Corresponding Author An Appraisal of Relative Levels of Starch, Reducing Sugars and Non-reducing Sugars Within Developing Grains of Wheat

Alireza Houshmandfar and Davood Eradatmand Asli; An appraisal of relative levels of starch, reducing sugars and non-reducing sugars within developing grains of wheat ABSTRACT Relative levels of starch, total sugars, reducing sugars and non-reducing sugars were studied at different grain locations within developing grains of wheat (Triticum aestivum L. var. PBW-343). The labeled spikes were sampled five times, seven-day intervals started from seventh day after anthesis (DAA) up to 28 th DAA, and at maturity. All the grains, irrespective of their locations in an ear, revealed a positive correlation between their ages and the levels of starch. The disparity between the bold and small grains in the levels of starch was maximum at 7 th DAA. The total sugars increased upto third week after anthesis in small grains in the proximal, middle or distal spikelets, while its values enhanced upto fourth week in the bolder grains in the same segments. The gap amongst the bold and small grains tended to taper with the grains' progression to maturity. When total sugars were studied as two separate components i.e., reducing and non-reducing sugars, it was deciphered that the absolute levels of reducing sugars were significantly more than the non-reducing sugars in all the grains irrespective of their locations in the spike or spikelet. The data sum up that bolder grains contained relatively higher levels of starch with concomitant lower levels of total, reducing and non-reducing sugars as compared to smaller grains which offered a contrasting picture with lower levels of starch and a higher level of total, reducing and non-reducing sugars

The link between transpiration and nutritional status in wheat grown under elevated CO2

© 2016 Dr Alireza HoushmandfarAtmospheric [CO2] is expected to reach 550 µmol mol-1 by 2050, 37% higher than the current concentration of approximately 400 µmol mol-1. Elevated [CO2] directly affects crop growth and development through the effects on net assimilation rates and stomatal conductance: Increasing intercellular [CO2] results in higher net assimilation rates (in C3 crops), thus higher biomass and grain production, and lower stomatal conductance, thus lower transpiration rate with higher leaf and canopy level water use efficiency. The reduced transpiration rate, however positive for dryland agriculture where water is nearly always the most limiting factor, is suggested to play a role in the reduction of nutritional status, often observed in crops grown under elevated [CO2]. This thesis predominantly used the Australian Grains Free Air CO2 Enrichment (AGFACE) facility with wheat to test whether a reduction in transpiration-driven mass flow of nutrients contributed to nutrient decline under elevated [CO2]. The potential CO2-driven changes in (i) the xylem nutrient concentrations, (ii) the relationship between nutrient uptake and transpiration rate, and (iii) the negative relationship between nutrient uptake and leaf level transpiration efficiency among wheat genotypes were investigated. At anthesis, both transpiration rate and xylem nutrient concentrations were lower under elevated [CO2], suggesting decreased delivery rate of nutrients to the shoot. On the other hand, averaged over longer periods during the growing season, transpiration rates and nutrient uptake were correlated under both ambient and elevated [CO2], but nutrient uptake per unit water transpired was higher in plants grown under elevated than ambient [CO2]. The negative relationship between nutrient uptake and transpiration efficiency among wheat genotypes remained unchanged under e[CO2]. These results suggest that reduced nutrient delivery rate in the transpiration stream contributes to decreases in nutrient concentration under elevated [CO2], but cannot fully account for the overall, more complex relationship between plant nutrition and elevated [CO2]

An Appraisal of the Yielding Ability and its Attributes among Different Cultivars of Bread Wheat under Field and Pot Conditions

ABSTRACT Yielding ability and its attributes among different cultivars of wheat (Triticum aestivum L.) namely PBW-154, PBW-343 and PBW-138 were investigated under field and pot culture conditions. At harvest, the tagged mother shoots were collected and observations were recorded on yield of grains (g), number of productive tillers, number of grains per ear, 1000 grain weight (g), number of spikelet, number of grain per spikelet, total dry matter and harvest index. The data infer that the variable yield performance of a variety could be traced to specific parameter(s) e.g., PBW-343, which out-yielded to the extent of approximately 14 and 8 percents higher than PBW-138 and PBW-154 respectively, had significantly a higher number of grains per ear. The PBW-343 also had a significantly higher number of grains per spikelet as compared to other two cultivars, which plausibly, contributed it with a higher grain numbers spike-1 in long term. By restricting the experimental observations only to the mother shoots in pot cultures trials, the findings unveiled consistency in variations amongst different varieties in their yielding abilities as well and the same could be linked to grain number per mother shoot and/or grain weights. There was an insignificant difference in PBW-343 grain weight as compared to PBW-154 which of course possessed significantly higher grain weight than PBW-138. The results of the present investigation surmise that the grain yield in wheat, whether under field or pot cultures conditions, was steered by a set of components like number of tillers M-2, grain number per ear and grain weight which contribute mutually towards the total build-up of the yield

An Appraisal of Copper, Zinc and Iron Accumulation at Different Grain Locations Within a Spike of Wheat Alireza Houshmandfar and Davood Eradatmand Asli: An Appraisal of Copper, Zinc and Iron Accumulation at Different Grain Locations Within a Spike of Whea

ABSTRACT Copper, zinc and iron levels were investigated at various grain types and positions within developing grains of wheat (Triticum aestivum L. var. PBW-343). Mother shoots were divided into three grain positions included proximal (spikelet No. 1 to 5), middle (spikelet No. 6 to 15), and distal (spikelet No. 16 to 20) regions, and further into two grain types within each spikelet included basal (bold) (grain No. 1 and 2) and apical (small) (grain No. 3 upward). The plants were grown in a screen covered hall under otherwise natural conditions. Grain dry weight, copper, zinc and iron levels were evaluated in ten labelled spikes which sampled at 14th and 28th day after anthesis (DAA), and at maturity. The levels of the aforementioned micronutrients declined as the grains progressed towards maturity. The bolder grains possessed relatively higher levels of copper, zinc and iron concentration at all the stages of grain development as compared to smaller grains. The levels of copper and zinc concentration were higher in middle position as compared to proximal and distal positions respectively. However, in the case of iron, the concentration decreased in an acropetal fashion, as it was more in proximal position than middle and distal positions respectively. The results suggest that the grains reflected variable profiles with regards to distributions of nutrients within spike as well as spikelet

Grain yield responsiveness to water supply in near-isogenic reduced-tillering wheat lines – an engineered crop trait near its upper limit

Tausz, M ORCiD: 0000-0001-8205-8561Grain yield responsiveness to water supply was evaluated in spring wheat (Triticum aestivum L.) near-isogenic lines (NILs) for presence of the reduced-tillering ‘tin’ (tiller inhibition) gene using boundary-line analysis. Data were collected from multiple seasons at Managed Environment Facilities (MEFs; field experimental facilities to control and target water supply) at three locations across the Australian wheatbelt. The minimum water required to obtain a measurable yield was less in reduced-tillering than free-tillering NILs (70 vs 95 mm). Above this minimum, for every mm increase in water supply, grain yield in free-tillering lines increased more rapidly (that is, showed greater responsiveness) than reduced-tillering lines (15.4 vs 12.6 kg ha−1 mm−1). This difference suggests the reduced-tillering gene is associated with greater yield potential in situations with water supply of less than 200 mm. Reduced-tillering wheat also affords a 0.3 t ha−1 yield benefit in extremely water-limited, low yielding situations where no measurable yield is expected with free-tillering wheats (i.e. at water supply 95 mm). These specific adaptations need to be considered when contemplating the use of reduced-tillering wheats in dryland systems where water is a key limiting factor. © 2018 Elsevier B.V

Crop rotation options for dryland agriculture: An assessment of grain yield response in cool-season grain legumes and canola to variation in rainfall totals

Tausz, M ORCiD: 0000-0001-8205-8561Crop production in dryland systems is mainly dependent on water availability from rainfall which is highly variable between years and locations. We employed the widely used boundary-line analysis, with an existing industry dataset from across the Australian dryland cropping regions, to investigate the relative sensitivity of grain yield in canola (Brassica napus L.), chickpea (Cicer arietinum L.), faba bean (Vicia faba L.), field pea (Pisum sativum L.), lentil (Lens culinaris L.), and narrow-leafed lupin (Lupinus angustifolius L.) to variation in rainfall totals. Chickpea had the lowest non-productive water use, was more responsive to water supply, and reached its maximum yield at a lower water supply than the other species. In contrast canola had the highest non-productive water use, was less responsive to water supply, and reached its maximum yield at a higher water supply than the other species. These results suggest that chickpea offers the most stable outcome, and canola the greatest variation, in response to the variability in rainfall totals between years and locations. © 2019 Elsevier B.V

Can elevated CO2 buffer the effects of heat waves on wheat in a dryland cropping system?

Tausz, M ORCiD: 0000-0001-8205-8561Increasing atmospheric CO2 concentration [CO2] drives the rise in global temperatures, with predictions of an increased frequency of heat waves (short periods of high temperatures). Both, CO2 and high temperature, have profound effects on wheat growth and productivity. We tested whether elevated [CO2] (eCO2) has a potential to ameliorate the effects of simulated heat waves (HT) on wheat in a dryland cropping system. Wheat was field-grown at the Australian Grains Free Air CO2 Enrichment (AGFACE) facility under ambient [CO2] (∼390 ppm) or eCO2 (∼550 ppm) for two growing seasons, one with ample water supply and one of severe drought. Using heated chambers, heat waves (3-day periods of high temperatures) were imposed at critical growth stages before anthesis (HT1) or post-anthesis (HT2, HT3). Gas exchange, chlorophyll content and concentration of nitrogen (N) in mainstem flag leaves, as well as concentrations of stem water-soluble carbohydrates (WSC) in mainstems were monitored throughout the season. Yield, biomass and thousand kernel weights (TKW) were measured at maturity. Elevated [CO2] moderated the effect on net CO2 assimilation rates of pre-anthesis (HT1), but not of post-anthesis heat waves (HT2, HT3). Growth under eCO2 increased stem WSC both, with and without experimental heat waves, but remobilisation decreased significantly under heat indicating that a greater WSC pool does not necessarily translate into greater remobilisation into the grain. Grain yield (g m−2) was greater under eCO2 and especially pre-anthesis heat stress decreased grain yield in the wetter season, and this decrease was stronger under eCO2 (up to 20%) than under aCO2 (up to 10%). Grain N decreased under eCO2, but less so under heat stress. We conclude that eCO2 may moderate some effects of heat stress in wheat but such effects strongly depend on seasonal conditions and timing of heat stress. © 2018 Elsevier B.V

The relationship between transpiration and nutrient uptake in wheat changes under elevated atmospheric CO2

Tausz, M ORCiD: 0000-0001-8205-8561The impact of elevated [CO2] (e[CO2]) on crops often includes a decrease in their nutrient concentrations where reduced transpiration-driven mass flow of nutrients has been suggested to play a role. We used two independent approaches, a free-air CO2 enrichment (FACE) experiment in the South Eastern wheat belt of Australia and a simulation study employing the agricultural production systems simulator (APSIM), to show that transpiration (mm) and nutrient uptake (g m−2) of nitrogen (N), potassium (K), sulfur (S), calcium (Ca), magnesium (Mg) and manganese (Mn) in wheat are correlated under e[CO2], but that nutrient uptake per unit water transpired is higher under e[CO2] than under ambient [CO2] (a[CO2]). This result suggests that transpiration-driven mass flow of nutrients contributes to decreases in nutrient concentrations under e[CO2], but cannot solely explain the overall decline. © 2017 Scandinavian Plant Physiology Societ