Seedling emergence and growth of ‘China Rose’ radish microgreens in response to radicle breakage following pre-sowing seed germination

Abstract

ABSTRACT Germinating seeds in moist, fine-grade vermiculite followed by broadcasting the mix over the seedbed can reduce greenhouse production time for microgreens, but seedling radicles could be broken. The study was undertaken to determine if radicle breakage affected plant yield of radish (Raphanus sativus L) used for microgreens. During pre-sowing handling of germinated seed in moist vermiculite the percent of broken radicles increased as radicle length increased, and as mechanical force increased (resulting in 0%, 8%, or 22% with minimal, medium or high mechanical force, respectively). Imposition of these levels of radicle damage was achieved by cutting radicles half-way along their length after germination for 2 days in moist vermiculite (200% water, dry weight) at which time radicles were about 1.5 cm long. This treatment had no effect on numbers of shoots (as a percent of sown seed) or number of shoots∙m−2 at 7 days after sowing at 25% or 100% of a commercial rate (9,266 seed∙m−2). Yield as shoot fresh weight∙m−2, or per seedling was unaffected by percent of cut radicles sown. Removal of up to 12 mm of radicle from the tip increased numbers of roots per seedling but decreased total root length and decreased fresh weight per shoot. The higher seeding rate decreased fresh weight per shoot from raw (42%) or germinated (32%) seed. Sowing germinated seed in moist vermiculite, rather than raw seed, and sowing seed at the higher rate, increased shoot fresh weight∙m−2 and shoot fresh weight per seedling. Seedlings with broken radicles had lower shoot fresh weights but smaller shoots were counted in the final yield. Microgreen yield (shoot fresh weight∙m−2) was unaffected after sowing germinated seed that had been subjected to a high mechanical force (with up to 22% broken radicles) during broadcasting .