Crop residue position and interference with wheat seedling development
Unweathered crop residues can produce growth-inhibiting substances, stimulate pathogen growth, and immobilize nutrients. The location of seed relative to residue may be an important factor in the early health of a crop. This greenhouse study simulated sowing conditions possible under annual dryland winter wheat (Triticum aestivum L.) production to evaluate the likelihood of inhibitory effects. We placed newly harvested, unweathered winter wheat residue on the soil surface, mixed with the seed, immediately above the seed, or 3 cm below the seed. Treatments using a plastic residue substitute and treatments using pasteurized soil and residue provided comparisons to the natural soil and wheat residue. Residue mixed with or placed above the seed caused a temporary delay in emergence. Since this occurred with both wheat and plastic residue, the delay is explained by the physical impedance of coleoptile growth. Wheat residue 3 cm below the seed reduced the height and rate of wheat plant development, indicating a biological inhibitory effect of the wheat residue. This reduction in height and development rate at 20 days after planting did not occur when the soil and residue were pasteurized. We conclude that winter wheat seedling growth can be inhibited if roots encounter unweathered residues. [1]
Relative Date of Wheat Seedling Emergence and Its Impact on Grain Yield
Emergence of wheat (Triticum aestivum L.) seedlings usually occurs over a period of several days, resulting in nonuniformity among neighboring plants. The impact of nonuniformity in time of emergence on grain yield has not been determined. We determined effect of planting depth on relative date of seedling emergence, and of relative date of emergence on grain-bearing tillers and grain yield per plant. Large seed (39.8 ± 4.59 mg kernel−1) in 1989, and large (41.7 ± 3.83 mg kernel−1) and small seeds (24.3 ± 4.56 mg kernel−1) in 1990 were obtained from ‘Roblin’ wheat. Seeds were hand.planted at 25-, 50-, and 75-mm depths on Neuborst clay loam (fine-loamy, frigid, Aquic Haploborolls) at Portage la Prairie, MB. Plants were tagged the day they emerged, and individual plant yield was determined at harvest. Planting depths did not differ for total percent emergence in 1989, but in 1990, increasing planting depth led to decreased total emergence. Gompertz growth model predictions of inflection time, maximum emergence rate, and cumulative percent emergence indicated that seedling emergence rate decreased as planting depth increased, and the decrease was greater with small seed than with large seed. The first date on which seedlings emerged each year was designated as Day 1. Averaged across 2 yr, plants that emerged on Day 1 to 3 produced 1.4 times the yield of those emerged on Day 4 to 6, and 3.2 times the yield of those emerged on Day 7 to 9. Reduced yield of late emerged plants was due primarily to fewer grain-bearing tillers. This research demonstrates the benefit of shallow placement of large seeds in minimizing variation in time of seedling emergence among plants, and increasing grain yield. [2]
Winter Wheat Seedling Emergence from Deep Sowing Depths
Growers in low-precipitation (<300 mm annual) dryland wheat-fallow areas of the inland Pacific Northwest need winter wheat (Triticum aestivum L.) cultivars that emerge from deep sowing depths in dry soils. Stand establishment is the most important factor affecting winter wheat grain yield in this region. Despite poor resistance to disease, modest grain yield potential, and other problems, the outdated soft white winter wheat (SWWW) cultivar Moro is widely sown in these dry areas, due to its excellent emergence ability. All other SWWW cultivars are semidwarfs that carry emergence-impeding Rht1 or Rht2 reduced-height genes. From 12 sowing trials at 2 locations over 4 yr, we compared the emergence capability of Moro to (i) 8 SWWW cultivars and (ii) 16 SWWW advanced experimental Mororeplacement lines. Under both wet and dry soil conditions (soil water content in the seed zone ranged from 11 to 19 mm3 mm−3), seeds were sown deep, with 110 to 160 mm of soil cover. Moro always emerged fastest and achieved the best final stand compared with the semidwarf cultivars. The advanced experimental lines, which contained either no reduced-height gene or a Rht1, Rht2, or Rht8 reduced-height gene, had superior straw strength, disease resistance, and grain quality compared with Moro. The best-emerging advanced experimental lines had coleoptile lengths >100 mm. Coleoptile length was associated with emergence capability among both cultivars (r2 = 0.71, P < 0.004) and advanced lines (r2 = 0.62, P < 0.001). From deep sowing depths in this study: (i) cultivars and advanced lines with Rht1 and Rht2 reduced-height genes always emerged poorly compared with Moro; (ii) the Rht8 reduced-height gene did not hamper emergence to the extent that Rht1 and Rht2 did; and (iii) several advanced experimental lines with long coleoptiles equaled or exceeded Moro for emergence. [3]
Assessment of Concentrations of Nano and Bulk Iron Oxide Particles on Early Growth of Wheat (Triticum aestivum L.)
Aims: In this work we assessed Fe2O3 nanoparticles with bulk Fe2O3 for possible phytotoxicity and stimulative effects on wheat seed germination and early growth stage.
Methodology: The treatments in the experiment were five concentrations of bulk (100, 500, 1000, 5000 and 10000 ppm) and five concentrations of nanosized Fe2O3 (100, 500, 1000, 5000 and 10000 ppm) and an untreated control. Germination tests were performed according to the rule issued by ISTA. Analysis of variance (ANOVA) was performed between treatment samples. The information was analyzed using MSTAT-C computer software. Means compared by multiple range Duncan test and a 95% significance level (p < 0.05) was employed for all comparisons.
Results: Results showed that exposure of seeds to 100 ppm iron oxide nanoparticles indicated the greatest germination rate (by 41% more than control group) related to other treatments. Increasing nanoparticles concentration above 100 ppm reduced seed germination rate. It has not found any significant effects by bulk and nanoparticles on elongation of shoot, root and seedling of wheat. Application of 100 ppm concentration of nanosized Fe2O3 reduced mean germination time (MGT) by 38.5% in comparison to the control, while 100 ppm concentration of bulk Fe2O3 did not decrease MGT in comparison with the control. The highest root biomass was achieved from concentration of 100 ppm nano- Fe2O3, but an increased concentrations of nanoparticles Fe2O3 significantly reduced root weight. Nevertheless, on the basis of these results it is highly recommended that the influence of low dose nanomaterial be assessed in order to encourage seed germination and seedling growth. [4]
Effect of Gravity Variation on the Growth of Wheat and Guinea Corn Seedlings
In this study, the impact of gravity on plant growths was studied to determine the orientation of the roots and shoots under simulated microgravity using the clinostat. The experiment was performed with two local seeds-wheat (Triticum aestivum) and guinea corn (Sorghum bicolor).
The agar-agar solution prepared was evenly distributed into the petri dishes where nine seeds each of wheat and guinea corn was planted on four petri dishes. The petri dishes containing the seeds were cultivated in the wet chamber for about 20-30 hours. Three petri dishes were selected in the following order, 1g, 90o turned and clinorotated samples respectively. Five readings were taking at thirty minutes interval.
Data on plants growth were collected from photographs taken during the course of the experiments and analyzed using Image J software to measure the root curvature and growth rate.
The results show that the wheat has the longest root of about 4.2 cm at 90 minutes and Guinea corn 2.58 cm at 120 minutes. The growth rate of clinorotated wheat is 1.88 times that of guinea corn at 90 minutes while that of 1g remained the same. The speed of clinorotation did not affect growth of clinorotated wheat and guinea corn but growth rate of guinea corn was about 23% lower than wheat. The higher value of angle indicates a more pronounced curvature of the root therefore; wheat germinates faster than guinea corn in simulated microgravity. .[5]
Reference
[1] Wuest, S.B., Albrecht, S.L. and Skirvin, K.W., 2000. Crop residue position and interference with wheat seedling development. Soil and Tillage Research, 55(3-4), pp.175-182.
[2] Gan, Y., Stobbe, E.H. and Moes, J., 1992. Relative date of wheat seedling emergence and its impact on grain yield. Crop Science, 32(5), pp.1275-1281.
[3] Schillinger, W.F., Donaldson, E., Allan, R.E. and Jones, S.S., 1998. Winter wheat seedling emergence from deep sowing depths. Agronomy Journal, 90(5), pp.582-586.
[4] Feizi, H., Moghaddam, P.R., Shahtahmassebi, N. and Fotovat, A., 2013. Assessment of concentrations of nano and bulk iron oxide particles on early growth of wheat (Triticum aestivum L.). Annual Research & Review in Biology, pp.752-761.
[5] Aluko, O.E. and Onabowale, M.K., 2019. Effect of Gravity Variation on the Growth of Wheat and Guinea Corn Seedlings. Journal of Experimental Agriculture International, pp.1-9.
