Abstract
Strigolactones (SLs) are newly identified unique class of sesquiterpenoid phytohormones. Their role in seed germination and seedling growth and development is yet to be elucidated. As we know that the germination of seed is critical phase in a plant's life cycle. Therefore, the present experiment aimed to study the function of strigolactone (GR24) in the regulation of physiological and biochemical mechanisms related to seed germination, and the growth and development of five tomato genotypes viz. Crystal Select (V1), Super Strain-B (V2), Riogrand (V3), Tomate Tres Cantos (V4) and Tomato Strain-8 (V5). In the present studies, we conducted two experiment (1) Petri dish experiment for the study of germination attributes and (2) pot experiment for growth and physio-biochemical study. Different concentrations of SL were directly supplied to the Petri dishes for seed germination. Basal doses of SL were supplied to seedlings grown in pots. Increasing levels of SL triggered the germination potential of all genotypes of tomato by increasing the activity of alpha-amylase (alpha-A) activity and protease (Ptase). The concertation of 0.20 mu M of SL increased alpha-A activity, Ptase activity, germination %, germination index, vigor index by 54.54%, 53.82%, 21.63%, 60.31% and 302.39%, respectively, as compared to respective controls. Among the treatments and genotypes, 0.20 mu M of SL and cultivar V3 proved best by producing maximum values for these attributes. Similarly, increasing levels of SL increased growth parameters (shoot and root length, shoot and root fresh weight, and shoot and root dry weight) and physio-biochemical characteristics [Chlorophyll (Chl) a and b, net photosynthetic rate, stomatal conductance, internal CO2 concertation, carbonic anhydrase activity, proline (Pro) and total soluble carbohydrates (TSC) content, and activity of pyrroline-5-carboxylate synthase, nitrate reductase, nitrite reductase]. It may be concluded that exogenous SL improved germination potential by stimulating alpha-A activity and Ptase, and plant growth and development by increasing biosynthesis of Chl, Pro and TSC, photosynthesis process, and nitrogen assimilation.