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Water-soluble Carbohydrates in Rice Shoots as Affected by Submergence Stress at Vegetative Stage

Md. Mosharaf Hossain
Department of Crop Botany, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Md. Alamgir Hossain
Department of Crop Botany, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Md. Juiceball Hassan
Department of Crop Botany, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Md. Masudul Karim
Department of Crop Botany, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Md. Habibur Rahman Pramanik
Department of Crop Botany, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Abstract/ Executive Summary:

Submergence stress is one of the most important constraints for the productivity of rice in Bangladesh. A pot experiment was conducted at the net house of the Department of Crop Botany, Bangladesh Agricultural University during Aman season from July 2018 to December 2018 to study the changes in water-soluble carbohydrates in rice plants during the submergence stress and the recovery. The experiment consisted of two factors—(i) rice cultivars (Binadhan-11 and Binadhan-12 as submergence tolerant and BRRI dhan49 as susceptible) and (ii) submergence stress (both control and submerged for 14 days at the vegetative stage). Submergence stress was imposed by dipping the pot-grown plants into a water tank about 90 cm depth of water for 14 days. After 14 days, plants were removed from the tank and grown in the net house. Samplings were done at 0, 5, 10, 14 and 40 days after submergence to measure the contribution of shoot reserves, leaf greenness and shoot dry mass for their survival. Tolerant rice cultivars Binadhan-11 and Binadhan-12 had higher initial soluble carbohydrates than the susceptible one, BRRI dhan49. Under the submerged conditions, the tolerant cultivars showed slow depletion of water-soluble carbohydrates compared to susceptible ones. Higher carbohydrate contents intolerant cultivars might act as buffer stock during submergence for their better survival and growth.

Keywords: Shoot reserves, Non-structural carbohydrates, Leaf greenness, Submergence stress, Recovery

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

Start Date: 00-07-2018

End Date: 00-12-2018

Program Area: Crop-Soil-Water Management

Commodity: Rice

Objectives:

To study clearly the NSC accumulation and utilization by rice plant during submergence stress at vegetative stage and during the recovery after desubmergence.

Methodology:

Experimentation: A pot experiment was conducted in plastic pots at the net house of the Department of Crop Botany, Bangladesh Agricultural University, Mymensingh during the period from July 2018 to December 2018. The experiment was laid out as two factorial (rice cultivars and submergence stress) Completely Randomized Design (CRD) with 6 treatments and 3 replications. Three rice cultivars used in the experiment were Binadhan-11 Binadhan-12 (tolerant) and BRRI dhan49 (susceptible). A total of 30 pots (10L) were prepared with soil mixed with well-decomposed cow dung (2:1). Each pot contained about 10 kg of soil and cow dung mixture. Fertilizers were applied as basal dressing as follows: Urea, TSP, MoP, Gypsum and Zinc = 0.75, 0.55, 0.25, 0.15, and 0.06 g pot⁻¹. Submergence stress was imposed by dipping pot-grown rice plants into a water tank full of water. The water tank was first partially filled with tap water of about 0.5 m height and half of the total pots of 20 days old rice plants were placed in the water of the tank one by one with much care, and then the tank was filled with water to submerge the plants completely. The light intensity of the tank water at 15 cm and 30 cm depth were measured as 65.72 and 47.32 μmol m⁻²s⁻¹, respectively by Light meter (Model: LI–250A, Licor Bio Sciences, USA). Furthermore, the light intensity of the outer atmosphere was 240 μmol m⁻²s⁻¹. Dissolved oxygen concentration in tank water was recorded by DO meter (HANNA Instrument, Intl.) and it was 10.50 ppm. The temperature of tank water was 30.8 °C. The height of the water level in the tank was kept constant by adding the required water twice a day during the submergence stress. After 14 days of submergence, the plants were removed from the water tank after draining the water from the tank using a siphoning pipe. The plants were grown with proper care after desubmergence for about a month as recovery. The control plants were maintained with sufficient water and management practices. Intercultural operations such as irrigation, weeding and spraying of pesticides were done as and when necessary to ensure normal growth. Sampling and measurements: Three hills of each cultivar were sampled at 0, 5, 10, 14 and 40 days after submergence. The shoots were dried in an oven at 80 °C for 3 days and were weighed to get shoot dry mass (DM) and then stored for the measurement of water-soluble carbohydrates (WSCs) using the anthrone method (Yemm and Willis, 1954). The Leaf greenness of the fully expanded uppermost leaves was measured on different sampling dates during submergence and recovery in all cultivars with a chlorophyll meter (SPAD–502; Konica Minolta Sensing Inc., Osaka, Japan). SPAD readings were taken at three positions (near base, near apex and middle) of the leaf immediately after the sampling for shoot DM and WSCs, and were averaged for each leaf. Three leaves were measured and the readings were averaged for a pot. Estimation of water-soluble carbohydrates (WSCs): The WSCs in shoots were extracted and measured using the anthrone method (Yemm and Willis, 1954) as described by Hossain et al. (2011). The dried shoots were milled to be rough powder after chopping for a while. The first extraction was done with some weighed powder with 80% ethanol at 60°C for 30 min and the 2 successive 15–min extractions were done with distilled water. The extracts were combined and evaporated to dryness at 65°C. The dried carbohydrates were then resolved in 5 mL distilled water and a fraction of the extract solution (about 1 ml) was taken in a micro-centrifuge tube (1.5 mL) with charcoal powder. Powder and extract solution were mixed with a vortex (touch mixer) and then the solution was centrifuged at 5000 rpm for 5 min to make the solution clear. Then the solutions were diluted 10 times with distilled water and the diluted solution (0.1 ml) was mixed with an ice-cold anthrone reagent (5 mL). After heating for 10 min in a boiling-water bath and subsequently cooling with ice water, the absorbance reading was taken with a spectrophotometer at 620 nm. The content of WSCs in the sample was calculated as mg WSCs per gram of shoots dry mass using regression equation and the amount of WSCs in shoots was estimated based on the dry mass of shoots (Ehdaie et al., 2006). Statistical analysis: All data were analyzed statistically using MS Office Excel application. Data were analyzed by calculating means and standard errors of means (SEM).

Source of Information: J Bangladesh Agril Univ 18(S1): 788–794, 2020 ISSN 1810-3030 (Print) 2408-8684 (Online)

Article Link (Online Journal): https://doi.org/10.5455/JBAU.17313

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The Carbohydrate content of all three rice cultivars decreased with the increase of submergence duration. Maximum reduction in carbohydrate content due to submergence stress was noted in susceptible cultivar BRRI dhan49 under 14 days of submergence. However, tolerant rice cultivars had high initial water-soluble carbohydrate and lower percent reduction in soluble carbohydrate during submergence and thereby it may be said that higher water-soluble carbohydrate could be beneficial for survival during submergence.

Knowledge Management: Journal