Effects of NAA and Ecklonia maxima Extracts on Lettuce and Tomato Transplant Production

Alessandra Moncada,Alessandro Esposito,Alessandro Miceli,Filippo Vetrano

doi:10.3390/agronomy12020329

Abstract

Ecklonia maxima and the commercial biostimulants produced from it contain various plant growth regulators that are responsible for the growth stimulation recorded in many crops. Auxins are one of the major plant growth regulators contained in E. maxima extracts. The aim of this research was to evaluate the growth-promoting effect of a seaweed extract from E. maxima on lettuce and tomato transplant production under nursery conditions, and to compare the effect of this extract with an equal concentration of synthetic auxin. Two doses of natural or synthetic exogenous auxins (50 or 100 μg L−1) were supplied to the substrate through the irrigation water with an ebb and flow system, 4, 11, and 18 days after sowing. A commercial biostimulant based on E. maxima extract was used as a source of natural auxin, while 1-naphthaleneacetic acid (NAA) was used as a synthetic auxin. Seedlings supplied only with water were used as a control. Tomato seedlings treated with 100 μg L−1 of natural auxins from E. maxima extract produced the tallest plants (+22%), with a higher leaf number (+12%), a wider leaf area (+44%), and a stronger stem (+12%), whereas lettuce seedling growth was promoted by all the treatments, but with a greater effect with increasing auxin supplementation and when using E. maxima extract, compared to NAA. The results showed that the supplementation of exogenous synthetic auxin (NAA), or an E. maxima extract containing natural auxins, can have a growth-promoting effect on lettuce and tomato seedlings. This effect was more evident on lettuce than tomato. The biostimulant produced from E. maxima extracts improved seedling quality and promoted shoot and root growth more than the NAA used as a synthetic source of auxins.

Highlights

One of the main goals of vegetable nurseries is to produce high-quality transplants in a short time
The results showed that the supplementation of exogenous synthetic auxin (NAA), or an E. maxima extract containing natural auxins, can have a growth-promoting effect on lettuce and tomato seedlings
The biostimulant produced from E. maxima extracts improved seedling quality and promoted shoot and root growth more than the naphthaleneacetic acid (NAA) used as a synthetic source of auxins

Summary

Introduction

One of the main goals of vegetable nurseries is to produce high-quality transplants in a short time. Transplants are commonly used for establishing crops in open fields and under greenhouses in many countries of the world [1], as they may determine many advantages during crop growth and improve vegetable production [2,3,4,5] These benefits can be closely related to the management of the seedlings during early growth (irrigation, fertilization, climatic conditions) [1,6,7,8,9] and their quality characteristics (e.g., height, leaf number and area, dry matter content). Vegetable seedlings are generally raised in trays filled with a limited volume of substrates with low nutrient content In these conditions, fertilization allows the shortening of production time and the production of good quality transplants that can guarantee a good performance after transplanting. The use of fertilizers on plants raised in containers with limited volumes of substrates, subjected to daily irrigation, can have a negative impact on the environment [10]

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