Response of anatomical traits to environmental stresses in the leaves of local orange seedlings (Citrus sinensis L)

Abstract

This study explores the effects of salinity and drought stress on the anatomical characteristics of local orange seedlings. The research was conducted at the Agricultural Research Station of the College of Agriculture, University of Basra, during the 2022-2023 agricultural season. Salinity stress was imposed using three concentrations of irrigation water (0, 3, and 6 ds.m-1), while drought stress was implemented by varying irrigation frequency (daily, weekly, and monthly). The anatomical traits examined included cuticle layer thickness, epidermal cell thickness, mesophyll cell diameter, vascular bundle diameter, tannin cell diameter, and vascular bundle sheath thickness. A recent study found that salinity stress in irrigation water and drought have a negative impact on the anatomical characteristics of local orange seedlings. Salinity (6 ds/m) and drought (monthly irrigation) led to an increase in the thickness of the cuticle layer (2.50 and 2.03 µm) and the diameter of the tannin cells (7.74 and 6.67 µm). These treatments also caused a decrease in the thickness of the epidermal cells, the diameter of the cells of the mesophyll tissue, the vascular bundle, and the thickness of the sheath of the vascular bundle. The study also found that the interaction between salinity stress and drought led to an even greater decrease in the anatomical characteristics of the seedlings. The interaction between salinity (6 ds/m) and drought (monthly irrigation) caused a decrease in the thickness of the epidermal cells, the diameter of the cells of the mesophyll tissue, the vascular bundle, and the thickness of the sheath of the vascular bundle to 2.57, 5.40, 33.23, and 20.11 µm, respectively. Keywords: Anatomical characteristics, drought, environmental stresses, orange seedlings, salinity