Improvement of Micropropagation and Proliferation of Robinia pseudoacasia L. Using Plant Growth Regulators and Extracts of Brown Seaweed Ascophyllum nodosum

The present study was conducted to test the effect of Ascophyllum nodosum extract on the growth of Robinia pseudoacasia L., ornamental tree. In vitro and ex vitro clonal multiplication of Robinia pseudoacasia L. was achieved using embryonic axes and seeds as explants, respectively. Factors affecting shoot and root production of R. pseudoacasia L. were investigated by comparing various growth regulators [α-naphthalene acetic acid (NAA) and 6-benzylaminopurine (BA)] and culture media [Murashige and Skoog (MS) and WPM (woody plant medium)] on in vitro conditions, also culture beds (sand, perlite, compost and cocopeat) with different ratios and extracts of brown seaweed Ascophyllum nodosum on ex vitro conditions. Both of BA and NAA were used at concentrations of 0, 0.5, 1 and 1.5 mg l-1. Concentrations used from extracts of A. nodosum were 0, 1000, 2000 and 3000 mg l-1. The optimum plant growth regulator (PGR) combination for maximal plant height, shoot number, node number, root number, root length, leaf number, fresh and dry weight on in vitro condition was 1 mg l-1 NAA and 1 mg l-1 BA in MS medium. The 1000 mg l-1 of extracts of A. nodosum led to optimum plant height, node number, longest root, leaf number, dry weight, fresh weight.  The most appropriate plantlets survival on ex vitro condition was observed when the culture medium was a bed containing sand + perlite + compost with proportion of 1:1:1. About 75% of the propagated plantlets and 90% of the micropropagated plantlets were established successfully in acclimatization medium. Regenerated plantlets were morphologically identical with mother plants. Present study showed positive modifications in shoot proliferation, rate of rooting of stem and some morphological and physiological characters due to subjection of R. pseudoacasia L. to optimum treatments.