Effect of Wastewater Irrigation on Photosynthesis, Growth, and Anatomical Features of Two Wheat Cultivars (Triticum aestivum L.)

Shokoofeh Hajihashemi,Marzieh Raeisi,Sonia Mbarki,Milan Skalicky,Marian Brestic,Fariba Noedoost

doi:10.3390/w12020607

Abstract

The wastewater from the Razi petrochemical complex contains high levels of salts and heavy metals. In the present research, the effects of different wastewater dilution levels (0, 25%, 50%, and 100%) were studied on two wheat cultivars—Chamran and Behrang. The wastewater contained high levels of NH4+, NO3-, PO43-, and SO42-, and Mg, Ca, K, Na, Cu, Zn, Fe, M, and Ni. The toxic levels of mineral elements in the wastewater resulted in a significant decline in the K, P, Si, and Zn content of leaves. Irrigation with the wastewater resulted in a significant reduction in photosynthetic characteristics including chlorophyll fluorescence (Fv/Fm and PIABS), intercellular CO2, net photosynthesis, water use efficiency, and photosynthetic pigments. The reduction in photosynthesis was followed by a significant decrease in the carbohydrate content and, subsequently, plant height, leaf area, and grain yield. Increasing the wastewater concentration reduced leaf thickness and root diameter, accounting for the decrease in xylem and phloem vessels, the root cortical parenchyma, and mesophyll thickness. The bulliform cell size increased under wastewater treatment, which may suggest induction of a defense system against water loss through leaf rolling. Based on the observed negative effect of wastewater on physiology, morphology, anatomy, and yield of two wheat cultivars, reusing wastewater with high levels of total suspended solids and salts for irrigation cannot be approved for wheat crops.

Highlights

With the global shortage of water, major attention has been paid to reusing wastewater for irrigation of various crops
The data of the present study showed that grain filling decreased in wastewater-irrigated plants, which could be explained by impaired photosynthesis resulting in reduced carbohydrate biosynthesis and abnormalities in phloem vessels of leaves that inhibited translocation to the sink organ
Wheat irrigation with untreated wastewater from the Razi petrochemical complex decreased the photosynthetic characteristics, nutrient concentrations, and carbohydrates, which resulted in reduction in growth

Summary

Introduction

With the global shortage of water, major attention has been paid to reusing wastewater for irrigation of various crops. Depending upon the source of wastewater, it may contain high concentrations of salts and heavy metals. The high concentrations of salts may adversely affect physiological processes and growth of wastewater-irrigated plants, especially salt-sensitive. The petrochemical operations produce a vast quantity of wastewater contaminated with different salts and heavy metals [2,4]. The wastewater produced by the petrochemical industry was found to be contaminated with a variety of toxic pollutants such as heavy metals [5,6,7] and using it for crop irrigation led to lower plant biomass and yield [1,8,9]. There are some mineral elements which are critical for growth of crop plants and reduction of their concentrations from optimum levels impairs plant health and lowers yield [14]

Methods

Results

Discussion

Conclusion