Exogenous BAP Spray Applications against to Abiotic Stress Related by Root Restrictions in Spinach

Previous reports showed that the abiotic stress related to the pre-transplant plug cell volume during nursery decreases both root and shoot growth at the transplant stage and limit final yield to leafy green vegetables. The cytokinin function has been linked to different abiotic stresses including plug cell volume during nursery, which explain that a single early benzyl amino purine (BAP) spray can override root restriction effects. Since transplanting has almost replaced direct seeding, the objective of this new report was to analyze spinach growth changes of different root restrictions degree by direct-seeded or the use of different plug cell volumes but including the use of the hormonal regulator BAP as an abiotic stress alleviator at different times. Our results showed that higher yield has been related to leaf area expansion (estimated through RLA, RLAE and individual leaf size), photo assimilate acquisition (estimated through RGR, NAR and SLA), and photo assimilate partition (estimate through root-shoot allometries). All traits can be modified by root restriction during nursery and a single BAP spray. On the other hand, a direct relationship between RLAE, RLA, RGR, NAR, glucose content and root dry weight was found. However, the precise quantitative response is related to BAP application time as well. In summary, plug cell volume can be considered as an abiotic stress, which decreases spinach yield. Shoot-biomass accumulation can be optimized through direct-seeded, increased plug cell volume or applied a single BAP spray in plug-grown plants. However, a precise BAP application time and spinach response relationship can be shown.