Effects of autotrophic biomass and composition on photosynthesis, respiration and light utilisation efficiency for a tropical savanna river

2018 ◽  
Vol 69 (8) ◽  
pp. 1279 ◽  
Author(s):  
Simon A. Townsend ◽  
Ian T. Webster ◽  
Michele A. Burford ◽  
Julia Schult
Keyword(s):  
Incident Light ◽  
Dry Weight ◽  
Tropical Savanna ◽  
Wet Season ◽  
Chl A ◽  
Fold Reduction ◽  
Underwater Light Climate ◽  
Efficiency Parameter ◽  
Tightly Coupled ◽  
Utilisation Efficiency

The efficiency of light used for photosynthesis, when standardised for areal chlorophyll (Chl)-a biomass, is summarised by the light utilisation efficiency parameter and is dependent on light at the water’s surface, the underwater light climate and autotroph characteristics. Herein we examined the relationships between light, photosynthesis, respiration and autotroph biomass in a tropical savanna river in northern Australia during the dry season when autotroph biomass accumulated following wet season disturbance. The river’s autotrophs comprised mainly benthic microalgae, macroalgae and macrophytes. Total Chl-a and dry weight biomasses increased 4- and 27-fold respectively over 5 months, whereas photosynthesis doubled. Photosynthesis was light limited and, when standardised for Chl-a and dry weight biomasses, declined with increasing biomass, despite increasing incident light through the study period. We surmised this was due to self-shading and autotrophic composition, which had variable Chl-a content and resulted in a 10-fold reduction in the light utilisation efficiency with increasing light and biomass. Because respiration was tightly coupled to photosynthesis, biomass-standardised respiration also decreased with increasing biomass. Autotrophic self-shading and composition can have significant effects on light utilisation efficiency and the biomass–photosynthesis relationship, and warrant consideration when interpreting photosynthesis for river health monitoring.

scholarly journals FORAGE PRODUCTION OF SOME LESSER-KNOWN LEUCAENA SPECIES GROWN ON ACID SOIL

2016 ◽  
Vol 6 (2) ◽  
pp. 46
Author(s):  
Nurhayati D. Purwantari
Keyword(s):  
Acid Soil ◽  
Calcareous Soils ◽  
Dry Weight ◽  
Forage Production ◽  
Fresh Weight ◽  
Wet Season ◽  
Edible Part ◽  
P Content ◽  
Significant Difference ◽  
Leucaena Species

Leucaena leucocephala leaves are nutritious and palatable for ruminants. However, the plant is poorly adapted on acid soil, water logged, and susceptible to psyllid (Heteropsylla cubana). Leucaena favours soils with pH >5. It performs best on calcareous soils. This study aimed to evaluate adaptability of several Leucaena species on acid soils. The study was conducted at the experimental field in Ciawi, Bogor, altitude 500 m above sea level, rainfall 1500-2000 mm year-1, on Latosol soil with pH 5.2. Leucaena species evaluated were L. leucocephala K28, L. leucocephala (local type), Leucaena KX2 hybrid, L. collinsii, L. trichandra, and L. diversifolia. Experiment was designed in a randomized complete block, four replications. All the seedlings were grown in the nursery for 2.5 months before being transplanted to the field. The plants were grown in row plots of 5 m x 1 m with planting distance 0.5 m and spacing between row plot was 3 m. One unit replicate was 5 m x 21 m. In wet season, the plants were pruned at 50 cm height every 3 months, whilst in dry season pruning was done every 5 months. Parameter measured were plant regrowth and forage production (edible part and non-edible part of the plant), as well as N and P content of the edible part. The result showed that Leucaena KX2 hybrid was superior to other leucaenas. Regrowth of KX2 hybrid was the fastest and produced highest forage. The highest fresh weight forage production for 1 year (four times harvests), i.e. 33.93 t ha-1 year-1 equal to 12.48 t ha- 1 year-1 of dry weight, was obtained from Leucaena KX2 hybrid, whereas the lowest was produced by L. diversifolia, i.e. 3.12 t ha-1 year-1 of fresh weight or 1.01 t ha-1 year-1 of dry weight. Production of non-edible part followed the pattern of production of edible part. N and P content in the edible part of all Leucaena species did not show any significant difference except for L. trichandra which contained the lowest. This study implies that Leucaena KX2 hybrid is adaptable to acid soil; therefore it can be grown in wider areas throughout Indonesia.

scholarly journals Photosynthesis sensitivity to NH4+-N change with nitrogen fertilizer type

2014 ◽  
Vol 60 (No. 6) ◽  
pp. 274-279 ◽  
Author(s):  
A. Nasraoui-Hajaji ◽  
H. Gouia
Keyword(s):  
Net Photosynthesis ◽  
Dry Weight ◽  
N Fertilization ◽  
Photochemical Quenching ◽  
Negative Effects ◽  
Ps Ii ◽  
Chl A ◽  
Inhibitory Site ◽  
Tomato Growth ◽  
Non Photochemical Quenching

N-fertilization type affected differently tomato growth. In the field experiment, hydroponic cultures were conducted using NO<sub>3</sub>-N (5 mmol); mixture of KNO<sub>3</sub>-N (3 mmol) and (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub>-N (2 mmol); NH<sub>4</sub><sup>+</sup>-N (5 mmol) or urea&nbsp;(5 mmol) as nitrogen source. Compared to nitrate, ammonium and urea had negative effects on morphology and dry matter production. Effects of the different nitrogen forms were investigated by measuring several photosynthesis parameters and chl a fluorescence. Two different significant types of reaction were found. When nitrogen was added as ammonium or urea, dry weight, chlorophyll tenor, transpiration rate, stomatal conductance and photosynthetic activity were inhibited. Supply of ammonium or urea, reduced the ratio (F<sub>v</sub>/F<sub>m</sub>), photochemical quenching and enhanced the non photochemical quenching. These data suggest that the adverse decrease in tomato growth under ammonium or urea supply may be related principally to inhibition of net photosynthesis activity. The high non photochemical quenching shown in tomato fed with ammonium or urea indicated that PS II was the inhibitory site of NH<sub>4</sub><sup>+</sup>-N which was directly uptaken by roots, or librated via urea hydrolysis cycle.

Herbicides for weed control in grain sorghum crops in the Northern Territory

1970 ◽  
Vol 10 (46) ◽  
pp. 588
Author(s):  
IMW Wood
Keyword(s):  
Good Control ◽  
Dry Weight ◽  
Grain Sorghum ◽  
Northern Territory ◽  
Research Station ◽  
Wet Season ◽  
Grain Yields ◽  
Stylosanthes Humilis ◽  
Townsville Stylo ◽  
Grass Weed

In experiments conducted in the 1968-69 wet season at the Katherine Research Station, Northern Territory, a number of herbicides gave good control of the grass weed Pennisetum polystachyon in grain sorghum crops. Linuron at 3 lb a.i. an acre and PCP at 20 lb a.i. an acre as pre-emergence applications effectively controlled grasses with no apparent adverse affects on the crop. With both there were significantly higher grain yields than on unweeded control plots containing an average of 1378 lb dry weight of P. polystachyon an acre. Fluometuron at 3 lb a.i. an acre late pre-emergence and early post-emergence and chlorthal at 7 lb a.i. an acre pre-emergence controlled grasses but did not increase grain yields. Further investigations are warranted with these herbicides, as banded applications to the interrow may overcome the apparent problem of crop phytotoxicity. Chlorthal at rates that gave good grass control had no adverse effect on Townsville stylo (Stylosanthes humilis). This could be an important advantage when sorghum is sown in rotation with Townsville stylo pasture or where the crop is undersown with Townsville stylo.

scholarly journals Numerical Assessments of Leaf Area Index in Tropical Savanna Rangelands, South Africa Using Landsat 8 OLI Derived Metrics and In-Situ Measurements

2019 ◽  
Vol 11 (7) ◽  
pp. 829 ◽  
Author(s):  
Timothy Dube ◽  
Santa Pandit ◽  
Cletah Shoko ◽  
Abel Ramoelo ◽  
Dominic Mazvimavi ◽  
...  
Keyword(s):  
South Africa ◽  
Leaf Area Index ◽  
Leaf Area ◽  
National Park ◽  
Dry Season ◽  
Kruger National Park ◽  
Landsat 8 ◽  
Tropical Savanna ◽  
Wet Season ◽  
Area Index

Knowledge on rangeland condition, productivity patterns and possible thresholds of potential concern, as well as the escalation of risks in the face of climate change and variability over savanna grasslands is essential for wildlife/livestock management purposes. The estimation of leaf area index (LAI) in tropical savanna ecosystems is therefore fundamental for the proper planning and management of this natural capital. In this study, we assess the spatio-temporal seasonal LAI dynamics (dry and wet seasons) as a proxy for rangeland condition and productivity in the Kruger National Park (KNP), South Africa. The 30 m Landsat 8 Operational Land Imager (OLI) spectral bands, derived vegetation indices and a non-parametric approach (i.e., random forest, RF) were used to assess dry and wet season LAI condition and variability in the KNP. The results showed that RF optimization enhanced the model performance in estimating LAI. Moderately high accuracies were observed for the dry season (R2 of 0.63–0.72 and average RMSE of 0.60 m2/m2) and wet season (0.62–0.63 and 0.79 m2/m2). Derived thematic maps demonstrated that the park had high LAI estimates during the wet season when compared to the dry season. On average, LAI estimates ranged between 3 and 7 m2/m2 during the wet season, whereas for the dry season most parts of the park had LAI estimates ranging between 0.00 and 3.5 m2/m2. The findings indicate that Kruger National Park had high levels of productivity during the wet season monitoring period. Overall, this work shows the unique potential of Landsat 8-derived metrics in assessing LAI as a proxy for tropical savanna rangelands productivity. The result is relevant for wildlife management and habitat assessment and monitoring.

Corrigendum to: Seasonal patterns of soil carbon dioxide efflux from a wet¿dry tropical savanna of northern Australia

2002 ◽  
Vol 50 (3) ◽  
pp. 373
Author(s):  
Xiaoyong Chen ◽  
Derek Eamus ◽  
Lindsay B. Hutley
Keyword(s):  
Root Growth ◽  
Soil Temperature ◽  
Dry Season ◽  
Soil Co2 Efflux ◽  
Co2 Efflux ◽  
Tropical Savanna ◽  
Northern Australia ◽  
Soil Co2 ◽  
Wet Season ◽  
Closed Chamber

Soil CO2 efflux rates were measured in a eucalypt open forest in a tropical savanna of northern Australia, with a portable closed chamber and CO2 gas analyser. Both abiotic (soil temperature and water content) and biotic (litterfall and fine-root growth) factors that may influence soil CO2 efflux were examined. Daytime rates of soil CO2 efflux rate were consistently higher than nocturnal values. Maximal rates occurred during late afternoons when soil temperatures were also maximal and minimum values were recorded during the early morning (0400–0800 hours). Average soil CO2 efflux was 5.37 mol m–2 s–1 (range 3.5–6.7 mol m–2 s–1 during the wet season and declined to 2.20 mol m–2 s–1 (range 1.2–3.6 mol m–2 s–1) during the dry season. The amount of carbon released from soil was 14.3 t ha–1 year–1, with approximately 70&percnt; released during the wet season and 30&percnt; during the dry season. The rate of efflux was correlated with soil moisture content and soil temperature only during the wet season, when root growth and respiration were high. During the dry season there was no correlation with soil temperature. These results are discussed in relation to the carbon balance of tropical savannas.

Australian canola germplasm differs in nitrogen and sulfur efficiency

2008 ◽  
Vol 59 (2) ◽  
pp. 167 ◽  
Author(s):  
Tatjana Balint ◽  
Zdenko Rengel ◽  
David Allen
Keyword(s):  
Genotypic Variation ◽  
Dry Weight ◽  
Breeding Programs ◽  
Relative Growth ◽  
Breeding Lines ◽  
Shoot Dry Weight ◽  
Sulfur Supply ◽  
Utilisation Efficiency ◽  
Low Sulfur ◽  
Low Nitrogen

Eighty-four canola genotypes, including current commercial Australian genotypes, some older Australian genotypes, new breeding lines, and several genotypes from China, were screened for nitrogen and sulfur efficiency in the early growth stage. Plants were grown in a glasshouse using virgin brown Lancelin soil (Uc4.22) supplied with basal nutrients. The treatments were: (i) adequate nitrogen and sulfur, (ii) low nitrogen, and (iii) low sulfur. Canola shoots were harvested at 38 days after sowing when growth reduction and the nitrogen and sulfur deficiency symptoms were evident in most genotypes. The nitrogen or sulfur efficiency in canola genotypes was evaluated on the basis of: (1) growth at low nitrogen or sulfur supply, (2) growth at low relative to adequate nitrogen and sulfur supply, and (3) nitrogen or sulfur utilisation efficiency expressed as shoot dry weight per unit of nitrogen or sulfur content in shoots. Genotypic variation in growth and nitrogen or sulfur efficiency in canola germplasm was significant. Two genotypes (Chikuzen and 46C74) were ranked efficient and 2 inefficient (CBWA-005 and Beacon) in uptake and utilisation of nitrogen under all 3 criteria. In terms of sulfur efficiency, genotype Argentina was ranked efficient, whereas CBWA-003 and IB 1363 were classified inefficient under all 3 criteria. Two canola genotypes (Surpass 600 and 46C74) were both nitrogen- and sulfur-efficient in terms of relative growth at low v. adequate nutrition; their use in the breeding programs could be considered.

Predictability of wheat growth and yield in light-limited conditions

2007 ◽  
Vol 145 (1) ◽  
pp. 63-79 ◽  
Author(s):  
F. D. BEED ◽  
N. D. PAVELEY ◽  
R. SYLVESTER-BRADLEY
Keyword(s):  
Solar Radiation ◽  
Grain Yield ◽  
Incident Light ◽  
Dry Weight ◽  
Water Soluble ◽  
Growth And Yield ◽  
Soluble Carbohydrates ◽  
Total Solar Radiation ◽  
Shoot Dry Weight ◽  
Source And Sink

In seeking better predictions of grain yield under light-limited conditions, shading was applied to field-grown winter wheat cv. Slejpner during each of five consecutive phases (canopy expansion, ear expansion, pre-flowering, grain expansion and grain filling). Absolute measures were taken of solar radiation and its effects on growth in three seasons, at a site where water and nutrient supplies were not limiting. Replicate mobile shades automatically occluded 0·80 of incident light when mean total solar radiation exceeded 250 J/m2 per s. Mean effects over seasons of shading on incident total solar radiation were −296, −139, −78, −157 and −357 MJ/m2 for the five phases respectively, and corresponding effects on shoot dry weight were −236, −184, −58, −122 and −105 g/m2. Estimated efficiency of radiation use after flowering was 1·2 g/MJ unshaded, tending to increase with shading. Shading in all phases reduced grain dry matter yield: mean effects over seasons were −106, −64, −61, −93 and −281 g/m2 for the five consecutive shading periods. Shading from GS31–39 increased mean maximum area of the two top leaves from 2700 to 3100 mm2 per leaf but, with fewer stems, canopy size remained unaffected. This and the next shading, from GS39–55, reduced specific leaf weight from 42 g/m2 by 4 and 3 g/m2 respectively, but effects on shoot dry weight were largely due to stem and ear. By flowering, stem weights, and especially their reserves of water-soluble carbohydrates, had partially recovered. Effects on yield of shading from GS31–39 were explained by a reduction in grains/m2 of 3070 from 26109. Shading from GS39–55 reduced grains/m2 by 4211 due to fewer grains per ear, whilst mean weight per grain increased in compensation. Shading from GS55–61 decreased grains/ear by 2·5. Shading from GS61–71 decreased ear growth and reduced stem weight, and at harvest resulted in 4·3 less grains/ear. Effects of the final shading from GS71–87 were fully explained by a reduction in mean dry weight/grain of 10·3 mg. Except for shading from GS71–87, source- and sink-based explanations of grain yield both proved feasible, within the precision of the measurements. Constraints to accurate comparison of source- and sink-based approaches are identified, and the implications for yield forecasting are discussed.

Algal composition and biomass in the tropical soda lake Chitu with focus on seasonal variability of Arthrospira fusiformis (Cyanophyta)

2016 ◽  
Vol 67 (4) ◽  
pp. 483 ◽  
Author(s):  
Tadesse Ogato ◽  
Demeke Kifle ◽  
Brook Lemma
Keyword(s):  
Seasonal Variability ◽  
Soda Lakes ◽  
Soda Lake ◽  
Dry Weight ◽  
Taxonomic Composition ◽  
Algal Community ◽  
Environmental Drivers ◽  
East African ◽  
Chl A ◽  
Algal Abundance

The vital ecological functions of the East African soda lakes are much dependent on Arthrospira, which forms a natural nearly monoalgal populations and serves as the main diet for the huge flocks of flamingos in the present study lake Chitu (Ethiopia). This study investigated algal taxonomic composition and biomass, and the seasonal variability in the abundance of Arthrospira fusiformis in response to some environmental drivers (e.g. rainfall, salinity and nutrients) using samples collected over an annual cycle. The algal community was composed of a few taxa (15 species), with exclusive dominance of A. fusiformis. Chlorophyll-a (Chl-a) and dry weight, and abundance of A. fusiformis were notably high and exhibited seasonal variations, with significantly (P<0.05) higher levels of Chl-a and dry weight during the rainy season. The observed strong correlations of algal abundance and biomass with rainfall (positively) and alkalinity-salinity (negatively), probably suggest that hydrological control of the salinity is the major driving force for the seasonal variability of A. fusiformis in the lake. Further hydrological modifications that enhance salinisation may greatly affect A. fusiformis thereby causing instability of the flamingos with eventual impairment of the ecosystem values of the lake.

The importance of environmental factors in soil fertility assessments. II.* Nutrient concentration and uptake

1974 ◽  
Vol 25 (2) ◽  
pp. 309 ◽  
Author(s):  
RC Stefanson ◽  
N Collis-George
Keyword(s):  
Soil Fertility ◽  
Soil Temperature ◽  
Nutrient Uptake ◽  
Physical Environment ◽  
Nutrient Concentration ◽  
Incident Light ◽  
Dry Weight ◽  
Plant Performance ◽  
Plant Responses ◽  
Wide Range

Lettuce plants were grown in two soils under a wide range of controlled conditions in the glasshouse. Assessments were made of the effect of soil temperature, incident light and season, in terms of the nutrient concentration and nutrient uptake in the plant tissue, which was analysed for nitrogen, phosphorus, potassium, magnesium, calcium and sodium. Both the concentration and the uptake of each nutrient were affected significantly by soil temperature and incident light, both between and within seasons. The type of soil had an effect on these estimations, but its significance could not be tested statistically. A considerable number of first and second order interactions between components of the physical environment affected the quantities being examined. These interactions were statistically significant. The value of each nutrient analysed, which is an aspect of plant performance, reflected changes in the physical environment independently of the other nutrients. Often a particular nutrient showed no coincident pattern of responses to the environment when these were measured in terms of dry weight, nutrient concentration in the tissue, or total nutrient uptake. Each nutrient concentration and each nutrient uptake varied as micrometeorological factors in the glasshouse changed. Hence, ambiguous assessments of soil fertility were obtained with all measured plant responses. ____________________ *Part I, Aust. J. Agric. Res., 25: 299 (1974).

scholarly journals EFFECT OF NaCl ON HYEMATOCOCCUS PLUVIALIS PRODUCTIVITY AND CONTENT IN ITS CELLS OF PHOTOSYNTHETIC PIGMENTS, ACTIVE OXYGEN FORMS AND ASTAXANTINE

2018 ◽  
Vol 63 (3) ◽  
pp. 263-275 ◽  
Author(s):  
N. G. Averina ◽  
N. V. Kozel ◽  
R. A. Sherbakov ◽  
M. S. Radyuk ◽  
E. E. Manankina ◽  
...  
Keyword(s):  
Photosynthetic Pigments ◽  
Haematococcus Pluvialis ◽  
Total Content ◽  
Dry Weight ◽  
Control Culture ◽  
Maximum Effect ◽  
Cell Diameter ◽  
Chl A ◽  
Dry Biomass ◽  
Β Carotene

The effect of NaCl (25, 50, 100, 200 and 300 mM) on the productivity of the Haematococcus pluvialis strain IBCE H-17 on such parameters as dry biomass, content of protein, photosynthetic pigments, as well as astaxanthin and reactive oxygen species (ROS) was studied. It was found that NaCl at low and medium concentrations (25, 50 and 100 mM) in the culture medium stimulated the accumulation of dry biomass during the first 7 days of cultivation on average 1,3 times as compared to the control (Rudik’s standard medium). After 12 days of incubation, stimulation averaged 33 % using 25 and 50 mM salt. The protein content on a dry weight basis fell, averaging 70 % of the control on the 7th day of incubation with 50–300 mM salt and 55 % on the 12th day for a salt concentration of 100–300 mM. When the algae was grown for 7 days on solutions containing NaCl, the total content of photosynthetic pigments – chlorophylls (Chl) a and b as well as the carotenoids neoxanthine, violaxanthin, lutein and β-carotene decreased. Chl b was more resistant to salinity than Chl a. Of all the pigments, NaCl exerts the greatest negative effect on β-carotene. Stress conditions created by NaCl led to the generation of ROS, in particular, after 7 days of cultivation the total ROS content in the “NaCl-100” variant was 1.7 times higher than that in the control culture and 3.0 times higher than the control in the 12-day culture. A significant positive effect of salinity on the content of astaxanthin was noted. The maximum effect was observed with 100 mM NaCl. After 7 days of incubation, the content of astaxanthin exceeded the control indices by 2.8 times, and after 12 days – by 20.5 times. The number of algae cells after 7 days of incubation in the “NaCl-100” variant decreased on average by 33 %, while the cell diameter increased by 29 %. 

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