Thiourea, also chemically named as Thiocarbamide, is a nitrogen and sulfur containing compound. It has three functional groups, amino, imino and thiol, each with important biological roles. Thiourea is being increasingly used to improve plant growth and productivity under normal and stressful conditions. Initially considered as growth stimulant in breaking bud dormancy and increasing crop yields, the thiourea is now known to have great roles in oxidative stress tolerance and modulation of gene expression and regulation and induction of signaling mechanisms[1].

Experiments

The study was conducted in sandy soil in plastic pots (38 cm and 24 cm). The TU dose (1000 mg/L) was pre-optimized and used in this study. Two canola varieties (G1?=?45S42 (heat tolerant) and G2?=?Hiola-401 (heat sensitive) was used independently in this study. The study comprised of two factors including (i) Growth conditions; NS?=?control-no stress (25/18 °C day/night) and HT?=?high temperature stress (35/25 °C day/night), (ii) TU supplementation; NA?=?control-no TU supplementation, WA1?=?water spray at seedling stage (Principal growth stage 3: Stem elongation, BBCH Scale-39), 39 days after sowing (DAS), TU1?=?foliage TU supplementation at seedling stage (Principal growth stage 3: Stem elongation, BBCH Scale-39), 39 DAS, WA2?=?water spray at anthesis stage (Principal growth stage 6: Flowering, BBCH Scale-60), 60 DAS, and TU2?=?foliage TU supplementation at anthesis stage (Principal growth stage 6: Flowering, BBCH Scale-60), 60 DAS. Thiourea, with a molecular weight of 76.12 g/mol, is also known by the alternate name thiocarbamide, according to the International Union of Pure and Applied Chemistry (IUPAC). To create the thiourea molecule, sulphur was added in place of oxygen in the urea molecule. Because of this substitution, thiourea's characteristics differed significantly from those of urea. At 25 °C, it dissolves in water sparingly, with a solubility of 142 g/L. The experiment comprised 60 pots, in two sets, each containing 30 pots; set-1 (45S42) and set-2 (Hiola-401). Following which, these two sets were further divided into 2 sets, the control containing 15 pots and the high temperature stress treatment consisting of other 15 pots.

The basic crop nutrition was delivered by applying modified Hoagland’s solution. The plastic pots (Length?=?38 cm and Width?=?30 cm) filled with 10 kg of sandy loam soil, were used for the seed sowing. Initially, ten seeds of both canola genotypes were sowed in each replicated pot. After emergence, only six plants/pots were kept for the data collection. Plants were raised at a normal temperature of 25/18 °C Day/night in two sets in two different growth rooms having the same internal conditions till anthesis (60 DAS), whereas in one growth room heat treatments were applied at 35/25 °C by maintaining the moisture level in each pot, 60% humidity, and 8 h light, 2 °C temperature increased on daily basis till it reached 35/25 °C. The internal conditions were controlled by the mechanized units of cooling, high temperature, humidifier/dehumidifier adjustment systems, and light (～12,000 lx). The temperature around crop canopies was recorded by digital maximum and minimum thermometers. The pot moisture content was maintained by adding water on a weight basis by using digital balance, as the number of grams decreased in pot weight was brought to the original weight (field capacity) by adding water.

Results

Figure 1. Thiourea applications (1000 mg/L) restored the plant physicochemical attributes, seed yield, seed oil content, and fatty acid profile in canola grown under heat stress (35 °C).

This study demonstrated that high temperature stress reduced canola growth, plant water status, seed yield, and yield quality in two genotypes; with more reduction in Hiola-401 compared with 45S42. High temperature stress triggered lipid peroxidation (malondialdehyde), accumulation of hydrogen peroxide, and electrolyte leakage, apparently by desynchronizing the mechanism of ROS-detoxification. Interestingly, thiourea supplementation restored high temperature-induced inhibitory effects on the canola development, physiology, seed yield, and seed oil content and seed oil quality; these favorable observations might primarily be attributed to lesser water loss, strengthened chlorophyll index, consistent leaf turgor, and greater availability of scavenging ROS amount. In addition, thiourea applications at anthesis improved the canola seed oil content and seed oil quality by increasing the amount of unsaturated fatty acids in two genotypes.[2]

References

[1] Thiourea: A Molecule with Immense Biological Significance in Plants. doi:10.5555/20193007055

[2] Thiourea improves yield and quality traits of Brassica napus L. by upregulating the antioxidant defense system under high temperature stress. doi:10.1038/s41598-024-62257-y