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contain a number of active compounds that can be practiced for various therapeutic purposes

or for the production of several precious medicines. Silybum marianum (L.) Gaertn., also
known as Milk thistle and belongs to family Asteraceae. It is mainly recognized as a

medicinal plant from earlier times (Kren and Walterova, 2005; Khan et al., 2009). This plant
is indigenous to the Mediterranean and North African countries and is now cultivated in

many other countries also (Boulos, 2000). Silybum marianum is a winter season crop and can
grow in dry regions, stony and swampy areas, fields and along roadsides. Approximately 8 to

33% of populations which are suffering from liver disorders consume this plant globally

(Polyak et al., 2007).
The optimal functioning of plants is altered by many endogenous and exogenous assets.

Among the endogenous aspects, PGRs helpful in influencing various biological processes of

plants. PGRs influence various activities and development of plants at very low
concentrations, while they inhibit it at high concentrations. PGRs also helpful in providing

plant tolerance to abiotic stresses for instance drought, salinity, heavy metal and osmotic
stress (Vardhini and Rao, 2003). The plant reply to PGRs may differ with plant varieties, age

of plant, environmental circumstances, physiological status, mineral nutrition, phase of
development and internal hormone balance (Aftab et al., 2010). PGRs have impact on plant’s

morphological, physiological and biochemical aspects. Auxins are identified for their

function in cell elongation, differentiation, cell division, apical dominance, leaf expansion
and prevents abscission. IAA is one of the naturally occurring auxin which functions in

improving stem elongation, cell expansion and growth rate (Arif et al., 2001). Hence PGRs
i.e., auxins are beneficial compounds which are helpful in improving various plant metabolic

progressions to boost plant growth and development (Hadi et al. 2010).

MATERIALS AND METHODS
Experimental Set Up and Growth Parameters

Seeds of S. marianum were procured from University of Horticulture and Forestry,
Nauni, Solan, Himachal Pradesh. Seeds of S. marianum were sown in plastic pots (21 cm

diameter and 19 cm height) which were filled with 5 kg mixture of air-dried local soil

(alluvial texture) and organic manure. Leaves and stem of plants were sprayed with solutions
of IAA at 25, 50 and 100 ppm concentrations. Twenty ml of the various concentrations were

sprayed on each plant after 10 days interval, using a hand sprayer. Triplicates were used for
each concentration. Control plants were sprayed with distilled water. Sampling was done

three times i.e. after 20, 40 and 60 days of spraying.

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