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Changes in Spad Value and Soluble Carbohydrate Concentration During Senescence of Wheat Flag Leaf Under Heat-stressed Environment

M. MOHI-UD-DI N
Department Crop Botany, Bangabandhu Sheikh Mujihur Rahman Agricultural University, Cazipur

M.A. RAH MAN
Department Crop Botany, Bangabandhu Sheikh Mujihur Rahman Agricultural University, Cazipur

J. U. A HMED
Department Crop Botany, Bangabandhu Sheikh Mujihur Rahman Agricultural University, Cazipur

Abstract/ Executive Summary:

An experiment was conducted with two wheat cultivars showing different cell membrane thermostability viz. a relatively heat tolerant Kanchan and a heat sensitive Sonora to compare senescence of wheat flag leaf induced by heat-stressed environment in terms of SPAD value and soluble carbohydrate level. Results clearly revealed that the onset of flag leaf senescence was indicated by the SPAD value just below 30 and by the highest level of soluble carbohydrate accumulation in flag leaf irrespective of cultivars and environmental variations. Under heat-stressed environment, the onset of flag leaf senescence commenced at 5 days earlier compared lo normal environment in Sonora while in Kanchan such change was absent. The present results suggest that the senescence of flag leaf was forced by heat-stressed environment and forcing being less pronounced in Kanchan expressing its greater heat-stress tolerance than that of Sonora. The SPAD value and soluble carbohydrate concentration were strongly correlated and the correlation between them was similar (poly nominal) for both . wheat cultivars under both growing environments.

Keywords: Senescence, Membrane thermostability, Heat-stress , Soluble carbohydrate

Location: Gazipur

Start Date:

End Date:

Program Area: Knowledge Management

Commodity: Wheat

Objectives:

The objective of this study was to evaluate the late planting induced senescence of wheat flag leaf through investigating the changes in SPAD value and soluble carbohydrate levels in two wheat cultivars differing in membrane thermostability.

Methodology:

The experiment was carried out at thc research farm of Bangabandhu Sheikh Mujibur Rahman Agricultural University ( BSMRA U). Gazipur , Bangladesh during November 2001 to April 2002 on an upland soil. Two wheal cultivars. Kanchan (a late. H Y V and extensively cultivated cultivar) and Sonora (an early cultivar). were used as seed materials . A fertilizer dose of 100-38-25-20 kg/ha N , P, K and S was applied in the form or urea , triple supper phosphate (TSP), muriate of potash ( M P) and gypsum , respectively. Membrane thermostability ( M T) test: MT was measured by relative electrolyte leakage through cell membrane at elevated temperature of 55°C following the procedure of . Hossain et al. ( 1995). SPAD reading: At anthesis, 50 plants were tagged from each treatment plot. Five wheat plants were. selected from each plot for one reading . SPAD value was taken from middle portion of the specified flag leaf at 5-day intervals using Minolta chlorophyll meter ( Model: SPAD-502, Minolta Co. Ltd., Japan) . Measurements at each leaf consisted average or 5 readings. Soluble carbohydrate estimation: The same leaves were harvested at the same day. The samples were kept in oven at 70°C for 72 hours and were ground finely in mortar and pestle. Then the soluble carbohydrate content of flag leaf was determined using the Anthrone method described by Yoshida et al. (1975).

Source of Information: J. Asiat. Soc. Bangladesh, Sci., 33(2): 121 -130, December 2007

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Onset of flag leaf senescence occurred at a SPAD value just below 30, and SC concentration at those SPAD values denoted as a threshold soluble carbohydrate level. The threshold flag leaf soluble carbohydrate level did not appear to differ between wheat cultivars (I06.77 vs. l 04.5 mg/g LDM ) under normal environment, but it was found to differ significantly ( 129.4 vs. 121 .19 mg/g LDM) due to heat-stressed environment.

Knowledge Management: Journal