Effects of Different Silicon Source Treatment on Rice Seedlings 2018-09

Effects of Different Silicon Source Treatment on Rice Seedlings 2018-09

Effects of Different Silicon Source Treatment on Rice Seedlings
National Pingtung University of Science and Technology Department of Plant Industry

1. Introduction
Rice (Oryza sativa L.) belongs to the Poaceae (Gramineae) family Monocotyledonous plants prefer a warm and rainy climate. Taiwan is located in a tropical and subtropical climate zone, with abundant rainfall and high temperature, which is suitable for rice growth. Taiwan can grow two seasons of rice a year. It is the industry with the widest planting area and the largest number of farmers. It is the most important crop in Taiwan. Rice contains 72-79% of carbohydrates, it is the largest source of calories for human beings, it also consists of 7.0-9.0% plant protein, 0.6-2.5% fat, 0.1-2.0% dietary fiber, and 0.4% ~1.0% ash and is rich in minerals, B vitamins and etc. Rice has considerable benefits for humans.

Silicon (Si) is an essential mineral nutrient element for plant growth and development. It plays an important role in plants. The application of silicon fertilizer can form a cuticle-silicon double layer under the epidermal tissue, which can significantly improve rice lodging resistance. During rice growth, silicon fertilizer can make the extension angle of rice leaves smaller and the leaves stand upright to improve the photosynthetic efficiency. In addition, silicon may form complexes with organic compounds in the epidermal cell wall, thereby increasing its resistance to enzymatic degradation. Therefore, in this experiment, rice seedlings were treated with three types of silicon sources, including silicon dioxide (liquid), silicon dioxide (colloidal), and potassium silicate, to understand the effects of different silicon sources on rice growth and antioxidant activity.

2. Material method
In this experiment, rice was cultivated by hydroponics, and Kaohsiung No. 145 was selected as the experimental variety. All silicon source materials were provided by DIAMOND QUANTUM BIOTECH CO., LTD.  At the beginning of the experiment, the optimal treatment concentration of rice treated with different silicon sources was discussed. In the experiment, about 20 germinated rice seeds were placed in each hydroponic cup, and then transferred to the growth chamber for one week before adding different concentrations of silicon to the hydroponic solution. After confirming the optimal treatment concentration of each silicon source, the rice was treated with the optimal concentration. The chlorophyll content was analyzed. Antioxidant enzyme activity was also analyzed, including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR). Each of the above treatments was performed in quadruplicate. The data of this experiment were tested via Analysis of Variance (ANOVA) and Least Significance Difference (LSD).

3. Results
1. Analysis of growth traits of rice seedlings treated with different silicon source
The rice was treated with different silicon sources after one week of growth in the growth chamber. The treatment concentrations were: 

(a) Liquid silica (Liq): 0x, 1,000x, 1,500x and 2,000x. 
(b) Colloidal silica (Col): 0x, 800x, 1,000x and 1,500x. 
(c) Potassium silicate (PS): 0x, 1,000x, 1,500x and 2,000x. 

From the table below (Table 1), it can be seen that the optimum concentration of each silicon source is: liquid silica 1,000x, colloidal silica 1,000x, and potassium silicate 1,500x. In this experiment, it can be found that in terms of plant height, liquid silica and potassium silicate have better effects, followed by colloidal silica. In terms of dry weight above ground, potassium silicate is higher; in terms of dry weight for underground parts, the effect of silica is better than that of potassium silicate, and the effect of colloidal silica is better.

Table 1. Effects of different silicon source concentration treatments on rice agronomic traits

Silicon source  Concentration Plant height (cm) Root length (cm)  Above ground Underground
Fresh weight (g)    Dry weight (g) Fresh weight (g)    Dry weight (g)
Liquid silica 0x 19.28 ABa 13.64 Aa 0.572 0.0909 0.05 0.0347
1,000x 19.77 ABa 13.15 Aa 0.6086 0.0964 0.046 0.0363
1,500x 18.95 ABa 12.89 .Aa 0.5214 0.0891 0.0369 0.0314
2,000x 19.13 ABa 12.76 Ab 0.5332 0.0925 0.0435 0.0357
Colloidal silica 0X 18.3 Bb 12.36 Aa 0.5472 0.0946 0.0726 0.037
800x 17.53 Bc 12.62 Aa 0.5283 0.0895 0.0836 0.0414
1,000x 19.06 Ba 12.16 Aa 0.6097 0.1034 0.1164 0.0449
1,500x 18.99 Ba 12.34 Aa 0.5957 0.0962 0.0878 0.0396
Potassium silicate 0x 19.8 Ad 11.47 Ba 0.5894 0.0839 0.067 0.0377
1,000x 20.44 Ac 9.65 Ba 0.5854 0.0982 0.0412 0.0285
1,500x 21.52 Ab 10.04 Ba 0.6667 0.1106 0.0589 0.0325
2,000x 22.10 Aa 9.46 Ba 0.6513 0.1157 0.0329 0.0285
Uppercase letters indicate differences among treatments with different silicon sources; lowercase letters indicate differences among treatments with different concentrations of the same silicon source. Different letters indicate significant differences between treatments (P ≤ 0.05).
 
Observing the appearance of rice seedlings with the optimum concentration of different silicon sources, there was no significant difference in appearance between each treatment (Fig. 1), indicating that different silicon sources did not affect the growth of rice seedlings after treatment.
Figure 1. Effects of different silicon sources on the growth of rice seedlings.
After one week of rice growth, untreated (a), liquid silica 1,000x (b), colloidal silica 1,000x (c), and potassium silicate 1,500x (d).

 

2. Effects of different silicon sources on chlorophyll in rice
When the rice grew to three-leaf stage, 90-100 mg of rice leaves from each treatment were used for the determination of chlorophyll content, and four replicates were performed. From the research results in Table 2, it can be seen that there is no significant difference in chlorophyll content between each silicon source treatment and the control group, indicating that different silicon source treatments will not have a negative impact on rice physiology.

Table 2. Effects of different silicon source treatments on chlorophyll in rice seedlings
Silicon source Concentration Chlorophyll a content Chlorophyll b content Total chlorophyll
content
Control group 0x 1.62±0.15a 0.43±0.05a 2.05±0.20a
Liquid silica 1,000x 1.61±0.10a 0.42±0.03a 2.03±0.13a
Colloidal silica 1,000x  1.53±0.06a 0.40±0.02a 1.93±0.08a
Potassium silicate 1,500x 1.42±0.18a 0.37±0.05a 1.79±0.23a

Different letters indicate differences in treatment (P ≤ 0.05)

3. Effects of different silicon source treatments on the activities of antioxidant enzymes in rice seedlings
The rice was treated with the optimum concentration of different silicon sources, and the activity of antioxidant enzymes was analyzed. The results showed that there was no significant difference in SOD activity and CAT activity compared with the control group. However, in terms of APX activity performance, all rice seedlings treated with silicon source decreased APX activity, but in terms of GR activity performance, colloidal silica treatment showed a higher trend (Fig. 2).

Figure 2. Effects of different silicon source treatments on the activities of antioxidant enzymes SOD (a), CAT (b), APX (c), and GR (d) in rice seedlings.

4. Conclusion
Based on the above results, after the rice seedlings were treated with different silicon sources, 1,000x liquid silica, 1,000x colloidal silica, and 1,500x potassium silicate were the optimal treatment concentrations. In terms of activity change, the effect of silica treatment is better than that of potassium silicate, among which colloidal silica can increase the dry weight underground and increase the trend of GR activity. The test results can be used as a reference for farmers when choosing silicon fertilizers.

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