Effects of green seaweed extract on Arabidopsis early development suggest roles for hormone signalling in plant responses to algal fertilisers

Fatemeh Ghaderiardakani,Juliet C Coates,Neil S Graham,Deborah Kohn Damiano,Katherine Tagg,Ellen Collas

doi:10.1038/s41598-018-38093-2

Fatemeh Ghaderiardakani, Juliet C Coates + Show 4 more

Open Access

https://doi.org/10.1038/s41598-018-38093-2

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Abstract

The growing population requires sustainable, environmentally-friendly crops. The plant growth-enhancing properties of algal extracts have suggested their use as biofertilisers. The mechanism(s) by which algal extracts affect plant growth are unknown. We examined the effects of extracts from the common green seaweed Ulva intestinalis on germination and root development in the model land plant Arabidopsis thaliana. Ulva extract concentrations above 0.1% inhibited Arabidopsis germination and root growth. Ulva extract <0.1% stimulated root growth. All concentrations of Ulva extract inhibited lateral root formation. An abscisic-acid-insensitive mutant, abi1, showed altered sensitivity to germination- and root growth-inhibition. Ethylene- and cytokinin-insensitive mutants were partly insensitive to germination-inhibition. This suggests that different mechanisms mediate each effect of Ulva extract on early Arabidopsis development and that multiple hormones contribute to germination-inhibition. Elemental analysis showed that Ulva contains high levels of Aluminium ions (Al3+). Ethylene and cytokinin have been suggested to function in Al3+-mediated root growth inhibition: our data suggest that if Ulva Al3+ levels inhibit root growth, this is via a novel mechanism. We suggest algal extracts should be used cautiously as fertilisers, as the inhibitory effects on early development may outweigh any benefits if the concentration of extract is too high.

Highlights

Plant growth, development and productivity is affected by various abiotic and biotic factors
The final germination percentage was reduced in 0.8% and 1.0% Ulva extract: only about half the seeds germinated in 1.0% Ulva extract after a week (Fig. 1a)
Ulva extract at concentrations of 0.5–1% inhibits wild-type Arabidopsis seed germination

Summary

Introduction

Development and productivity is affected by various abiotic (physical) and biotic (biological) factors. Responses to these factors determine cropping pattern and plant distribution[1]. The frequency of abiotic environmental stresses (flooding, drought, water limitation, salinity and extreme temperatures) is increasing[4] and causing crop losses worldwide[5,6,7]. Applying seaweeds/seaweed extracts in modern agriculture leads to increased seed germination rates, improved plant development Seaweed fertilisers have been used in agricultural programs to improve soil- and disease-management, nutritional strategies, water efficiency and drought tolerance[23]. Depending on whether algal extract is applied as liquid fertiliser or seaweed manure to plant roots, or as a leaf spray, different plant responses to seaweeds occur[14,21]

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