# Photosynthetic responses of hydroponically grown basil (Ocimum basilicum L.) to drought and high-EC stress

## TL;DR

This study explores how drought and high salt levels affect basil's photosynthesis in a hydroponic system, revealing distinct stress responses detectable through chlorophyll fluorescence.

## Contribution

The study identifies differential physiological responses to drought and high-EC stress in basil using chlorophyll fluorescence techniques.

## Key findings

- High EC stress caused a wider range of changes in Photosystem II parameters compared to drought stress.
- Mature basil plants showed greater tolerance to stress, likely due to more efficient electron transport and structural stability.
- Chlorophyll fluorescence measurements effectively detected distinct physiological responses to the two stressors.

## Abstract

Basil (Ocimum basilicum L.), a widely cultivated culinary and medicinal herb in the Lamiaceae family, is particularly vulnerable to various environmental stressors. This study examines how water deficit and elevated nutrient-solution electrical conductivity (EC) affect the photosynthetic efficiency of basil plants grown in an nutrient film technique (NFT) hydroponic system.

Chlorophyll fluorescence was assessed using both continuous-excitation and modulated pulse-amplitude-modulated (PAM) techniques. Fluorescence parameters were monitored in plants at two developmental stages, immature and mature, under drought and high–electrical-conductivity (EC) stress.

Both stressors altered Photosystem II (PSII)—related fluorescence parameters, but high EC stress caused a wider spectrum of changes. In mature plants, those alterations were less pronounced, indicating enhanced tolerance likely due to more efficient electron transport and greater structural stability of the photosynthetic apparatus. The obtained results supported our hypothesis, that drought and high-EC stress would differentially impair photosynthetic efficiency, with drought imposing stronger osmotic limitations on photochemistry and high EC introducing additional ionic constraints. These stresses generated distinct physiological response patterns detectable by chlorophyll fluorescence measurements.