In vitro and in vivo bio-stimulatory properties of a Lupinus albus L. seed suspension

Abstract

During an extended screening program of plant extracts for bio-stimulatory activity, a seed suspension (SS) of Lupinus albus L. cv. Betsuhana White was identified as most promising. By testing a concentration range of SS using three in vitro bio-assays [i.e. respiration rate of monoculture yeast (Saccharomyces cerevisiae) cells, germination rate of seeds from selected crops, and subsequent seedling growth], 5 mg/L was identified as the optimal concentration in terms of in vitro bio-stimulatory activity. A commercially available bio-stimulant, ComCat®, was used as a positive control, while a glucose solution for respiration tests and distilled water for germination tests served as negative controls. Compared with the controls, significant (P < 0.05) increases in the respiration rate of monoculture yeast cells and seedling root growth in the majority of test crops after treatment with SS confirmed its in vitro bio-stimulatory potential. Seedling root growth compared favourably with results obtained with the commercial bio-stimulant. Subsequently, the in vivo yield response of selected crops to foliar treatment with SS was investigated under field conditions using ComCat® as a positive control. All trials were laid out in a complete randomised block design. Foliar applications of SS at 5 mg/L under a drip irrigation system contributed to significant (P < 0.05) yield increases in lettuce (by 20.0 t/ha) and carrots (by 22.2 t/ha), which compared favourably with the positive control, but not in beetroot and cabbage. Beetroot yield was enhanced whereas cabbage yield was decreased markedly, but not significantly, by the SS treatment, compared with the negative control. The results confirmed both the in vitro and in vivo bio-stimulatory potential of a seed suspension of L. albus cv. Betsuhana White in terms of its ability to manipulate early seedling growth and enhance the yield of selected vegetable crops.