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The effect of auxin (IAA or 4-Cl-IAA) on the process of germination in lentil (Lens culinaris) was studied. The surface sterilized seeds were soaked in IAA (10-6 M) or 4-Cl-IAA (10 - 10 M, 10 - 8 M or 10 - 6 M) for 12 hours. The treated seeds were allowed to germinate in sterilized petri plate at 25 ± 2 0C in an incubator. The germinating seeds were sampled at 24, 48 and 72 h after germination to study the relative water content, rate of water uptake, mean daily germination, final germination percentage, level of protein and carbohydrate and the activity of nitrate reductase. The seedlings exhibited a linear increase in all the above parameters as the germination progressed. However, the varied concentrations of auxin differed from each other with respect to the degree of response. At the earliest stage (24 h) 10 - 6 M of 4-Cl-IAA was the most effective treatment. Whereas from 48 h onwards, 10 - -8 M of 4-Cl-IAA excelled in its effect and generated the best response. Overall, 4-Cl-IAA was superior to IAA in its effect.
Auxins constitute a small group of plant hormones, originally identified by their promotive
effect on bending)responses. IAA was the first natural auxin identified and now
it is widely considered to be the main auxin in plants that play a key role in the regulation
of plant growth and development (Davies, 2004). Some other naturally occurring auxins have
also been identified, which include 4-Cl-IAA, nephthyl acetic acid and indole-3-butyric acid.
4-Cl-IAA occurs in plants belonging to the family of Fabaceae (Engvild, 1994; and Reinecke,
1999) and also in the seeds of Pinus sylvestris stsen and Sandberg, 1986). A number
of bio-assays have demonstrated high degree of biological activities of 4-Cl-IAA such as the
growth of excised tissue, rooting and ethylene production in pea cuttings and the synthesis
of specific enzymes in detached cotyledons (Reinecke, 1999; and Ali et al., 2006a).
It also activates the rate of photosynthesis and seed production in Brassica juncea
(Ahmad et al., 2001a). Moreover, chlorosubstituted auxins are also known to increase the
activities of carbonic anhydrase in Brassica (Ahmad et al., 2001b) and -amylase in wheat
grains (Ahmad et al., 2001a), respectively. The response of chloroindole acetic acid varied
with the plant type (Reinecke et al., 1998). Therefore, the present study was carried out
to study the comparative effect of IAA and 4-Cl-IAA on carbohydrate, protein content, nitrate
reductase activity and water relations in the germinating seeds of lentil ( Lens culinaris).
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