INTRODUCTION:

Indian indigo (Indigofera tinctoria) commonly known as king of dyes is a deciduous sub shrub of the south eastern Asia. It belongs to the bean family or Fabaceae. The shoots of the plant contain indigotin, which is the source for a deep blue dye. Indigo is not found as a native compound in plants, but as a product of a secondary metabolite named indoxyl. This metabolite is present in most of the indigo-producing plants as indican (indoxyl--d-glucoside). These plant derived dyes are useful in dyeing cloths which do not produce dermatitis (Gulrajani and Gupta, 1992). Indigo is the oldest blue dye utilized by man and was commercially much exploited till synthetic colouring material was evolved. The plant besides utilized as a source of blue dye is also valued in ayurveda as an important ingredient of hair tonics like Neelibhringadi thailam. It is used in the treatment of myelocytic leukemia (Aobchey et al., 2007). It is also useful in treatment of inflammatory skin conditions and treatment of tonsils. The plant has hepatoprotective activity (Singh et al., 2001) and antidyslipidemic activity (Narender et al., 2006). An infusion of roots is given as an antidote in case of snake bite poisoning. The plant has significant importance as a potential green manure crop also. (Garrity et al., 1994)

I. tinctoria is the earliest known source of indigo. It is a biennial and mainly outbreeding species, probably indigenous to southeastern Asia. I. tinctoria seedlings form a rosette of leaves in the first year of their cycle, and an erect stem bearing yellow flowers on short racemes in the following spring.

METHODS AND MATERIALS:

Indigofera plant is a leguminous wild variety yields dye and also possess medicinal potential to cure several diseases as used in tribal populations.

Hence the germination of the seeds is difficult in natural conditions. To efficiently cultivate a species, the seeds must be viable and active for germination. Cultivation using active seeds, or seeds released from dormancy, allows uniform germination, emergence, and optimal stand for establishment. Scarification of an impermeable seedcoat allows physically dormant seed to imbibe water and subsequently germinate (Jones et al., 2016). A number of scarification methods have been found to overcome physical dormancy. In this study, an experiment was planned to determine the efficient method of seed germination in Indigofera tinctoria.

RESULTS AND OBSERVATIONS:

Indigofera can be grown as an annual, biennial or perennial plant. The seeds of the plant are small and possess a very hard seed coat (Fig. 1).

Fig. 1: Seeds and Pods of Indigofera tinctoria

The seeds were subjected to thermal, mechanical or chemical scarification. Thermal scarification involves subjecting the pre sown seeds at particular temperature for fixed time. The different thermal scarification treatments and the germination percentage of the seeds are enlisted in Table 1.

Table 1: Thermal scarification, treatments and percentage germination

Treatments	Temperature	Time (hours)	Germination (%)
T1	40⁰C	2,4,6,12,24	4,8,8,9,11
T2	60⁰C	2,4,6,12,24	9,10,14,15,16
T3	80⁰C	2,4,6,12,24	10,12,29,24,18
T4	100⁰C	2,4,6,12,24	15,18,13,5,3

The treatments for mechanical scarification involve sanding, grinding and both. The seed germination obtained with mechanical scarification is shown in Table 2.

Table 2: Mechanical scarification, treatments and percent germination

Treatments	Germination (%)
Sanding	3
Grinding	5
Sanding+Grinding	10

In chemical scarification, the seeds are subjected to sulphuric acid treatment at varying concentration for fixed amount of time (Table 3).

Treatments	Sulfuric acid (%)	Time (Min)	Germination (%)
T1	10	Quick,1, 5,10,30,60	1,2,3,5,18,21
T2	25	Quick,1,5,10,30,60	2,3,8,13,15,20
T3	50	Quick, 1,5,10,30,60	5,6,7,12,34,28
T4	75	Quick,1,5,10,30,60	17,23,30,61,2,1
T5	100	Quick,1,5,10,30,60	76,18,1,0,0,0

The treatments were carried out in four replications with 100 seeds per replication. The percentage of total number of seeds germinated per treatment was calculated. The results from this study show that a quick dip in 100% concentrated sulfuric acid was the best scarification treatment for seed germination in Indigofera tinctoria. By this treatment 76% of the seeds germinated. The maximum and minimum germination percentage obtained from different scarification treatments are depicted in Fig. 2.

Figure 2: Maximum and minimum germination percentage in various scarifications

The best treatment for thermal scarification was subjecting the seedlings to 80°C for 6 hours, which gave a germination percentage of 28. For thermal scarification the germination percentage varied from 2-28%. The best mechanical scarification treatment was a combination of sanding and grinding, which provided a germination percentage of 10.

REFERENCES:

1. Aobchey P, Sinchaikul S, Phutrakul S and Chen ST (2007): Simple purification of indirubin from Indigofera tinctoria (L). and inhibitory effect on MCF-7 human breast cancer cells. Chiang Mai Journal of Science 34(3): 329-337

2. Garrity DP, Bantilan RT, Bantilan CC, Tin P and Mann R (1994): Indigofera tinctoria: Farmer-proven green manure for rainfed ricelands. In Greenmanure production systems for Asian rice lands: selected papers from the International Rice Research Conference. Los Baños (Philippines): International Rice Research Institute. p (pp. 67-81).

3. Gulrajani ML and Gupta D (1992): Natural dyes and their application to textiles, Department of Textile Technology, Indian Institute of Technology.

4. Jones CD, Stevens MR, Jolley VD, Hopkins BG, Jensen SL, Turner D and Stettler JM (2016): Evaluation of thermal, chemical, and mechanical seed scarification methods for 4 Great Basin lupine species. Native Plants Journal 17(1): 5-18.

5. Narender T, Khaliq T and Puri A (2006): Antidyslipidemic activity of furanoflavonoids isolated from Indigofera tinctoria. Bioorganic and Medicinal Chemistry Letters, 16(13): 3411-3414.

6. Singh B, Saxena AK, Chandan BK, Bhardwaj V, Gupta VN, Suri OP and Handa SS (2001): Hepatoprotective activity of indigtone—a bioactive fraction from Indigofera tinctoria Linn. Phytotherapy Research, 15: 294-297.

Received on 15.11.2020 Modified on 23.11.2020

Research J. Science and Tech. 2020; 12(4):311-313.

DOI: 10.5958/2349-2988.2020.00045.5