Root exudation rates of three leafy vegetables under different light qualities

Vertical farming may increase the diversity of ways to produce food.
Within vertical farms, many environmental factors can be controlled for optimum growth conditions.
While the effects of these environmental factors are relatively well-understood for their impact on aboveground growth, very little is known about belowground processes.
In this article, we will study the effects of light quality, and specificly monochromatic red light on the root exudation of three leafy vegetables: lettuce, arugula and watercress.
Plants were grown in deep flow culture, and exudate was collected 24 days after transplanting.
Total exudation rates of C, carbohydrates and phenolics were determined spectrophotometrically.
Red light significantly (p<0.05) increased the total C exudation rate for the three leafy vegetables.
The carbohydrate exudation rate tended (p<0.1) to be higher for watercress, compared to lettuce and arugula.
The phenolic exudation rate of watercress was three- to four times higher than that of lettuce or arugula, respectively.
Moreover, the relative contribution of unidentified metabolites increased with red light.
So, red light changes exudation rates in leafy vegetables both quantitatively and qualitatively.
It seems that carbohydrate exudation rates are stable in leafy vegetables in deep flow culture.
The exudation rate of phenolics is species dependent, but the total exudation rate is light quality dependent.

EHC2024: International Symposium on Urban Horticulture: from Vertical Farming to Planting Design

B.R. de Haas, A. Indeche, D. Geelen, E. Dhooghe

root exudate, hydroponics, leafy vegetables, light quality

https://doi.org/10.17660/ActaHortic.2025.1441.6