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Salinity in the First Phase of Salt Stress Alters Photo-physiology, Water Use Efficiency and Total Soluble Phenolics of Maize Genotypes

Md. Injamum-Ul-Hoque
Department of Agriculture, Bangabandhu Sheikh Mujibur Rahman Science and Technology University, Gopalganj, Bangladesh

Md. Nesar Uddin
Department of Crop Botany, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Marzana Akter
Department of Crop Botany, Khulna Agricultural University, Khulna 9100, Bangladesh

Md. Rasel
Department of Genetics and Plant Breeding, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Md. Abdullah Al Bari
Department of Genetics and Plant Breeding, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Abstract/ Executive Summary:

Salinity is one of the most important abiotic stresses that adversely affects plant growth and development around the world. In order to elucidate the growth and physiological responses of maize genotypes under the first phase of salt stress (12 dS m-1 for two weeks), we investigated some growth and physiological traits at vegetative stage (28 d old plant) of four maize genotypes, namely indigenous yellow pure line, indigenous yellow, hybrid, and indigenous white. Salt stress significantly reduced shoot height and stem diameter in almost all genotypes. Under salt stress, instantaneous water use efficiency was highly increased in indigenous yellow pure line (285.5%), in contrast it was decreased significantly in hybrid (16.99 %) genotype compared to their respective control. Photosynthesis rate (70−87%), transpiration rate (81−91%), and stomatal conductance (80−92%) were significantly reduced due to salinity in all the tested genotypes. In the younger shoot, total phenolics content increased significantly in the young shoots of hybrid (42.26 %) and indigenous yellow pure line (40.03 %) genotypes under the first phase of salt stress. In contrast, there was no significant influence of salinity on total phenolics content of older shoot fraction in any genotype tested. Apparently, the growth and physiological traits were hampered in the first phase of salt stress in all tested genotypes. However, deposition of soluble phenolics under salt stress was genotype and leaf-region specific. As the most traits studied were highly influenced by the salinity in the first phase of salt-stress among genotypes at vegetative stage, breeders can potentially use these traits further in breeding program for the development of maize genotypes tolerant to the salt-stress at the vegetative stage of growth.

Keywords: Salinity, Photosynthesis, Transpiration, Stomatal conductance, Phenol

Location: The net house of the Department of Crop Botany, Bangladesh Agricultural University, Mymensingh, Bangladesh

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Maize, Water salinity

Objectives:

To determine the salt-stress response of four maize genotypes to moderate salinity level at the early vegetative growth stage to investigate in terms of growth traits, gas exchange parameters.

Methodology:

Plant materials and experimental layout Four maize genotypes namely indigenous yellow pure line (IYPL), indigenous yellow (IY), hybrid, and indigenous white (IW) were used as plant materials in this study. The pot experiment was conducted in net house of the Department of Crop Botany, Bangladesh Agricultural University, Mymensingh, followed by a completely randomized design (CRD) with four replications. Two levels of salinity (control: without addition of NaCl and salinity: addition of NaCl to reach EC 12 dS m-1 ) were tested against each genotype. Plant cultures and salinity stress imposition Maize caryopses were sterilized with Vitavax 0.2% followed by proper washing with water. Afterwards, caryopses were soaked in the aerated water overnight. Four seeds of each genotype were placed into the 10 L plastic container that was filled with 12 kg air-dried subsoil fertilized with standard fertilizer doses and water content inside the pot was adjusted to 60% of total water holding capacity (WHC) by adding water. After 4 days of germination, only one healthy seedling was kept in each pot. After 10 days of seedling establishment, the salinity treatment was applied by means of adding NaCl in four consecutive days employing one fourth amount of NaCl (EC- 3 dS m-1 ) in each time to reach a final EC of 12 dS m^-1 . The first and the last salt-stress imposition took place on the day 11th and 14th, respectively after seeding. Afterwards, plants were grown in this saline environment for next 14 d without further addition of salt. The control plants were grown without the addition of NaCl. Determination of photophysiological parameters and water use efficiency Net photosynthetic rate (A), transpiration rate (E) and stomatal conductance (gs) were recorded from the fully expanded 8th leaf of 27 days old maize plant using a portable photosynthesis system (LCi-SD System, ADC Bioscientific Ltd., Hoddesdon, UK) (Abbasi et al., 2015). Afterwards, IWUE was calculated by dividing the net photosynthetic rate (A) with the transpiration rate (E) following the method of Dias et al. (2017). Determination of phenolic content To analyse the phenolics content of shoot, 8th and above order leaves were separated from the rest. The basal 10 cm of these leaves were separated being younger shoot and the rest above parts of these leaves without basal 10 cm were kept being older shoot. Fresh leaf tissue (50 mg) from each fraction of leaves was homogenized with methanol for 2 min by OV-5 homogenizer [Modified from Albano and Miguel (2011)]. Then, some extracts were centrifuged at 14,000 g in a vial for 5 min and afterwards, extracted liquid samples mixed with FolinCiocalteau’s phenol reagent in a test tube. Then, 10% sodium bicarbonate solution (NaHCO3) were added and allowed 30 min in dark condition. Finally, the absorbance was recorded at 760 nm by using DR-6000 spectrophotometer. Gallic acid standard was prepared by diluting appropriate amount of analytical grade gallic acid to the methanol and results were expressed as mg phenol as gallic acid equivalent/100 g of leaf fresh mass. Data analyses Data were subjected to t-test in Microsoft Excel 10 to realize any difference between the salt stress and the control treatments. Data presented in the graphs were processed in GraphPad Prism 8.

Source of Information: J Bangladesh Agril Univ 19(1): 14–21, 2021 ISSN 1810-3030 (Print) 2408-8684 (Online)

Article Link (Online Journal): https://doi.org/10.5455/JBAU.46043

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

All growth parameters viz., shoot length and stem diameter of maize plants were negatively influenced by salinity in the present study. The parameters mentioned before were declined more or less in all maize genotypes. Gas exchanges parameters like net photosynthesis rate, rate of transpiration and stomatal conductance of CO2 were decreased in all the tested maize genotypes after exposing to full strength of NaCl stress for 14 days. But salinity caused increment in instantaneous water use efficiency, in indigenous yellow pure line. In response to the salinity, total alcohol soluble phenolics were increased significantly in indigenous yellow pure line and hybrid genotypes but only in the younger shoot fraction (basal 10 cm of 8th and above order leaves) In contrast, older shoot (8th and above order leaves without basal 10 cm) did not show any significant change in total soluble phenolics due to salinity. Thus, it is be concluded that all the parameters studied here were greatly influenced under first phase of salt stress and can be used for further screening purposes to identify salt resistance genotype for our future demand of food supply.

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