Leaf anatomy micromorphometry plasticity and histochemistry of Azadirachta indica during acclimatization

Marcelo Rodrigues,Reginaldo Alves Festucci-Buselli,Ane Marcela Das Chagas Mendonça,Diego Ismael Rocha,Wagner Campos Otoni,Luzimar Campos Da Silva

doi:10.1590/2175-7860202071019

Abstract

Abstract Environmental conditions of grow can modify leaf structure and metabolite production. Neem plants produce a high amount of medicinal metabolites and contain biopesticide terpenoids with low toxicity. However, the high genetic variation and the low material quality, besides the environmental modifications warn to the need of biotechnological techniques to ensure the production of high quality metabolites. The aim was to investigate leaf structural and histochemical characteristics of Azadirachta indica grown in vitro, in vivo and acclimatized condition. It was found anatomical differences among the environments, with higher leaf thickness associated to in vivo conditions, as well as were more evenly distributed stomata. Those modifications did not qualitatively affect the production of medicinal metabolites and biopesticides. Terpenes and tannins were observed in specialized cells called idioblasts, located in the mesophyll and in the midrib region, respectively. Thus, in a qualitative approach, we can affirm that the different environments do not modify metabolites production. Increased production of these bioactive compounds could be achieved by isolation and in vitro culture of idioblasts as a new source of research in plant biotechnology.

Highlights

After the transfer of plants from cultures in vitro to the greenhouse or field, substantial changes in leaf morphology and anatomy are observed, including characteristics of the epidermis, the thickness of cuticle and leaves, the differentiation of mesophyll, the number and structure of stomata and chloroplasts (Pospíšilová et al 1999; Sáez et al 2012; Mani & Shekhawat 2017), the structure and amount of epicuticular wax on the top surface of the leaves, the number of trichomes and the intercellular spaces of the mesophyll (Fanourakis et al 2013; Shekhawat & Manokari 2018)
It is important to use anatomical analyses to characterize structural changes in plants caused by environmental conditions and in the survival rate of transplanted plantlets related to abnormal morphogenesis, stomatal malfunction (Apóstolo et al 2005; Shekhawat & Manokari 2018) and variations in the production of bioactive compounds (Murthy et al 2014)
The aim of this study was to examine the structural differences in the leaves of A. indica grown in vivo and in vitro conditions, as well as acclimatized plants; this work investigates the presence of terpenoids, tannins, lipids, mucilage and their respective cell types in the accumulation of these medicinal metabolites and biopesticides in leaves of Neem developed in these three environments

Summary

Introduction

After the transfer of plants from cultures in vitro to the greenhouse or field, substantial changes in leaf morphology and anatomy are observed, including characteristics of the epidermis, the thickness of cuticle and leaves, the differentiation of mesophyll, the number and structure of stomata and chloroplasts (Pospíšilová et al 1999; Sáez et al 2012; Mani & Shekhawat 2017), the structure and amount of epicuticular wax on the top surface of the leaves, the number of trichomes and the intercellular spaces of the mesophyll (Fanourakis et al 2013; Shekhawat & Manokari 2018). Different environmental factors and conditions, such as atmospheric carbon concentration, temperature, relative humidity and photosynthetic active radiation during acclimatization of some species, may modify anatomical features, in the same way that changes medicinal metabolites and biopesticide production in this species (Sidhu et al 2003; Arora et al 2016). In this context, it is important to use anatomical analyses to characterize structural changes in plants caused by environmental conditions and in the survival rate of transplanted plantlets related to abnormal morphogenesis, stomatal malfunction (Apóstolo et al 2005; Shekhawat & Manokari 2018) and variations in the production of bioactive compounds (Murthy et al 2014). The remarkable bioinsecticide terpenoids against a wide range of agricultural pests and the advantage of being environmentally harmless have increased interest in this class of compounds (Campos et al 2016)

Objectives

Methods

Results

Discussion

Conclusion