Overcoming Physiological Bottlenecks of Leaf Vitality and Root Development in Cuttings: A Systemic Perspective

Uwe Druege

doi:10.3389/fpls.2020.00907

Abstract

Each year, billions of ornamental young plants are produced worldwide from cuttings that are harvested from stock plants and planted to form adventitious roots. Depending on the plant genotype, the maturation of the cutting, and the particular environment, which is complex and often involves intermediate storage of cuttings under dark conditions and shipping between different climate regions, induced senescence or abscission of leaves and insufficient root development can impair the success of propagation and the quality of generated young plants. Recent findings on the molecular and physiological control of leaf vitality and adventitious root formation are integrated into a systemic perspective on improved physiologically-based control of cutting propagation. The homeostasis and signal transduction of the wound responsive plant hormones ethylene and jasmonic acid, of auxin, cytokinins and strigolactones, and the carbon-nitrogen source-sink balance in cuttings are considered as important processes that are both, highly responsive to environmental inputs and decisive for the development of cuttings. Important modules and bottlenecks of cutting function are identified. Critical environmental inputs at stock plant and cutting level are highlighted and physiological outputs that can be used as quality attributes to monitor the functional capacity of cuttings and as response parameters to optimize the cutting environment are discussed. Facing the great genetic diversity of ornamental crops, a physiologically targeted approach is proposed to define bottleneck-specific plant groups. Components from the field of machine learning may help to mathematically describe the complex environmental response of specific plant species.

Highlights

Plant propagation is the initial process of producing ornamental crops that already sets the first benchmark for the whole cultivation process by determining the quality of the young plant
Leaf retention and greenness and adventitious root formation in the stem base are the two targets of cutting function that determine the final quality of the young plant, while physiological outputs can be used to monitor the cutting performance
indole-3-acetic acid (IAA) accumulation in the stem base is dependent on auxin re-mobilization from the upper shoot, with developing leaves (DL) and fully developed leaves (FL) as potential auxin sources and polar auxin transport (PAT) as important process of translocation

Summary

Introduction

Plant propagation is the initial process of producing ornamental crops that already sets the first benchmark for the whole cultivation process by determining the quality of the young plant. Depending on the plant genotype and configuration of environmental inputs at stock plant and cutting level, different processes may constitute the bottleneck (B) of cutting function (Figure 1).

Results

Conclusion