Nair S. Yokoya1, Wendy A. Stirk2, Johannes van Staden2
1Biodiversity Conservation Center, Environmental Research Institute, Av. Miguel Estéfano 3687, Água Funda, São Paulo, SP, 04301-902, Brazil
2Research Centre for Plant Growth and Development, School of Life Sciences, University of KwaZulu-Natal Pietermaritzburg, P/Bag X01, Scottsville 3209, South Africa
The cytokinin-like (CK) activities were analysed in eight species of Rhodophyta: Chondracanthus teedii, Dichotomaria marginata, Gelidium floridanum, Gracilaria birdiae (tetrasporophytes and female gametophytes), Gracilaria cervicornis, Gracilaria domingensis (field and cultured samples), Gracilaria tenuistipitata, and Hypnea pseudomusciformis (color and morphological variants). Samples were extracted for 24 h at 10ºC in 100 ml 80% ethanol, filtered, rinsed with 80% ethanol, and purified using C18 Sep-Pak cartridges. CK activities were determined using the soybean callus bioassay with activity compared with kinetin standards at concentrations from 1 to 50 µg L-1. C. teedii had activities equivalent to 5-10 µg L-1, that co-chromatographed with isopentenyladenine (iP), and riboside-5’-monophosphate (MP), while Gelidium floridanum had activities equivalent to 1-5 µg L-1. D. marginata and G. tenuistipitata showed low CK-activities. Tetrasporophytes and female gametophytes of G. birdiae had activities which co-chromatographed with zeatin (Z) with female gametophytes having an extra peak that co-chromatographed with MP. The highest activity (equivalent to 50 µg L-1) was observed in G. cervicornis, while G. domingensis grown in culture had no activity, but field samples had activity which co-chromatographed with the MP and O-glucosides (OG). The Hypnea green strain showed more activity (equivalent to 5 µg L-1) than the brown strain (equivalent to 1 µg L-1) with most activity co-chromatographing with Z. Morphological variants of Hypnea had similar activities, but “nigrescens” variant had peaks that co-chromatographed with zeatin riboside (ZR) and isopentenyladenosine (iPR). The results indicate that some red algae studied have potential as biostimulant in agriculture. Financial supports: CNPq, FAPESP.