Increase of Spinach Growth Through the use of Larger Plug Cell Volume and an Exogenous BAP Spray

Abstract

Aims: In spinach, transplanting has replaced direct seeding but small containers may cause root restriction effects that would be decreased post-transplant yield. Although a single hormonal regulator (BAP) spray is effective in overcoming root restriction, the mechanisms involved are unknown. The aim of this work was to analyze spinach growth changes by the use of different plug cell volumes and BAP as foliar spray. Study Design: A randomized complete block factorial design with three blocks was used. Place and Duration of Study: The experiments were conducted at the INTA Balcarce Experimental Station campus, Argentina (37º 45′ S, 58° 18′ W and altitude 130 m) from 5th March to 24th May 2008 and repeated once from 15th March to 19th May 2009. Methodology: We analyzed growth changes by the use of different plug cell volumes and BAP as foliar spray on dry weight accumulation and partitioning in Spinacea oleracea plants in two field experiments. Results: The use of large plug cell volumes and BAP sprays at the pre-transplant stage increased plant growth, through an increase in the relative growth rate (RGR) and the rate of leaf area expansion (RLAE). We found a close direct relationship between RGR and net assimilation rate (NAR) but an inverse relationship between RGR and leaf area ratio (LAR). In addition, we found that NAR significantly increased as leaf thickness, intercellular spaces and stomatal density increased. A change in dry weight partitioning toward shoots was found as well. Conclusion: From a grower’s point of view, the use of large plug cell volume would increase spinach growth. On the other hand, a promising approach to increasing crop productivity is the use of plant growth and development regulators such as BAP.