Leaf Response to Different Light Spectrum Compositions during Micropropagation of Gerbera Axillary Shoots

Bożena Pawłowska,Monika Cioć

doi:10.3390/agronomy10111832

Abstract

The experiment evaluated the influence of different light qualities and 6-benzyladenine (BA) concentration in a medium on the leaf response of multiplied Gerbera jamesonii Bolus ex Hook. f.‘Big Apple’ shoots. Three different light-emitting diode (LED) spectra—100% blue (B), 100% red (R) and red and blue mixture (7:3, RB)—were used, and a fluorescent lamp was used as a control (Fl). Concentrations of BA in Murashige and Skoog (MS) medium were 1, 2.5 and 5 µM. Leaves developed under 100% blue light had a lower frequency of stomata and a smaller area as compared with those from plants exposed to light with red in spectrum. Under 100% red light, the leaf area and the frequency of stomata increased along with growing concentration of BA in the medium. The thickest mesophyll was spotted in the cross-section of leaves exposed to the blue LED light. Leaves developed under the 100% red light had the thinnest mesophyll layers. Increasing concentration of BA in the medium resulted in enhanced leaf blade thickness. The cross-section of leaf vascular bundles was only half of that in petioles. The leaves under the LED combinations had larger vascular bundles than those under fluorescent light. The highest level of photosynthetic pigments was noticed in the leaves grown under LED R and RB lights. Our study demonstrated that 2.5 µM BA and a mixture of blue and red light provided by LED improved leaf quality during multiplication of gerbera shoots.

Highlights

Plants cultivated in vitro have limited photosynthetic abilities, which is why light exerts the greatest effect on morphogenesis under these conditions
A 20x magnification was used to measure the thickness of the entire cross-section, of the upper and lower epidermis and of the spongy and palisade mesophyll and the width and length of the vascular bundles of the leaf blade (Figure 1c–d)
Different light qualities applied during in vitro shoot multiplication of gerbera changed the thickness of leaf blades and petioles and the level of photosynthetic pigments

Summary

Introduction

Plants cultivated in vitro have limited photosynthetic abilities, which is why light exerts the greatest effect on morphogenesis under these conditions. External factors of a culture, mainly the spectral quality of light and growth regulators in the medium, affect plant growth and development in vitro. Plant response manifests itself in external morphological changes at every stage of clonal propagation and at the anatomical level. Leaves show high phenotypic plasticity as a response to light conditions and the modifications are easier to observe than those in stems or roots [1]. The epidermis and other tissue layers are often less developed and thinner than in traditionally cultivated plants, as the humidity inside the vessels is relatively high. Evaluation of structural changes in a tissue or organ formed in vitro is of great value in establishing the actual efficiency of organogenesis and the functioning of new organs, such as leaves [3]

Methods

Results

Conclusion