Heino B. Papenfus

Seasonal variation in the polyamines of Ecklonia maxima

Abstract The seaweed concentrate (SWC) Kelpak® is made from Ecklonia maxima (Osbeck) Papenfuss and is used as a biostimulant in agriculture. Cytokinins and auxins have been identified in Kelpak® and are partly responsible for the growth-promoting effects observed. Other biologically active compounds such as polyamines (PAs) might also be present in the SWC. A study was carried out to investigate the PA levels in E. maxima and Kelpak®. The stipes, fronds, and SWC prepared from E. maxima were collected monthly over a 2-year period. Extracts were benzoylated, and endogenous PAs were quantified using high-performance liquid chromatography. Putrescine concentrations ranged from 6.10 to 40.40 μg g-1 dry weight (dw), from 15.98 to 54.46 μg g-1 dw, and from 0.98 to 5.51 μg ml-1 in the stipe, fronds, and SWC, respectively. Spermine concentrations ranged from 1.02 to 35.44 μg g-1 dw, from 1.05 to 27.35 μg g-1 dw, and from 1.27 to 4.95 μg ml-1 in the stipe, fronds, and SWC, respectively. Spermidine concentrations fell below the detection threshold. This is the first report of PAs being detected in a SWC. The seasonal pattern established for the stipe, frond, and SWC followed the same trend over a biennial cycle, with PAs accumulating in the seaweed tissue during periods of active growth and during periods of rough wave action (stress response).

Effect of smoke derivatives on in vitro pollen germination and pollen tube elongation of species from different plant families

Plant-derived smoke stimulates seed germination in numerous plant species. Smoke also has a positive stimulatory effect on pollen germination and pollen tube growth. The range of plant families affected my smoke still needs to be established since the initial study was restricted to only three species from the Amaryllidaceae. The effects of smoke-water (SW) and the smoke-derived compounds, karrikinolide (KAR1 ) and trimethylbutenolide (TMB) on pollen growth characteristics were evaluated in seven different plant families. Smoke-water (1:1000 and 1:2000 v:v) combined with either Brewbaker and Kwacks (BWK) medium or sucrose and boric acid (SB) medium significantly improved pollen germination and pollen tube growth in Aloe maculata All., Kniphofia uvaria Oken, Lachenalia aloides (L.f.) Engl. var. aloides and Tulbaghia simmleri P. Beauv. Karrikinolide (10(-6) and 10(-7) m) treatment significantly improved pollen tube growth in A. maculata, K. uvaria, L. aloides and Nematanthus crassifolius (Schott) Wiehle compared to the controls. BWK or SB medium containing TMB (10(-3) m) produced significantly longer pollen tubes in A. maculata, K. uvaria and N. crassifolius. These results indicate that plant-derived smoke and the smoke-isolated compounds may stimulate pollen growth in a wide range of plant species.

PLANT GROWTH REGULATORS ENHANCE GOLD UPTAKE IN BRASSICA JUNCEA

The use of plant growth regulators is well established and they are used in many fields of plant science for enhancing growth. Brassica juncea plants were treated with 2.5, 5.0 and 7.5 μM auxin indole-3-butyric acid (IBA), which promotes rooting. The IBA-treated plants were also sprayed with 100 μM gibberellic acid (GA3) and kinetin (Kin) to increase leaf-foliage. Gold (I) chloride (AuCl) was added to the growth medium of plants to achieve required gold concentration. The solubilizing agent ammonium thiocyanate (1 g kg−1) (commonly used in mining industries to solubilize gold) was added to the nutrient solution after six weeks of growth and, two weeks later, plants were harvested. Plant growth regulators improved shoot and root dry biomass of B. juncea plants. Inductively Coupled Plasma Optical Emission Spectrometry analysis showed the highest Au uptake for plants treated with 5.0 μM IBA. The average recovery of Au with this treatment was significantly greater than the control treatment by 45.8 mg kg−1 (155.7%). The other IBA concentrations (2.5 and 7.5 μM) also showed a significant increase in Au uptake compared to the control plants by 14.7 mg kg−1 (50%) and 42.5 mg kg−1 (144.5%) respectively. A similar trend of Au accumulation was recorded in the roots of B. juncea plants. This study conducted in solution culture suggests that plant growth regulators can play a significant role in improving phytoextraction of Au.

Smoke-Isolated Trimethylbutenolide Inhibits Seed Germination of Different Weed Species by Reducing Amylase Activity

Abstract Weeds pose a great problem to farmers worldwide, and controlling weeds demands a high input cost for herbicides and labor. Because of current environmental regulations, a limited number of herbicides are commercially available (with limited modes of action) to control weeds. Smoke water and the biologically active compounds isolated from smoke affect seed germination in a significant way. Smoke water (SW) and karrikinolide (KAR1, the germination stimulant isolated from smoke) have been tested extensively for their ability to promote seed germination in a vast array of plant species. In addition to KAR1, a germination inhibitor, trimethylbutenolide (TMB), was also isolated from plant-derived smoke. The effects of SW, KAR1, and TMB were tested on five major weed species of South Africa: fleabane, hairy wild lettuce, bugweed, spilanthes, and fameflower. Seeds of these weed species were subjected to 16/8 h light/dark conditions or to constant dark conditions at constant temperatures of 20, 25, 30 C and alternating 30/20 C. SW and KAR1 significantly increased germination, whereas TMB significantly inhibited germination of these weed species. Furthermore, TMB treatment reduced the amylase activity of the tested weed seeds compared with the water control. These results indicate the possibility of manipulating germination of certain weed seeds by SW, KAR1, and TMB. Thus, smoke and smoke-isolated compounds could potentially be used in new weed management strategies. Nomenclature: Karrikinolide, KAR1, 3-methyl-2H-furo[2,3c]pyran-2-one; trimethylbutenolide, TMB, 3,4,5-trimethylfuran-2(5H)-one; bugweed, Solanum mauritianum Scop.; fameflower, Talinum paniculatum (Jacq.) Gaertn.; fleabane, Conyza albida Willd. ex Sprengel; hairy cats ear, Hypochaeris radicata L.; spilanthes, Spilanthes decumbens (Sm.) A.H. Moore.