Germination is a key process in plants' phenological cycles. Accelerating this process could lead to improvment of the seedling growth as well as the cultivation efficiency. To achieve this, the effect of microwave frequency on the germination of rice seeds was examined. The physiological feedbacks of the MR 219 rice variety in terms of seed germination rate (GR), germination percentage (GP), and mean germination time (MGT) were analyzed by exposing its seeds to 2450 MHz of microwave frequency for one, four, seven, and ten hours. It was revealed that exposing the seeds to the microwave frequency for 10 hours resulted in the highest GP. This treatment led to 100% of germination after three days with a mean germination time of 2.1 days. Although the other exposure times of microwave frequency caused the moderate effects on germination with a GP(a3) ranged from 93% to 98%, they failed to reduce the MGT(a3). The results showed that ten-hour exposure times of microwave frequency for six days significantly facilitated and improved the germination indices (primary shoot and root length). Therefore, the technique is expected to benefit the improvement of rice seed germination considering its simplicity and efficacy in increasing the germination percentage and rate as well as the primary shoot and root length without causing any environmental toxicity.
Photobiomodulation relies on the transfer of energy from incident photons to a cell photoacceptor. For many years the concept of photobiomodulation and its outcome has been based upon a belief that the sole receptor within the cell was the mitochondrion. Recently, it has become apparent that there are other photoacceptors operating in different regions of the electromagnetic spectrum. Alternative photoacceptors would appear to be water and mechanisms regulating calcium homeostasis, despite a direct effect of laser photonic energy on intracellular calcium concentration outwith mitochondrial activity or influence, have not been clearly demonstrated. Therefore, to increase the knowledge of intracellular‑calcium and laser photon interaction, as well as to demonstrate differences in irradiation profiles with modern hand-pieces, we tested and compared the photobiomodulatory effect of 808 nm and 980 nm diode laser light by low- and higher-energy (60s, 100 mW/cm2, 100 mW/cm2, 500 mW/cm2, 1000 mW/cm2, 1500 mW/cm2, 2000 mW/cm2) irradiated with a "standard" (Gaussian fluence distribution) hand-piece or with a "flat-top" (uniform fluence) hand-piece. For this purpose, we used the eukaryote unicellular-model Dictyostelium discoideum. The 808 nm and 980 nm infrared laser light, at the energy tested directly affect the stored Ca2+ homeostasis, independent of the mitochondrial respiratory chain activities. From an organism perspective, the effect on Ca2+-dependent signal transduction as the regulator of spore germination in Dictyostelium, demonstrates how a cell can respond quickly to the correct laser photonic stimulus through a different cellular pathway than the known light-chromophore(mitochondria) interaction. Additionally, both hand-piece designs tested were able to photobiomodulate the D. discoideum cell; however, the hand-piece with a flat-top profile, through uniform fluence levels allows more effective and reproducible effects.
The exposure of plant seeds to gamma radiation is a promising prospect to crop improvement through the manipulation of their genetic makeup. Previous studies have shed light on the potential of radiation to enhance the genetic variability. In this study, we investigated the effect of gamma radiation on Pisum sativum seeds under heavy metal (nickel chloride) stress to determine the changes in morpho-biochemical attributes. Morphological parameters such as germination and photosynthetic pigments while biochemical attributes such as protein content, sugar, phenolics, and flavonoids were determined. The results showed that gamma radiation, along with (NiCl2) has a pronounced effect on plant morphology and production. In the biochemical analysis of the range from 50 Gy to 100 Gy, photosynthetic pigments and proteins were significantly associated. Although the 50 Gy dose induced a partial reduction in sugar content while the 100 Gy dose demonstrated a slight improvement relative to the 50 Gy dose. However, the phenol content increased in response to 50 Gy, whereas the flavonoid content decreased compared to the control. In combination with heavy metal (50mM) at Gy doses, the protein, sugar, phenol, and flavonoid contents showed a gradual decrease with the increase in Gy doses. In conclusion, the current study based on observations suggests that the range of gamma radiation from 50 Gy to 100 Gy is suitable for causing the mutant form of seeds. However, further studies should be conducted to determine the precise mechanism, in order to be benefitted from full potential role of gamma radiation in improving productivity under heavy metal stress.