The Impact of Auxin and Cytokinin on the Growth and Development of Selected Crops

Abstract

With a very diverse structure and small molecules, phytohormones are regulators of plant growth and development. Despite the fact that they are synthesized by plants in small quantities, they are highly active physiologically. According to their action, phytohormones can be divided into two categories, as either activators of plant growth and development or as inhibitors, with auxins and cytokinins belonging to the former group. Auxins are synthesized by plants in the apical meristems of shoots, but also in young leaves, seeds, and fruits. They stimulate the elongation growth of shoots and initiate the production of adventitious and lateral roots. Cytokinins, in turn, are formed in root tips and in unripe fruits and seeds. These hormones are responsible for stimulating the growth of lateral shoots, they also stimulate cytokinesis and, consequently, cell division. The aim of this review paper is to present the progress of the research on the effect of selected auxins and cytokinins on crops, considering the prospect of using them in plant growing methods.

In Vitro Propagation of Philodendron erubescens ‘Pink Princess’ and Ex Vitro Acclimatization of the Plantlets

“…[7], compared with other cytokinins. Furthermore, a recent study also reported that combining cytokinins and auxins stimulated the elongation of shoots and yielded a more significant shoot number, shoot length, and fresh weight of several crops, including Philodendron bipinnatifidum, than treatments with cytokinins alone [16,22]. Thus, the effect of cytokinin (BAP) and auxin (NAA) at different concentrations on the shoot prolifera-tion of Philodendron erubescens pink princess was investigated in this study.…”

“…Generally, NAA, a member of the auxin family, plays an essential role in plant cell growth, differentiation, and development, specifically the formation of roots [24,25]. Although auxins have been reported to stimulate shoot elongation [22], the application of NAA alone did not significantly improve the shoot formation of Philodendron pink princess compared to the control without the supplementation of PGRs (Treatment 1). Considering the combinations of BAP and NAA, these treatments did not exert a synergistic effect on shoot proliferation compared with treatment using BAP at 1.0 mg/L alone.…”

“…Notably, the combination of BAP at 2 mg/L and NAA at 1.0 mg/L (Treatment 9) yielded the lowest number of shoots (2.7 shoots/explant) and leaves (2.3 leaves/explant) compared to the control and other treatments. This observation could be attributed to a hormonal imbalance, which may alter the action of another hormone, leading to the suppression of shoot and leaf formation and growth [22,26].…”

“…Auxins are among the most critical PGRs since they are involved in all physiological processes in plants. They promote shoot elongation and initiate the formation of adventitious and lateral roots [22]. Different plant species have diverse responses to different kinds and concentrations of auxins.…”

Effect of Exogenous Tryptophan on Primary Metabolism and Oxidative Stress and Their Relationship with Seedling Germination and Vigor of Glycine Max L.

“…This is because tryptophan, even if exogenously supplied, increases the tissue levels of auxin in soybeans. Auxins belong to the class of hormones activating plant growth and development [49], directly affecting cell division, elongation, and differentiation [50]. There is clear evidence that these hormones induce H + ion excretion and consequent tissue elongation of soybean hypocotyls [51].…”