Plant Production and Leaf Anatomy of Mertensia maritima (L.) Gray: Comparison of In Vitro Culture Methods to Improve Acclimatization

Barbara Ruffoni,Laura Cornara,Miriam Bazzicalupo,Arianna Cassetti,Andrea Copetta,Carlo Mascarello,Laura Pistelli,Ilaria Marchioni

doi:10.3390/horticulturae7050111

Barbara Ruffoni, Laura Cornara + Show 6 more

Open Access

https://doi.org/10.3390/horticulturae7050111

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Abstract

Mertensia maritima is a commercially interesting herb with edible leaves and flowers, characterized by oyster flavor and taste. Plant propagation and traditional cultivation are challenging for this species. Therefore, the main purpose of the present study was to establish successful protocols aimed at ensuring oyster plant shoot propagation, rooting and in vivo acclimatization. Both micropropagation and rooting were tested, comparing the traditional in vitro solid substrate in jar vs. the liquid culture in a temporary immersion system (TIS) bioreactor (Plantform™). A Murashige and Skoog (MS) medium added with 4-μM thidiazuron (TDZ) and 1-μM α-naphthaleneacetic acid (NAA) was employed for micropropagation, while a half-strength MS medium supplemented with 4-μM indole−3-butyric acid (IBA) was used for rooting. Different acclimatization conditions in the greenhouse or in growth chamber were tested. Morphometric and microscopical analyses were performed on the oyster plant leaves at the propagation, rooting and acclimatization stages both in a jar and in a TIS. Micropropagation in a TIS allowed to obtain large shoots, while a great number of shoots was observed in the jar. M. maritima shoots rooted in TIS produced more developed roots, leaves with more developed waxy glands and well-formed stomata; moreover, the plants coming from the TIS showed the best acclimatization performances.

Highlights

Mertensia maritima (L.) Gray (Boraginaceae family) is a perennial herb, which has a circumboreal distribution, and it is found in sea coastal habitats like shingle beaches, growing around the high-tide mark and, rarely, on sand [1]
The shoots micropropagated in the temporary immersion system (TIS) appeared larger than the micropropagated shoots with the classic jar system with a solid substrate (Figure 2)
For these last two reasons, and because the explants produced in the jar had more homogeneous dimensions, the micropropagation in the jar system was chosen to produce M. maritima shoots to be used for the subsequent experiments of rooting induction

Summary

Introduction

Mertensia maritima (L.) Gray (Boraginaceae family) is a perennial herb, which has a circumboreal distribution, and it is found in sea coastal habitats like shingle beaches, growing around the high-tide mark and, rarely, on sand [1]. The plant is an upright rosette consisting of glaucous blue-green leaves with wax glands on the upper surface and can reach 20 cm in height. The flowers are 4–6 mm long with an initial pink color that gradually changes to blue or pink/blue hues because of the flower’s development process [1]. The interest in this herb is due to the surprising marine oyster-like aroma and taste of its edible leaves and flowers, as reported by Delort and collaborators [2], who analyzed, in 2012, the volatile composition of M. maritima leaves. M. maritima is called a vegetarian oyster or oyster plant, and their leaves are used to prepare

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