Seasonal Changes in the Levels of Endogenous Cytokinins in Sargassum heterophyllum (Phaeophyceae)

Abstract

A seasonal analysis of cytokinin activity in Sargassum heterophyllum (Turn.) J. Ag. was undertaken. The data thus obtained show that there are pronounced quantitative and qualitative seasonal changes in the cytokinin content of the holdfast, vegetative and reproductive laterals. These changes correspond with the seasonal periodicity of growth, development and reproduction of this alga. Three major peaks of activity were detected: a polar peak, which co-chromatographed with glucosylzeatin, and two non-polar peaks which had the same Chromatographie properties äs zeatin and ribosylzeatin, and äs isopentenyladenosine and isopentenyladenine, respectively.

Endogenous cytokinins, auxins and abscisic acid inUlva fasciata(Chlorophyta) andDictyota humifusa(Phaeophyta): towards understanding their biosynthesis and homoeostasis

“…It may be expected that if plant hormones are important in regulating growth and developmental processes in seaweeds, they will show some seasonal fluctuations in their composition and concentrations. Studies in the 1980s demonstrated there was a seasonal variation in cytokinin-like activity in some brown seaweeds, with an increase in cytokinin-like activity (cytokinin free bases and riboside-like activity) in samples collected during periods of active growth, while there was an increase in cytokinin-O-glucoside-like activity in samples collected during periods of slower growth in Ecklonia maxima (Featonby-Smith & van Staden, 1984), Sargassum heterophyllum (Mooney & van Staden, 1984) and Macrocystis pyrifera (de Nys et al, 1990). Cytokinin-like activity also increased in the vegetative laterals of Sargassum heterophyllum to coincide with gamete release and the onset of regenerative growth, while activity in the reproductive laterals increased to coincide with gamete release and receptacle initiation (Mooney & van Staden, 1984).…”

“…Studies in the 1980s demonstrated there was a seasonal variation in cytokinin-like activity in some brown seaweeds, with an increase in cytokinin-like activity (cytokinin free bases and riboside-like activity) in samples collected during periods of active growth, while there was an increase in cytokinin-O-glucoside-like activity in samples collected during periods of slower growth in Ecklonia maxima (Featonby-Smith & van Staden, 1984), Sargassum heterophyllum (Mooney & van Staden, 1984) and Macrocystis pyrifera (de Nys et al, 1990). Cytokinin-like activity also increased in the vegetative laterals of Sargassum heterophyllum to coincide with gamete release and the onset of regenerative growth, while activity in the reproductive laterals increased to coincide with gamete release and receptacle initiation (Mooney & van Staden, 1984). The highest cytokinin-activity (free base and riboside-like activity) was detected near the intercalary meristem in the youngest blades of Macrocystis pyrifera, whereas the older portions of the blade had higher levels of cytokinin-O-glucoside-like activity (de Nys et al, 1990).…”

Acclimation of brown seaweeds in an outdoor cultivation system and their cytokinin-like activity

“…Its breakdown at the end of August was a natural disintegration presumably related to its annual life form. In its natural bed, it is almost absent from September to November, while during the rest of the year it covers several (Borowczak et al, 1977), Sargassum heterophyllum (Mooney and Van Staden, 1984a) and Ecklonia maxima (FeatonbySmith and Van Staden, 1984). The total species 'final extract' showed enhancement activity in two other assays: germination and growth of bean and lettuce seedlings.…”

“…The radish, soybean and lettuce assays contributed a new aspect to the existing cytokinin promoting activities in bananas, potatoes, maize, peppers, tomatoes, pineapples, peaches and oranges (Chapman and Chapman, 1980). Three cytokinin isolation steps were performed in order to compare the activity of the crude extract of Dictyopteris membranacea with previous information (Mooney and Van Staden, 1984a) and to characterize its cytokinin-like activity. The first step (ashing) showed that the aging inhibition is affected by both the ash and organic fractions of the 'final extract'.…”

“…The following cytokinin fractionation is according to Van Staden (1976) and Mooney and Van Staden (1984a). Ten grams of fresh Dictyopteris were blended in 100 ml of 80% ethanol and kept for 24 h at 5 C. Ten grams of polyvinyl pyrolidon were added to the suspension for an additional 24 hours at 5 C. The extract was filtered through Whatman-1 filter paper, washed with 50 ml of 800% ethanol, and evaporated at 35 °C until its aqueous residue was left (sample 1).…”