Effects of spindle inhibitors and phytoregulators on the micropropagation of Kappaphycus alvarezii (Rhodophyta, Gigartinales)

Spindle inhibitors and phytoregulators are substances largely used to improve the growth of plants with commercial interest. This study analyzes the effects of colchicine (Ch) and oryzalin (Oz), two spindle inhibitors, on the survival and growth rates of Kappaphycus alvarezii micropropagules when combined in cultures with such phytoregulators as indole-3-acetic acid (IAA), kinetin (K), and spermine (S), aiming to improve mass cultivation under laboratory conditions. Explants were first cultured in treatments of colchicine and oryzalin, separately or in combination, for 2 weeks. Afterwards, they were cultured in sterilized seawater enriched with 50 % von Stosch solution. All explants produced upright axes from the cut or lateral region. Treatment with 1.0 mg L-1 oryzalin significantly increased the formation of upright axes (4.89 +/- 1.60 upright axes explant(-1)) compared to control (1.33 +/- 0.16 upright axes explant(-1)). Explants treated with oryzalin alone or in combination with IAA or kinetin showed a significantly higher production of upright axes, while those treated with oryzalin in combination with spermine or other phytoregulators (IAA and K; IAA and S; K and S; IAA, K, and S) showed a significant increase of growth rates, ranging 3.47 +/- 0.27 % day(-1)in control to 4.98 +/- 0.47 % day(-1)in the IAA:S + Oz treatment. Results showed that oryzalin in combination with phytoregulators, such as IAA, spermine, or kinetin, affects micropropagule production and growth, thereby improving the mass cultivation of K. alvarezii but without affecting the survival rates of explants.