Effects of light, temperature, and rate of desiccation on translucency in wheat grain

1968 ◽  
Vol 19 (3) ◽  
pp. 365 ◽  
Author(s):  
JA Parish ◽  
NJ Halse
Keyword(s):  
Low Temperatures ◽  
Dry Weight ◽  
Grain Filling ◽  
Wheat Grain ◽  
Low Light ◽  
Wide Range ◽  
Grain Drying ◽  
Drying Techniques ◽  
Laboratory Results ◽  
Grain Filling Period

Wheat grain was harvested at maximum dry weight and dried under various conditions in the laboratory. Results showed that opaque grain was produced by fast drying; translucency developed with slow drying. The effect of various temperatures when drying rate was constant was also measured. It was found that translucency developed more at high temperatures than at low temperatures. There was little "mottling" despite the wide range between treatments from entirely opaque to fully translucent grain. Drying techniques were found whereby grain samples different in texture but identical in other respects can be prepared. In other experiments wheat plants were grown in controlled light and temperature conditions during the grain-filling period. Results showed that at this stage low temperature and low light intensity favoured the development of translucency.

Effects of yellow spot on wheat: comparison of epidemics at different stages of crop development

1983 ◽  
Vol 34 (1) ◽  
pp. 39 ◽  
Author(s):  
RG Rees ◽  
GJ Platz
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Severe Disease ◽  
Dry Weight ◽  
Grain Filling ◽  
Yellow Spot ◽  
Early Disease ◽  
Area Index ◽  
Crop Development ◽  
Grain Filling Period

Effects of yellow spot (Pyrenophoua tuitici-repentis) on two cultivars (Banks and Olympic) of wheat have been examined in a field experiment where distinctly different epidemics were produced in various treatments. Severe yellow spot before jointing reduced production of both tillers and dry matter, and substantially lowered leaf area index at jointing. Severe disease after jointing reduced leaf area index at flowering, dry weight of plants at maturity and harvest index. Crop phenology was also modified, with flowering being delayed by early disease and crop maturity hastened by late disease. Where yellow spot was severe throughout, the grain-filling period was greatly reduced. Grain yield of Banks was reduced by c. 13 % by early disease, c. 35 % by late disease, and c. 48 % by disease throughout the crop season. Most of the loss was in reduced grain size. Although yield loss in Olympic was less than in Banks, the resistance of Olympic was shown to be inadequate.

Jojoba: Temperature Adaptation as Expressed in Growth and Leaf Function

1983 ◽  
Vol 10 (3) ◽  
pp. 299 ◽  
Author(s):  
IF Wardlaw ◽  
JE Begg ◽  
D Bagnall ◽  
RL Dunstone
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
Vascular System ◽  
Starch Content ◽  
Dry Weight ◽  
Co2 Exchange ◽  
Temperature Adaptation ◽  
Pulse Labelling ◽  
Wide Range ◽  
Young Leaves

The adaptation of jojoba [Simmondsia chinensis (Link) Schneider] to temperature was studied under controlled conditions. Shoot extension and leaf area development reflected the very low rate of growth of this species, even under favourable conditions, and were stable with an increase in temperature from 20 to 30°C. However growth was markedly reduced at temperatures below 20°C and at 6°C there was no net gain in dry weight over a 42 day period. Root: shoot ratios were near unity and showed a small drop in response to increasing temperature. Leaves adapted to low temperature by an increase in thickness, specific leaf weight and starch content. Chlorophyll formation was retarded in young leaves developing at 15/10°C, but there was no sign of photodestruction of previously formed chlorophyll in mature leaves. Young leaves developing at 30/25°C had a very high chlorophyll a/b ratio of 9.5, but otherwise leaf chlorophyll was apparently normal (2.3-3.4) over a wide range of temperatures. Light saturation of net CO2 exchange (NCE) occurred at about 1000 �E m-2 s-1 for leaves grown over a wide range of temperatures and the maximum NCE of approximately 16 mg CO2 dm-2 h-1 (0.45 mg m-2 s-1) occurred between 19 and 25°C. Pulse labelling with 14CO2 indicated that low temperature (18°C) reduced the rate of transfer of 14C from the primary products of fixation to sucrose. The rate of movement of 14C-labelled photosynthate out of the leaf was negligible at 18°C, and reached only about 3% h-1 at 30°C. In the stems, shortly after 14CO2 uptake by the leaf, 86% of the 14C activity was in sucrose, indicating that this was the preferred form of translocate in the vascular system. However glucose was more abundant in the leaves than sucrose, particularly at low temperatures. Starch accumulated in the leaves at low temperatures, reaching nearly 30% of the dry weight at 18/13°C. Photosynthetic stability rather than active adaptation appears to form the basis of resistance to temperature stress in jojoba. With low rates even under optimal conditions this is essentially one of adaptation for survival rather than adaptation for production.

Modelling climatic risks of aflatoxin contamination in maize

2008 ◽  
Vol 48 (3) ◽  
pp. 358 ◽  
Author(s):  
Y. S. Chauhan ◽  
G. C. Wright ◽  
N. C. Rachaputi
Keyword(s):  
Risk Index ◽  
Grain Filling ◽  
Aflatoxin Contamination ◽  
Climatic Data ◽  
Seasonal Temperature ◽  
Sowing Time ◽  
Wide Range ◽  
Climatic Risks ◽  
Grain Filling Period ◽  
Lower Temperature

Aflatoxins are highly carcinogenic mycotoxins produced by two fungi, Aspergillus flavus and A. parasiticus, under specific moisture and temperature conditions before harvest and/or during storage of a wide range of crops including maize. Modelling of interactions between host plant and environment during the season can enable quantification of preharvest aflatoxin risk and its potential management. A model was developed to quantify climatic risks of aflatoxin contamination in maize using principles previously used for peanuts. The model outputs an aflatoxin risk index in response to seasonal temperature and soil moisture during the maize grain filling period using the APSIM’s maize module. The model performed well in simulating climatic risk of aflatoxin contamination in maize as indicated by a significant R2 (P ≤ 0.01) between aflatoxin risk index and the measured aflatoxin B1 in crop samples, which was 0.69 for a range of rainfed Australian locations and 0.62 when irrigated locations were also included in the analysis. The model was further applied to determine probabilities of exceeding a given aflatoxin risk in four non-irrigated maize growing locations of Queensland using 106 years of historical climatic data. Locations with both dry and hot climates had a much higher probability of higher aflatoxin risk compared with locations having either dry or hot conditions alone. Scenario analysis suggested that under non-irrigated conditions the risk of aflatoxin contamination could be minimised by adjusting sowing time or selecting an appropriate hybrid to better match the grain filling period to coincide with lower temperature and water stress conditions.

Growth kinetics of Marquis wheat. II. Carbon dioxide dependence

1972 ◽  
Vol 50 (4) ◽  
pp. 883-889 ◽  
Author(s):  
F. D. H. Macdowall
Keyword(s):  
Carbon Dioxide ◽  
Light Intensity ◽  
Carbon Dioxide Concentration ◽  
Dry Weight ◽  
Maximum Growth ◽  
Carbon Dioxide Enrichment ◽  
Low Light ◽  
Growth Coefficient ◽  
Light Intensities ◽  
Wide Range

Marquis wheat was grown in growth rooms with four different concentrations of carbon dioxide and four to seven different intensities of light in a 16-h photoperiod at 25 °C. Growth was expressed quantitatively as the pseudo-first-order rate coefficient. Carbon dioxide stimulated growth, but the effect was greater the lower the light intensity in opposition to the known effect on photosynthesis. Carbon dioxide and light, in effect, did not influence the "rate" of growth of wheat additively but, rather, mutually compensated over a wide range. The growth coefficient of the roots was a little less than that of the shoots at all carbon dioxide concentrations and light intensities, probably owing to the cost of translocation. However, root growth benefited most from carbon dioxide enrichment at low light intensities. At intermediate light intensity there appeared to be a carbon dioxide concentration optimal for shoot growth. Carbon dioxide enrichment did not influence the maximum growth coefficient of Marquis wheat with respect to light intensity. The light-using efficiency of growth, calculated for vanishingly low light intensity at which it is maximal, was maximal for shoots at 1300 ppm CO2 but that for laminal area and root dry weight increased with CO2 to 2200 ppm at which the value for "leaves" was nearly fourfold that for roots. Unlike photosynthesis, the stimulation of growth by raised CO2 concentration was accomplished by increased efficiency of, and not capacity for, the net photosynthetic use of light.

Water Relations of the Developing Wheat Grain

1980 ◽  
Vol 7 (5) ◽  
pp. 519 ◽  
Author(s):  
EWR Barlow ◽  
JW Lee ◽  
R Munns ◽  
MG Smart
Keyword(s):  
Water Deficit ◽  
Flag Leaf ◽  
Maximum Level ◽  
Grain Filling ◽  
Controlled Environment ◽  
Wheat Grain ◽  
Grain Filling Period ◽  
Pigment Strand ◽  
Days After Anthesis ◽  
Wheat Spike

The physiological and anatomical mechanisms underlying the reduced sensitivity of wheat grain growth to water deficits in the post anthesis period have been investigated. The water potential (Ψ) and water content of the developing wheat grain and of other tissues within the wheat spike and flag leaf were compared under controlled environment and field conditions. In the 14 days following anthesis when the amount of water in each grain was increasing, the Ψ gradient between the grain and the rest of the plant was most pronounced. This Ψ gradient disappeared when the water per grain reached its maximum level (15 days after anthesis). The apparent turgor potential (P) of the wheat grain was very small (less than 0.2 MPa) throughout the grain filling period. When water was withheld 10 and 20 days after anthesis, the grain Ψ changed little despite a large decrease in the Ψ of the glumes, rachis and flag leaf. Grain Ψ showed the same independence during a diurnal cycle of water deficit. The independence of grain Ψ under water deficit conditions may be related initially to the xylem discontinuity in the floral axis and, in longer-term water stress situations, to the deposition of lipid in the pigment strand of the grain itself.

scholarly journals Physiological Traits Determining Yield Tolerance of Wheat to Foliar Diseases

2017 ◽  
Vol 107 (12) ◽  
pp. 1468-1478 ◽  
Author(s):  
F. van den Berg ◽  
N. D. Paveley ◽  
I. J. Bingham ◽  
F. van den Bosch
Keyword(s):  
Carbon Assimilation ◽  
Grain Filling ◽  
Specific Weight ◽  
Water Soluble ◽  
Strong Positive Correlation ◽  
Area Index ◽  
Disease Tolerance ◽  
Wide Range ◽  
Mechanistic Basis ◽  
Grain Filling Period

Tolerance is defined as the ability of one cultivar to yield more than another cultivar under similar disease severity. If both cultivars suffer an equal loss in healthy (green) leaf area duration (HAD) over the grain filling period due to disease presence, then the yield loss per unit HAD loss is smaller for a more tolerant cultivar. Little is understood of what physiological and developmental traits of cultivars determine disease tolerance. In this study, we use a mathematical model of wheat to investigate the effect of a wide range of wheat phenotypes on tolerance. During the phase from stem extension to anthesis, the model calculates the assimilate source and sink potential, allowing for dynamic changes to the source–sink balance by partitioning assimilates between ear development and storage of water-soluble carbon (WSC) reserves, according to assimilate availability. To quantify tolerance, rates of epidemic progress were varied on each phenotype, leading to different levels of HAD loss during the postanthesis, grain-filling period. Model outputs show that the main determinant of tolerance is the total amount of assimilate produced per grain during the rapid grain-fill period, leading to a strong positive correlation between HAD per grain and tolerance. Reductions in traits that affect carbon assimilation rate and increases in traits that determine the amount of structural biomass in the plant increase disease tolerance through their associated reduction in number of grains per ear. Some of the most influential traits are the canopy green area index, carbon use efficiency, and leaf specific weight. Increased WSC accumulation can either increase or decrease tolerance. Furthermore, a cultivar is shown to be maximally tolerant when a crop is able to just fill its total sink size in the presence of disease. The model has identified influential functional traits and established that their associations with tolerance have a mechanistic basis.

Dry matter accumulation and distribution in winter wheat grown in a humid continental climate

1981 ◽  
Vol 59 (3) ◽  
pp. 415-420 ◽  
Author(s):  
L. A. Hunt ◽  
L. V. Edgington
Keyword(s):  
Winter Wheat ◽  
Dry Matter ◽  
Dry Weight ◽  
Grain Filling ◽  
Triticum Aestivum L ◽  
Dry Matter Accumulation ◽  
Maximum Value ◽  
Grain Filling Period ◽  
Green Coloration ◽  
Continental Climate

The growth of a crop of 'Arrow' winter wheat (Triticum aestivum L. em Thell.) was studied in detail from 2 weeks before ear emergence to maturity. Aboveground dry weight increased up to 4 weeks after ear emergence, when it reached a maximum value of 1.4 kg∙m−2, and then decreased marginally. The rate of aboveground dry matter accumulation over a 6-week period beginning 2 weeks before ear emergence averaged 24.4 g∙m−2∙day−1.Rapid ear growth commenced some 2 weeks after ear emergence and continued until after the crop had lost all green coloration. Dry matter accumulation in the ears in the period beginning 3 weeks past ear emergence was greater than accumulation in the aboveground parts of the crop as a whole. This indicated that much of the ear dry matter increase in the latter part of the grain filling period occurred as a result of translocation of previously accumulated assimilates. The stem fraction (including leaf sheaths), the major aboveground reservoir of material that is translocated to the ear, decreased from 800 g∙m−2 at 3 weeks after ear emergence to 493 g∙m−2 at maturity.

Growth and yield of highland maize in Mexico

1974 ◽  
Vol 83 (2) ◽  
pp. 213-221 ◽  
Author(s):  
P. R. Goldsworthy ◽  
M. Colegrove
Keyword(s):  
Growth Rate ◽  
Grain Growth ◽  
Growth Rates ◽  
Dry Weight ◽  
Grain Filling ◽  
Growth And Yield ◽  
Weight Changes ◽  
Highland Maize ◽  
Grain Filling Period ◽  
Tropical Varieties

SUMMARYThe growth and yield of five highland varieties of tropical maize were studied. Grain yields were between 4·7 and 8·8 t/ha. Crop growth rates (C) increased to a maximum of between 25 and 35 g/m2/day at silking and then declined. Grain growth rates (maximum 21 g/m2/day) exceeded current C during most of the grain-filling period.After silking, when C exceeded grain growth rate, dry matter accumulated in the stem and husk, resulting in an increase of from 200 to 600 g/m2. Later, as grain growth rate increased and exceeded current C, some of this accumulated material was incorporated into the grain, and stem weight decreased. A comparison of the dry weight changes after flowering in these varieties with those reported for a hybrid that yielded 12 t grain/ha indicates that the smaller yield of the Mexican varieties was associated with smaller grain growth rates and the incorporation into the grain of a smaller fraction of the dry weight produced after flowering. These results suggest that the capacity of the grain ‘sink’ to utilize assimilates limited yields in the tropical varieties.

Persistence of Non-Crease Protophloem Strands in the Developing Wheat Grain

1990 ◽  
Vol 17 (2) ◽  
pp. 223 ◽  
Author(s):  
DB Fisher
Keyword(s):  
Grain Filling ◽  
Wheat Grain ◽  
Grain Filling Period

The two protophloem strands in the lateral ovary walls of the developing wheat grain, previously reported to be obliterated during grain elongation, are shown to persist through about half, or somewhat longer, of the grain filling period. During the latter part of their functional life, they appear to be involved in the absorption of solutes produced during degeneration of the middle pericarp. During the final stages of pericarp degeneration, the protophloem strands show a basipetal progression of degeneration and adherence to the remaining inner and outer pericarp layers.

Growth and yield of lowland tropical maize in Mexico

1974 ◽  
Vol 83 (2) ◽  
pp. 223-230 ◽  
Author(s):  
P. R. Goldsworthy ◽  
A. F. E. Palmer ◽  
D. W. Sperling
Keyword(s):  
Grain Growth ◽  
Growth Rates ◽  
Dry Weight ◽  
Grain Filling ◽  
Growth And Yield ◽  
Weight Increase ◽  
Tropical Maize ◽  
Growing Period ◽  
Grain Filling Period ◽  
Tropical Varieties

SUMMARYThe growth and yield of three tropical varieties of maize were studied at two elevations in Mexico: Poza Rica (60m) and Tlaltizapan (940m). Grain yields were between 3·5 and 8·5 t/ha. The growing period was longer and the crop produced more dry weight and yield at Tlaltizapan than at Poza Rica. Crop growth rates (C) increased to a maximum of about 35 g/m2/day at both sites and then declined. Grain growth rates (maximum 35 g/m2/day) exceeded current C during most of the grain filling period. After silking when C exceeded grain growth, dry matter accumulated in the stem. Later as grain growth increased and exceeded C, some of the accumulated material was incorporated into the grain and stem weight decreased. The dry weight increase after flowering was similar at the two sites, but the grain yield at Tlaltiapan was larger because a larger proportion of the dry weight increase was incorporated into the grain than at Poza Rica. The results indicate that at both sites grain ‘sink’ capacity was limiting yield.

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