The goal of the present work was to investigate the influence of laser irradiation Invitor on growth, anatomy, flowering, chemicals composition, and gene mutagenesis.
According to data presented in vitro growth ability, we can notice that most of laser types (green, blue, and red laser radiation) for any exposure times (5, 10, and 25 min) led to increase in shoot multiplication of Eustoma grandiflorum except for blue laser radiation for 5 min when compared with control (1.22). The data go in line with those obtained by Danaila et al. (2011) on Petunia hybrid and Dianthus caryophyllus plants and Hwida et al. (2012) on Balanites aegyptiaca and Cotoneaster horizontalis. Lobna et al. (2014), Rania et al. (2015), and Hwida et al. (2012) mentioned that the maximum shootlets number per explant of Balanites aegyptiaca were observed with red laser treatments. Therefore, the mechanism influence of laser irradiation is most likely attributed to light and electromagnetism effects. Longest shootlets were produced from exposing Eustoma grandiflorum shootlets to green and blue laser for short time exposure 5 min produced as well as long time exposure of red laser (20 min) as compared to control. These results were in agreement with Lobna et al. (2014), Sahar et al. (2014), and Ali et al. (2014). The cell elongation resulted by laser treatments increased gibberellic acid which increased the cell vacuoles (Mahmoud and brahem 2000).
The highest number of leaves per shootlet appeared with red laser for 5 min as compared to control. These results were confirmed by researchers such as Danaila et al. (2011), Hwida et al. (2012) Lobna et al. (2014), and Rania et al. (2015). Using He-Ne laser beam stimulation related to higher activity of some enzymes in treated biological material Dobrowolski et al. (1987).
All laser radiation treatments had not significant effect on rooting percentage of Eustoma grandiflorum plant as compared to control. Some studies similar with our study like Hanna and Babelewski (2014)mentioned that the laser radiation did not affect percentage of rooted cutting. This was due to the first reason type and concentration of auxin.
The highest number of roots was obtained with blue laser for 5 min. However, the minimum of root/shootlet was observed with red laser for 25 min as compared to control. These results were confirmed by Hwida et al. (2012), Metwally et al. (2013) and Rimal et al. (2014).
Regarding the effect of laser radiation on length of roots as affected by different types of laser radiation and various times exposure, data showed that the longest roots were resulted from irradiation of shoots with green laser for 10 min as compared to control. Our study was confirmed by Lobna et al. (2014), Hwida et al. (2012), and Metwally et al. (2013).
In this investigation, results in acclimatization stage also showed that the best results for the number of branches per plant were obtained from the green laser for the long time exposure (25 min) and red laser for short time exposure (5 min). These results similar to Osman et al. (2009) and Aguilar et al. (2015) reported that laser radiation could cause enhancement of enzyme activity. Also may be the endogenous content of GA and role in cell elongation, where GA may cause cell elongation by induction of enzymes that weaken the cell wall (Macleod and Millar 1962).
The tallest branches were resulted from different types of laser radiation such as green, blue, and red for various times (10, 5, and 20 min, respectively) as compared to control. Our study agree with (Aladjadjiyan 2002) who mentioned that the He-Ne laser irradiation could raise the activities of superoxide dismutase (SOD) and Ascorbate peroxidase (Apx) enzymes in plants which resulted in accelerating the plant physiological metabolism and increased plant growth.
The highest number of leaves per branch was resulted with green laser for 25 min as compared to control. Osman et al. (2009) found that the best number of leaves and number of branches produced from application of laser treatments for 20 min for both seasons. Noha and El Ghandoor (2011) expressed the stimulated seedling length, average number of leaves for longer treatment time with laser application for 30–120 min. The highest leaf area was resulted from using green light of laser for 20 min compared to control and other treatments. These results were confirmed by some researchers such as Rybiñski and Garczyñski (2004), Al-sherbini et al. (2015), and El-Kereti et al. (2013) who revealed that the increase in leaf area may be reflected by the effect of rays on cell division which continues to all parts of plant at vegetative stage or may be the main biological active gibberellic acid formation is promoted by laser radiation.
It is evident from our result that red laser radiation for 5 min delayed bud flower initiation. The longest period was resulted from red light laser treatments for 5 min. Contrary, the shortest was obtained with blue light of laser for 20 min. These results were agreed with Podleoeny (2002) and Metwally et al. (2013).
Considering the flowering percentage of Eustoma grandiflorum plant, results showed that among different treatments, shootlets exposure to blue and red light laser radiation for 20 min gave the best results of flowering percentage and flower diameter compared to control and other treatments.
The highest number of flower buds per plant and the highest number of flowers per plant were resulted with blue laser radiation for 20 min. These finding were in agreement with El-Tobgy et al. (2009) and Osman et al. (2009).
The longest bloom stem length and fresh weight of flower were obtained with 20 min of blue light of laser radiation as while the shortest bloom stem length and fresh weight of flower was obtained with 5 min of red light of laser radiation as compared to control.
The longest peduncle length was obtained with 25 min red light laser radiation as compared to control while the shortest peduncle was observed with 5 min and 10 min of red light laser radiation. The peduncle length was increased gradually with increasing time exposure times.
The treated shootlets with 20 min of blue light laser radiation delayed the flower senescence to 12.67 day and recorded the highest petal area as compared to control these results online with Metwally et al. (2013) and Ritambhara and Girjesh (2013). While the maximum number of petals were observed with 20 min of green light and 25 min of red light laser radiation as compared to control.
The maximum number of stamens was recorded with 10 min of green laser. Mohammed (2005) found that irradiated Salvia officinalis plant with different doses and time exposure of He-Ne laser produced higher yield of herb compared to other types of laser. While the best results of dry weight also was observed with 25 min of each of blue and red light of laser rays comparing with control and other treatments. These results were agreed with Sahar et al. (2014).
Data presented indicated that shootlets were irradiated with short exposure time of green laser radiation resulted the best results for pigments content as compared to control and other treatments. The maximum values of chlorophyll (a, b), carotenoids, and total chlorophyll (a + b) were resulted from green light of laser for 5 min as compared with control. Our results were agreed with some researchers such as Lobna et al. (2014) Al-sherbini et al. (2015), Rania et al. (2015), and Dziwulska et al. (2016).
Our data indicated that anthocyanin content of Eustoma grandiflorum petals were significantly increased by using dose of laser radiation and reached up to maximum values with both doses (green for 20 min and red light laser for 25 min) as compared to control. Kurata et al. (2000) found that blue and red laser radiation was able to stimulate anthocyanin production.
The results presented indicated that the highest thickness of midvein, thickness of lamina, number of xylem rows, number of vessels, and diminution of vascular bundle (length − wide) were obtained with 20 min cadmium and 25 min helium neon laser as compared with control and other treatments. The results were mentioned by Hwida et al. (2012) and Bedour et al. (2012).
In general, the plant growth is associated with some factors such as enzymes and hormones like cytokinin and gibberellic acid (GA3). The primary study observed that the red light of laser radiation have important role on GA3 formation and the endogenous content of GA1 according to Kamiya and Martinez (1999). The GA3 response for cell elongation and other effects such as weaken the cell wall, production of proteolytic enzymes, increase of auxin content, increase of concentration of sugar, raising the osmotic pressure in cell soap. This elongation of cell which is treated with laser radiation led to increase of plant height, number of branches, and number of flower according to Lobna et al. (2014) and Rania et al. (2015), Using of laser radiation increased the nitrogen content that caused increase in protein content which is necessary for increasing plant organs such as branches and number of umbels (Osman et al. 2009). According to Mahmoud and Brahem (2000), they indicated that the cell number increased by laser radiation that increased nucleic acids and phospholipids membranes as well as increased phosphorus and potassium contents that led to cell elongation irradiated with laser radiation.