha, the study revealed the highest values for LAI and LAD. Additionally, the maximum protein content was observed in treatments where seeds and P were applied at 50 and 200 kg/ha, respectively. In summary, the study provided conclusive evidence that the application of suitable seeding rates and P levels can yield significant improvements in the growth, phenology, and yield of wheat. The findings could be beneficial for farmers and researchers in improving wheat production.

Effect of varieties and nitrogen levels on growth indices of malt barley (Hordeum vulgare) under saline water irrigation

A field experiment was conducted during the winter (rabi)season of 2017–18 and 2018–19 at the Chaudhary Charan Singh Haryana Agricultural University, Hisar, to study the effect of saline water irrigation on growth indices in 4 varieties (‘BH 902’, ‘BH 946’, ‘BH 885’ and ‘DWRB 101’) of barley (Hordeum vulgare L.) at different nitrogen levels (0, 30, 60 and 90 kg/ha). The results showed that, during early growth period both 6-row barley varieties ‘BH 902’ and ‘BH 946’ recorded significantly higher crop-growth rate (CGR), relative growth rate (RGR), net assimilation rate (NAR), specific leaf weigth (SLW) and leaf-area duration (LAD) than both 2-row barley varieties ‘BH 885’ and ‘DWRB 101’, whereas ‘BH 885’ and ‘DWRB 101’ varieties attained higher values of RGR and NAR after 90 days after sowing (DAS). The CGR and LAD recorded maximum values between 61 and 90 DAS, while RGR and NAR showed the highest values up to 30 DAS irrespective of varieties and nitrogen levels. Application of 90 kg N/ ha significantly enhanced the CGR up to 90 DAS, RGR up to 30 DAS and LAD up to 120 DAS, while NAR values were significantly increased up to 60 DAS with 30 kg N/ha and SLW up to 90 DAS with 60 kg N/ha. The RGR, NAR and SLW were significantly decreased with the application of different nitrogen levels between 91 and 120 DAS as compared to the control. The variety ‘BH 946’ gave the highest grain yield of 5.15 t/ha, being 5.1, 7.3 and 14.7% higher than ‘DWRB 101’, ‘BH 902’ and ‘BH 885’, respectively. Different varieties responded to N application only up to 60 kg/ha. Grain yield of barley was positively correlated with CGR, SLW and LAD but negatively with RGR.

Effect of organic sources of nitrogen on physiological parameters of king chilli (Capsicum chinense Jacq.) under poly house condition

A study was conducted in rabi season 2019-20 in the poly-house, Department of Horticulture, CAU, Imphal to observe the effect of organic sources of nitrogen on net assimilation rate, relative growth rate and plant growth efficiency of king chilli (Capsicum chinense Jacq.) under poly house condition. The layout of the experiment was RBD (Randomized Block Design) with three replications under 8 different treatments. Results of the present experimentation revealed that the application of 100% RDF (T8) registered significant values for net assimilation rate (0.0232 g/m2/day), relative growth rate (0.0574 g/g/day) and plant growth efficiency (57.41%) at 60-90 DAT stage. However, among the organic sources, application of 100% RDN through vermicompost (T3) had significant effect on the physiological parameters of the crop which was comparable with that of inorganics treatment.

CRECIMIENTO DE PLÁNTULAS DE NUEVE GENOTIPOS DE Bouteloua curtipendula CON DOS TAMAÑOS DE CARIÓPSIDE

Establecer praderas en temporal árido representa un reto, por lo que un rápido desarrollo de la plántula implica ventajas. El presente estudio tuvo como objetivo evaluar el crecimiento inicial de Bouteloua curtipendula (Michx.) Torr. proveniente de dos tamaños de cariópside. El material vegetal incluyó a las variedades NdeM-125, NdeM-303, NdeM-417, NdeM-La Resolana y los genotipos CP-62 (Coahuila), CP-Centauro (Durango), CP-Teloxtoc (Puebla), CP-Ñañú1 (Hidalgo) y CP-Mixe (Oaxaca), con tamaños de cariópside grande (CG) y chico (CCh). Cariópsides de cada tamaño se sembraron en almácigo en sustrato de suelo, tepezil (mineral inerte y liviano que facilita la aireación y capilaridad) y corteza molida de árbol a razón 2:1:1. Se realizó trasplante en tubetes de 70 cm3 21 días después de siembra (dds) bajo un diseño completamente al azar. Se realizaron muestreos destructivos a los 43, 56, 67, 81 y 96 días después de siembra (dds) en condiciones de invernadero. Se determinó el peso de los componentes morfológicos en cada muestreo y se calculó la tasa absoluta de crecimiento (TAC), área foliar específica (AFE), tasa relativa de crecimiento (TRC) y tasa de asimilación neta (TAN). Se realizó análisis de varianza y prueba de comparación de medias de Tukey (P ≤ 0.05). El rendimiento de materia seca (MS) de componentes morfológicos fue diferente (P ≤ 0.05) a 56 dds y se observó que sembrar CG en NdeMLa Resolana resultó en mayor MS aérea y radical y mostró mayor peso de inflorescencia (P ≤ 0.05) a 81 y 96 dds. Los valores máximos para TAN y TRC ocurrieron en etapas iniciales y disminuyeron a mayor edad de planta para todos los materiales. En TRC, NdeM-125 con CG fue mayor conforme avanzó la edad de la planta, mientras en TAN, CP-Ñañú1 mostró mayores valores (P ≤ 0.01). El AFE fue mayor para todos los materiales a 81 y 96 dds y CP-Mixe con CCh fue el mejor tratamiento. Seleccionar por tamaño de cariópside resulta en desarrollo diferencial de plántula. Las plantas de NdeM-La Resolana a partir de ambos tamaños de cariópside mostraron producción de semilla precoz, lo que resulta valioso para auto-recuperación de agostaderos.

DESENVOLVIMENTO INICIAL E EFICIÊNCIA DE USO DE ÁGUA E NITROGÊNIO POR MUDAS DE <i>Calophyllum brasiliense, Eucalyptus urograndis, Tabebuia impetiginosa </i> E <i>Toona ciliata</i><sup>1</sup>

O conhecimento sobre o desenvolvimento inicial das mudas é fundamental para o sucesso de atividades de reflorestamento e de plantio em florestas naturais. O objetivo deste trabalho foi avaliar o desenvolvimento inicial e a eficiência de uso de água e nitrogênio por mudas de quatro espécies florestais nativas e exóticas (Calophyllum brasiliense (nativa), Eucalyptus urograndis (exótica), Toona ciliata (exótica) e Tabebuia impetiginosa (nativa)) com idade de aproximadamente 120 dias após a semeadura por 120 dias após o transplante em condições de casa de vegetação. Foram realizadas amostragens destrutivas para avaliar a biomassa seca (folha, caule, raiz e total), área foliar, relação raiz/parte aérea e nitrogênio total nas mudas. Com base nessas variáveis, foram calculados os parâmetros fisiológicos de crescimento e a eficiência de uso de água, que foi obtida pela razão entre o total de biomassa seca acumulada e a evapotranspiração dos vasos no período, determinada através de pesagens diárias em balança de bancada. Ao final de 240 dias após a semeadura, Calophyllum brasiliense e Tabebuia impetiginosa apresentaram maior produção de biomassa seca total e Toona ciliata apresentou maior relação raiz/parte aérea. Não houve diferenças entre a taxa de crescimento relativo das espécies avaliadas. Eucalyptus urograndis, Toona ciliata e Calophyllum brasiliense apresentaram os maiores valores de razão de área foliar, Toona ciliata, Tabebuia impetiginosa e Eucalyptus urograndis apresentaram os maiores valores de área foliar específica, Eucalyptus urograndis e Calophyllum brasiliense apresentam os maiores valores para razão de massa foliar e Tabebuia impetiginosa, Toona ciliata e Eucalyptus urograndis apresentaram os maiores valores de taxa de assimilação líquida. Com base na quantificação do nitrogênio total, Tabebuia impetiginosa e Toona ciliata foram as espécies mais eficientes no uso do nitrogênio. Eucalyptus urograndis apresentou a maior evapotranspiração enquanto Calophyllum brasiliense e Tabebuia impetiginosa foram as espécies mais eficientes no uso de água.

Growth Analysis of Chickpea var. Bari Chola-7 Following Application of TIBA (2, 3, 5- Triiodobenzoic Acid)

An investigation was made to see the effect of different concentrations (10, 20, 30 and 40 ppm) of 2, 3, 5- triiodobenzoic acid (TIBA) on leaf area index (LAI), leaf area duration (LAD), crop growth rate (CGR), relative growth rate (RGR) and net assimilation rate (NAR) of a cultivar of chickpea (Cicer arietinum L.) grown during rabi season of 2015 - 2016. Results revealed that LAI and LAD showed a positive response from flowering stage to maturity (66 - 110 DAS) due to 30 ppm TIBA application with maximum LAI and LAD occurring at the flowering stage. At 66 - 83 and 83 - 97 DAS, CGR was highest with the application of 30 ppm TIBA, while RGR was highest due to 10 ppm TIBA. Peak CGR was recorded at the time of pod setting to pod filling stage (8 - 97) and increased over control by 29.64%. Irrespective of the treatments, NAR was recorded maximum during flowering stage to pod setting (66 - 83 DAS) and thereafter decreased till maturity. At 66 - 83 and 83 - 97 DAS, maximum NAR values were recorded due to 30 ppm TIBA and the increases were 9.09 and 32.69% higher over the control, respectively.Journal of Bangladesh Academy of Sciences, Vol. 40, No. 2, 199-205, 2016

Growth indices and grain yield attributes in six maize cultivars representing two era of maize breeding in Nigeria

Growth parameters such as seedling germination attributes, crop growth rate (CGR), relative growth rate (RGR), net assimilation rate (NAR) and leaf area ratio (LAR) as well as yield parameters were investigated in six maize cultivars representing two era of maize breeding in Nigeria during the 2005 late and 2006 early cropping seasons. Differences between maize breeding era were significant for seedling emergence (E %) and emergence index (EI) while genotypes within a particular breeding era (G/E) differed significantly for E% and emergence rate index (ERI). Seasonal (S) variation in seedling parameters was also significant for E % and ERI with a 15% higher seedling emergence in 2006 early season. CGR in the genotypes in breeding era 1 was higher by seven percent (7%) during vegetative growth phase but lower by 14% at flowering phase compared to genotypes in breeding era 2. NAR on the other hand was consistently higher in varieties developed in 1970’s by 15.2 and 13.8% compared to varieties developed in 1990’s. Regardless of the breeding era, varieties with higher values for LAR at flowering (except var. TZPB-SR) were higher yielding than those with lower LAR. Overall, varieties developed in era 2 were superior to those developed in era 1 for E% and also had six percent (6%) higher values for LAR at vegetative growth phase than those developed in era 1 but decreased by two percent (2%) at flowering phase. E% in the genotypes ranged from 48.56 in ACR 9943 DMRSR to 79.33 in ACR99TZL COMP4 DMRSR, while EI and ERI ranged from 0.86 and 0.010 in TZB-SR to 0.96 and 0.014 in ACR 97 TZL COMP1-W. Grain yield was significantly higher in 2006 early cropping season by 0.3t/ha -1 translating to 14.78% than in late season and it ranged from 1.64t/ha -1 in TZPB-SR (era 1) to 2.94t/ha -1 in ACR99TZLCOMP4DMRSR (era 2). Var. ACR99TZL COMP4DMRSR with the lowest values for CGR, RGR and NAR at vegetative phase had the highest grain yield (2.94t/ha -1 ) indicating that genotypic superiority for grain yield is not particularly related to differences in any of these traits but rather dependent on the inherent genetic potential of the varieties themselves. Keywords: Zea mays L., Growth indices, Maize breeding era, Grain yield

Study of physiological growth indices of chickpea in chickpea (Cicer arietinum) + mustard (Brassica juncea) intercropping system under different weed management practices

The field experiments were carried out during rabi season of 2009-10 and 2010-11 at the Research Farm of Sher-e-Kashmir University of Agricultural Sciences and Technology of Jammu, Chatha to assess the physiological growth indices in chickpea+mustard intercropping system under different weed management practices. The significant superiority of replacement series treatment for leaf area index of chickpea over additive series treatment was noticed. The crop of sole chickpea was followed by replacement and additive series treatments in recording highest dry matter, crop growth rate and net assimilation rate values. Sole stand of chickpea recorded numerically higher relative growth rate (RGR) followed by replacement and additive series treatments. Weed free treatment recorded numerically the highest crop growth rate (CGR) and net assimilation rate (NAR) of chickpea at all the stages of observation. Sole chickpea produced higher yield as compared to chickpea+mustard when grown in additive and replacement series in the respective order.

Study of physiological growth indices of mustard in chickpea (Cicer arietinum) + mustard (Brassica juncea) intercropping system under different weed management practices

A field experiment was carried out during rabi seasons of 2009-10 and 2010-11 at the Research Farm of Sher-e-Kashmir University of Agricultural Sciences and Technology at Chatha, Jammu to assess the physiological growth indices in chickpea+mustard intercropping system under different weed management practices. The significant superiority of replacement series treatment for leaf area index of mustard over additive series treatment was noticed. The sole crop of mustard was followed by replacement and additive series treatments in recording highest dry matter, crop growth rate and net assimilation rate values. Sole stand of mustard recorded numerically higher relative growth rate (RGR) followed by replacement and additive series treatments. Weed free treatment recorded numerically highest crop growth rate (CGR) and net assimilation rate (NAR) of mustard at all the stages of observation. As regards yield, sole stand recorded significantly higher values of grain and was followed by additive and replacement series which in turn were differed significantly from one another in chickpea+mustard intercropping system.

Comparative Study of the Effect of Telfairia Mosaic Virus (TEMV) on the Growth Characteristics of Two Ecotypes of Telfairia occidentalis (Hooker Fil)

The effect of Telfairia Mosaic Virus (TeMV) on the growth characteristics of two ecotypes of Telfairia occidentalis was investigated. Seeds of T. occidentalis obtained from Akparabong in Ikom Local Government Area of Cross River State were designated ecotype A and seeds from Eket in Eket Local Government Area of Akwa Ibom State were designated ecotype B. Infection of T. occidentalis by TeMV caused significant reductions (p<0.05) in leaf area, shoot height, leaf number, leaf fresh and dry weight, fresh and dry weight of shoot and root. Percentage difference values for the above parameters were 57.19, 40.10, 46.59, 25.0, 24.5, 31.65, 37.43, 30.78, 19.97, 37.01 and 21.94% for ecotype A and B in infected samples compared to healthy controls. The virus also induced (p<0.05) reductions in Relative Growth Rate (RGR), with percentage difference values for ecotype A and B ranging from 21.1-21.7, 17.5 and 28.2%, with values for Net Assimilation Rate (NAR) for ecotype A and B ranging from 22.1-39.3 and 20.5-34.4%, respectively and percentage difference values for Leaf Area Ratio (LAR) for ecotype A and B ranging from 13.9-26.0 and 15.0-25.3%, respectively. Telfairia mosaic virus infection caused significant (p<0.05) reductions in RGR, NAR and LAR in inoculated plants of ecotypes studied compared to the healthy controls with ecotype A being more susceptible to the effect of TeMV infections than ecotype B. The virus also reduced the quality of the vegetable. Since, the difference in plant growth between infected and healthy plants depend on infection, this explains the difference in growth and plant size. These reductions in plant growth characteristics induced by TeMV infection alter the metabolism and subsequently dry matter yield of T. occidentalis.

Reakce růstových parametrů papriky na rozdílné úrovně výživy NPK

This work was conducted to study the effect of five NPK fertigation levels on the growth rate of sweet pepper (Capsicum annuum L. cv. Bruyo) grown under the plastic greenhouse using different growth analysis formulas. Leaf area ratio (LAR), specific leaf area (SLA), relative growth rate (RGR) and net assimilation rate (NAR) was evaluated in two periods (60–90 and 90–120 days after transplanting). The mean values of LAR, SLA, RGR and NAR tended to decrease significantly with advancing plant age in both seasons. In general, at the moderate level (34N-42P-29K / plastic house 540 m2) was found the highest significant values of LAR and SLA in the two growth periods. On the other hand, the highest values of NAR were recorded at the plants treated with the lowest NPK fertigation level (17N-21P-15K / plastic house 540 m2). However, increase of NPK fertigation doses to the moderate levels had favorable effects on LAR and SLA of sweet pepper plants.

Effect of Watering Regimes and Water Quantity on the Early Seedling Growth of Picralimanitida (Stapf)

Competing land use pattern has necessitated planting of useful forest trees on marginal lands with varying water status. A study was conducted on the effect of watering regimes and water quantity on seedlings growth of P. nitida. Seedlings were raised from seeds, transplanted in polythene bags and subjected to watering at full capacity daily, once in 3 days, 5 days; 20 ml daily, 3 days, 5 days; 15 ml daily, 3 days, 5 days; 10 ml daily, 3 days, 5 days; and flooding. The growth traits assessed were plant height, collar diameter, number of leaves; shoot, root and leaf dry weights as well as leaf area. The effect of watering regime and water quantity were significant (P ? 0.05) on quantitative morphological parameters of seedlings. Total dry weight and root dry weight were lower in both water-stressed and waterlogging than well-watered conditions, but the lowest values were obtained under flooding. However, specific leaf area (SLA) and leaf area ratio (LAR) were higher in water-stressed conditions than well-watered conditions. Relative growth rate of seedlings is related more to the net assimilation rate values than LAR and SLA. Also, root/shoot ratio was highest under daily full capacity watering. Thus, daily watering at full capacity with water availability or 15-20 ml of water per seedling during scarcity is recommended for raising P. nitida seedlings.

Effect of farmyard manure and mineral fertiliser on the growth of maize (Zea mays L.) in a long-term experiment II. Using the hunt-parsons program for plant growth analysis

In a long-term continuous maize experiment set up in 1959, the functional method of growth analysis was applied to investigate the effect of various levels of farmyard manure and mineral fertilisation on the growth of maize (Zea mays L.) and on the dynamics of the growth parameters over a 3-year period (2005–2007). The experiment involved two nutrient levels (based on the active agent equivalence principle): Level l: the NPK equivalent of 35 t ha−1 farmyard manure (FYM), applied in the form of FYM, FYM + mineral fertiliser or mineral fertiliser; Level 2: the NPK equivalent of 70 t ha−1 farmyard manure (FYM), applied in the form of FYM, FYM + mineral fertiliser or mineral fertiliser. The computerised growth analysis program elaborated by Hunt and Parsons (1974) was used to describe the effect of FYM and mineral fertiliser and to evaluate the results. This program fits functions to calculate the absolute growth rate (AGR), the relative growth rate (RGR), the net assimilation rate (NAR) and the leaf area ratio (LAR).The Hunt-Parsons program fitted a third-degree function to the dynamics of total dry matter production and second- or third-degree functions to that of the leaf area growth. The highest mean values of AGR were obtained in treatments with the higher level of mineral fertiliser alone or mineral fertiliser + FYM when the weather was favourable (2.05–2.31 g plant−1 day−1), and in treatments with the lower quantity of mineral fertiliser alone or mineral fertiliser + FYM in the case of dry weather (1.73–1.74 g plant−1 day−1). In 2005 and 2006 the absolute growth rate gave a good characterisation of the various fertiliser effects, which exhibited high values with significant differences, while in 2007 lower AGR values were obtained and no fertiliser effects were observed. In the dry year (2007) the maximum values of NAR and LAR were higher in all the treatments than in the wetter years (except at the lower rate of mineral fertiliser alone). In the case of NAR, the results obtained with the functional method of growth analysis, based on function fitting, were easier to interpret than those obtained using the classical method.It was concluded from the results that in long-term experiments the use of the functional method of growth analysis gave a more precise evaluation of the effects of fertiliser treatments and the year on the growth of maize in the vegetative growth stage and on the mean and maximum values of growth parameters.

Growth rhythms in sunflower (Helianthus annuus L.) in response to environmental disparity.

Sunflower hybrids maintain high level of stability in a variety of environments. Environmental variations affect and modify plant attributes like growth, development and assimilation through physio-morphic functions, thus modifying plant phenology. Field experiments, one each in spring and autumn, were conducted at Pir Mehr Ali Shah, Arid Agriculture University, Rawalpindi, Pakistan for two years (2007 and 2008) to document the effect of environmental variations on growth rhythms of sunflower hybrids. Four Sunflower hybrids, Alisson-RM, Parasio-24, MG-2 and S-278 were planted in randomized complete block design with four replications. The data based on physiological attributes like leaf area (LA), specific leaf area (SLA), crop growth rate (CGR) and net assimilation rate (NAR) at 10 days interval after complete emergence to 60 days after emergence (DAE) were recorded. Overall higher values of LA, SLA, CGR and NAR were recorded during spring as compared to autumn for both years. LA, CGR and NAR of all the hybrids followed a sigmoid curve pattern during both seasons; however, at the start of the season lesser values were observed during spring as compared to autumn. SLA exhibited an opposite trend and continuously decreased till the end. Sigmoid curve pattern of LA, CGR and NAR may be related to environmental variables like temperature and sunshine hours. The decrease after a peak may be due to senescence of older leaves and shifting of crop from vegetative to reproductive phase.

Growth of marandu palisadegrass subjected to strategies of intermittent stocking

Grazing strategies alter sward leaf area patterns of growth, affecting herbage accumulation and utilisation. The objective of this experiment was to evaluate the growth of marandu palisadegrass (Brachiaria brizantha cv. Marandu) swards subjected to strategies of intermittent stocking. The experiment was carried out in Piracicaba, São Paulo, Brazil, from October/2004 to September/2005. Swards were grazed at 95 and 100% canopy light interception (LI) to post-grazing heights of 10 and 15 cm, following a 2 × 2 factorial arrangement with four replications in a randomised complete block design. The response variables evaluated were: crop growth rate, relative growth rate, net assimilation rate, leaf area ratio and leaf weight ratio. In early and late spring, the highest crop growth rate was recorded for treatment 95/15 (11.2 and 10.1 g m-2 day-1, respectively), along with high values of net assimilation rate (4.4 and 6.9 g m-2 day-1, respectively), leaf area ratio (0.0095 and 0.0103 m-2 g-1, respectively) and leaf weight ratio (0.56 and 0.56 g g-1, respectively). To compensate reductions in net assimilation rate plants made some morphological and physiological adjustments increasing leaf area and leaf weight ratio. Relative growth rate and net assimilation rate were 26 and 50% higher, respectively, on swards grazed at 95% than at 100% LI. In early spring treatments 100/10 and 95/15 resulted in the highest relative growth rate (0.086 and 0.059 g m-2 day-1, respectively). Treatment 95/15 resulted in the most favourable pattern of growth (crop growth rate, relative growth rate, net assimilation rate), particularly during the transition period between winter and spring.

Effect of Athenium and Nitrogen in some growth parameters of local class Coriandrum sativum L.

The study was carried out in Al-Rashccdia station-department of agricultural researeh-Ninavaduring the season 2001-2002. Anexperimentdone in field with siltv loam soil in order to investigate the e fleet of cthephon(0,240,480,720) gr./ha a,i, , and Nitrogen (0. 60, 80, 100, 120) Kg. /ha on some growth parameters of local Coriander (Coriandrumsativum L.) The results showed an increase in the values of Net Assimilation Rate (N.A.K) . Relative Growth Rale(R.G.R) , Crop Growth Rario (C.G.R) and Biological Yield by increasing the rate of Nitrogen specially at 80 kg/ha . but on the other side etticphon at all levels indicated inhibition in growth values at N.A.R. , R.G.R. , and C.G.R. except for the values of biological yields witch increased at the rate of ethephon 240 and 480 er/ha.

Duração do período de descanso e crescimento do dossel de Panicum maximum cv. Mombaça sob lotação intermitente

O crescimento do dossel do capim-Mombaça foi analisado sob lotação intermitente com três períodos de descanso (PD), tratamentos definidos em função do tempo necessário para a expansão de 2,5; 3,5 e 4,5 novas folhas por perfilho e período de pastejo de seis dias. A área experimental foi dividida em cinco ou seis piquetes por tratamento. Utilizaram-se cinco novilhos mestiços (holandês x zebu) por tratamento, como animais de prova, além de outros, como animais de equilíbrio, que foram adicionados, quando necessário, para garantir índice de área foliar (IAF) residual de 2,0, ao final do 6(0) dia de cada período de pastejo. O estudo constou de duas fases de crescimento: 1) após roçada de uniformização, no início da estação de pastejo e 2) após alguns ciclos de pastejo, sob efeito dos três PDs. Os piquetes receberam adubação em cobertura de N, P2O5 e K2O, na dose de 50; 12,5 e 50 kg/ha, no início dos crescimentos 1 e 2. A intervalo médio de seis dias, durante 45 dias, estimaram-se a intercepção da radiação fotossinteticamente ativa (RFA), o IAF e a massa seca de forragem verde (MSFV). Aos dados de MSFV e de área foliar foram ajustados polinômios de segundo grau em função da idade, a partir dos quais foram estimados os valores instantâneos de biomassa e IAF e, a partir destes, as taxas de crescimento relativo (TCR) e de assimilação líquida (TAL) e a razão de área foliar (RAF), para cada idade. A intercepção da RFA pelo dossel evoluiu assintoticamente, alcançando valores máximos entre 95 e 98%, enquanto os valores de IAF e MSFV experimentaram incrementos ainda na faixa de estabilidade da intercepção da RFA. Os valores de TCR, TAL e RAF exibiram evolução assintótica decrescente. A grande proporção de colmo do dossel, ao final do PD mais longo, favoreceu a TCR e a TAL.

Análise de crescimento do capim-elefante 'Napier' adubado e irrigado

Avaliaram-se os índices de crescimento taxa de crescimento relativo (TCR), taxa assimilatória líquida (TAL), razão de área foliar (RAF), índice de área foliar (IAF) e a interceptação luminosa do capim-elefante 'Napier' após pastejo. O trabalho consistiu de dois experimentos, com quatro tratamentos de adubação de N e K, em kg/ha (T1: 100 kg de N e 80 kg de K, T2: 200 kg de N e 160 kg de K, T3: 300 kg de N e 240 kg de K e T4: 400 kg de N e 320 kg de K), sendo um irrigado e outro sem irrigação, segundo o delineamento de blocos ao acaso com três repetições. A análise estatística observou um esquema de parcela subdividida, tendo nas parcelas as doses de N e K e nas sub-parcelas as idades de rebrotação após pastejo (2, 8, 15, 45 e 123 dias), para IAF e interceptação de luz. O IAF na área irrigada aumentou de 0,28 para 8,27, média dos quatro tratamentos de N e K, entre a menor e maior idade de rebrotação. Na área não irrigada, também ocorreu um aumento no IAF, embora de menor magnitude que na área irrigada, de 0,16 para 7,76. Os valores médios de TCR, TAL e RAF foram 0,0083 g/g.dia, 3,57 g/cm².dia e 0,0021 m²/g, respectivamente. A interceptação de luz aumentou com o aumento do IAF, estabilizando-se no 51,5º dia. Já a penetração de luz no interior do dossel diminuiu assintoticamente em função do IAF. O coeficiente de extinção variou de 0,29 na maior combinação de N e K, para 0,53 nas doses de 200 kg/ha de N e 160 kg/ha de K.