Physiological Mechanism Involved in the Response to Four Lettuce Varieties to a Pre-transplant Root Restriction and a 6, benzyl aminopurine (BAP) Spray

Abstract

Vegetable yield is positively related to the environment and negatively affected by the pot root restriction during both the nursery and post-transplant stages. Root restriction is a physical stress imposed on the root system when plants are grown in small containers, which leads to a pronounced decrease in root and shoot growth at both the transplant and pot stages. Based on the assumption that the plant responses are mainly associated with a negative hormonal signaling from roots, some researchers have proposed that these abiotic stresses may be overridden by using a pre-transplant spray with benzyl amino purine (BAP), a synthetic cytokinin able to regulate plant metabolism. Although the physiological mechanisms induced by BAP have been described, the implementation of commercial applications of BAP for vegetables is still a pending issue. The aim of this work was to analyze growth changes in four lettuce genotypes in the presence of different root restrictions degree by the use of different plug cell volumes but sprayed with a single BAP spray under the hypothesis that it would play a role as abiotic stress alleviators. Our results showed that the higher biomass accumulation in lettuce plants non root-limited and BAP-sprayed ones are supported by higher photosynthetic rates, by higher leaf number initiation and expansion and by photo assimilate partition to shoots. Understanding the plant responses to this hormonal manipulation and the physiological mechanism involved will allow adjusting the agronomic advice for different vegetables and reaching commercial yields to each of them.

Effect of Benzyl Amino Purine (BAP) on the Leaf Growth of Vanda limbata Blume Orchid In Vivo

“…In addition, in sustainable agriculture, it is necessary to use environmentally friendly materials, hence the choice of BAP-type cytokinins because their content is similar to the natural plant hormones that are friendly to the environment. According to Campolongo et al (2020), BAP is considered a compound that is very similar to endogenous cytokinins because it presents a very low risk to the environment, as it is non-toxic to mammalian and arthropod species. Based on this, BAP is suitable for supporting sustainable agriculture.…”

“…Cytokinin in the roots only synthesizes cytokinin; then cytokinin will be transported to the nodes for branching and leaves. This is supported byCampolongo et al (2020) that cytokinins are mainly synthesized in the roots, then move through the stem xylem to the shoot apical meristem and increase cell division to form new shoots. The results of this research are similar to the results of the study byHadiati (2011) on the immersion of BAP concentrations of 200 to 600 mg l -1 in pineapple (Ananas comosus L.) stem cuttings, in which the immersion of BAP did not have a significant effect on the number of pineapple roots at 17 weeks of age.…”

Root-shoot growth and time to transplant of different lettuce genotypes during nursery

“…This choice allows increasing plant density, but has the disadvantage that it restricts root growth, followed by considerable changes in plant growth and physiology (1). In addition, although seedling trays with individual small cell sizes allow short plant-raising periods and reduced costs, larger plugs produce a finished pot plant after transplant in a shorter period of time than smaller plugs (3).…”