Effect of potassium fertilizer on the growth, physiological parameters, and water status of Brassica juncea cultivars under different irrigation regimes.

Preeti Rani,Narender Singh,Ishan Saini,Prashant Kaushik,Hadeer Darwish,Amal Al-Barty,Leonard Wijaya,Ahmed Noureldeen

doi:10.1371/journal.pone.0257023

Abstract

Abiotic stress, especially a lack of water, can significantly reduce crop yields. In this study, we evaluated the physiological and biochemical effects of potassium sulfate (K2SO4) fertilizer and varied irrigation regimes on the economically significant oilseed crop, Brassica juncea L, under open field conditions. Two cultivars (RH-725 and RH-749) of B. juncea were used in a randomized complete block design experiment with three replicates. Irrigation regimes consisted of a control (double irrigation: once at the 50% flowering and another at 50% fruiting stages), early irrigation (at 50% flowering only), late irrigation (at 50% fruiting only) and stress (no irrigation). The K2SO4 applications were: control (K0, no fertilization); K1, 10 kg ha−1; and K2, 20 kg ha−1. We measured growth via fresh and dry plant weight, plant height, root length, and leaf area. All the growth parameters were higher in RH-749. The physiological attributes, including the membrane stability index and relative water content, were higher at the 50% flowering stage in RH-749. The amount of antioxidant enzymes (catalase (CAT), guaiacol peroxidase (POX), ascorbate peroxidase (APX), and superoxide dismutase (SOD)) was enhanced when both plants were fertilized during water stress. All of these enzymes had higher activity in RH-749. The total chlorophyll content and photosynthesis rate were considerably higher in RH-749, which leaked fewer electrolytes and maintained a less destructive osmotic potential under limited water conditions. The results indicated that it is water-stress tolerant when given a high concentration of K2SO4, which alleviated the adverse effects of water stress on growth and physiology.

Highlights

MethodsThe field experiment was carried out from October to March 2018–2019 and 2019–2020 at a nursery in Kurukshetra University, Kurukshetra, India (29 ̊95’N; 76 ̊82’E)
To understand how the plants respond to stress, we evaluated the antioxidant defence system comprising peroxidase (POD), ascorbate peroxidase (APX), superoxide dismutase (SOD), and catalase (CAT)
The higher application rate of K2SO4 significantly improved the morphological traits of both B. juncea cultivars under low water conditions, including water stress

Summary

Methods

The field experiment was carried out from October to March 2018–2019 and 2019–2020 at a nursery in Kurukshetra University, Kurukshetra, India (29 ̊95’N; 76 ̊82’E). Nighttime temperatures averaged 30 ± 4 ̊C and 20 ± 5 ̊C, respectively. The experiment was designed as a randomized complete block with a factorial treatment structure in three replicates. The four irrigation regimes induced water stress by withholding irrigation during a vital development stage (siliquae (fruit) development and flower initiation). It consisted of: control (irrigated twice, at the 50% flowering and 50% siliquae formation stages), late stress (once at 50% flowering), early stress (once at 50% siliquae formation), and total stress (no irrigation)

Results

Discussion

Conclusion