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Effect of Post-anthesis Drought on Photosynthesis, Respiration and Associated Parameters of Modern and Traditional Rice Varieties

M S I Mamin
PSO
Adaptive Research Division, BRRI, Gazipur 1701, Bangladesh

A Hamid
Professor
Department of Agronomy, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Salna, Gazipur 1706.

M M Haque
Professor
Department of Agronomy, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Salna, Gazipur 1706.

N I Bhuiyan
Former Director General, BRRI

A Karim
Professor
Department of Agronomy, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Salna, Gazipur 1706.

Abstract/ Executive Summary:

This study evaluates one modern (BR22) and two traditional rice varieties (Lalmota and Matichal) in pots at Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Salna, Gazipur, Bangladesh, during T. Aman 2000 to measure photosynthesis (Pn), respiration and associated parameters such as leaf water potential, leaf water content, stomatal conductance, mesophyll conductance under post-anthesis drought at milky and dough stages. Portable photosynthesis measuring system (LiCOR-6200) was used in laboratory. Yield and yield attributes were recorded. Water stress markedly reduced Pn. BR22 displayed larger Pn than two traditional varieties under both optimal irrigated and post-anthesis drought conditions. Mesophyll conductance was also drastically reduced due to drought and paralleled Pn. However, stomatal conductance was slightly affected by drought. Leaf intercellular CO₂ concentration became higher under post-anthesis drought because of less utilization of CO₂for Pn and hence diffusion pressure deficit from air to leaf intercellular spaces was decreased. However, BR22 maintained higher diffusion pressure deficit than traditional varieties, because it was able to run its Pn more actively than the traditional varieties by maintaining its better mesophyll conductance even at drought. Drought did not alter leaf respiration rate appreciably and were inconsistent among the varieties. Leaf water potential in three varieties were significantly decreased due to drought. BR22 maintained relatively higher than Lalmota and Matichal. Leaf water content (%) paralleled . Pn had positive and linear association with leaf water potential (R2=0.91-0.98). Mesophyll conductance also had positive and linear association with Pn (R2=0.97- 0.99). But the relationship between stomatal conductance and Pn was weak and inconsistent (R2=0.04-0.45). Averaged over the varieties, drought caused a grain yield reduction of 57.50%. Drought significantly reduced the number of filled grains per panicle, increased sterility percentage, reduced the grain size (1000 grain weight), straw yield and HI.

Keywords: Post-anthesis, Drought, Photosynthesis, Respiration, Modern and Traditional Rice Varieties

Location: Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Salna, Gazipur

Start Date: 00-07-2000

End Date: 00-12-2000

Program Area: Risk Management in Agriculture

Commodity: Rice

Objectives:

To evaluated the photosynthesis and respiration along with their associated parameters of modern and traditional rice varieties under post-anthesis drought to identify potential attributes controlling photosynthesis and respiration.

Methodology:

The experiment was conducted in pots with five replications at the Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Salna, Gazipur. Fertilizers were applied in the soil of the pots @ 80:60:40:10:3 kg N, P₂O₅, K₂O, S Zn ha^-1 (1 ha soils = 2 × 106 kg) respectively, as urea, triple super phosphate (TSP), muriate of potash (MP), gypsum and zinc sulphat (ZnSO₄). Except urea, all the fertilizers were uniformly mixed in the soil before filling the pots. The urea was uniformly top-dressed in four equal splits up to panicle initiation stage.We evaluated two traditional varieties, Lalmota (BSMRAU germplasm Acc no. IPK3001) and Matichal (BSMRAU germplasm Acc no. 3003) and one modern variety, BR22, developed by BRRI, Gazipur. All three varieties were late maturing and selected to represent the varieties those usually encounter water stress during post-anthesis period. Two seedlings per pot were grown under uniform management and cultural conditions. At heading stage pots were grouped into two. For measuring photosynthesis, one group of plants comprising five pots for each variety (5 × 3 varieties=15 pots) was continued with irrigation water, while irrigation was withheld in another group having same number of pots after heading and excess water was removed. In addition, four extra pots for each variety under each group were treated alike and used for destructive sampling to measure leaf water content, leaf water potential and soil moisture content over time.The data recorded were net photosynthetic rate (µ mol m^-2 s^-1), stomatal conductance (mol m^-2 s^-1), leaf intercellular CO₂ concentration (CINT) (ppm), mesophyll conductance (mol m^-2 s^-1), as Pn/CINT (Kubota and Hamid, 1992), CO₂ concentation gradient or diffusion pressure deficit (DPD) (the driving force from air to leaf intercellular spaces) was calculated as CO₂ concentration in air-CINT, and the Respiration rate (µ mol m^-2 s^-1). Grain weight hill^-1 (g), straw weight hill^-1 (g), filled grains panicle^-1, sterility %, 1000-grain weight and harvest index were recorded following the standard methodologies. Analysis of variance (ANOVA) of concerned variables was performed using IRRISTAT windows version 4.0 (1998) and means separated by LSD.

Source of Information: Bangladesh Rice J.16(1):11-22, June 2012, ISSN 1025-7330

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Post-anthesis drought markedly reduced grain yield irrespective of modern and traditional varieties. Reduction of photosynthesis rate due to drought is one of the vital causes for lower grain yield at terminal drought. Stomatal conductance was slightly affected but mesophyll conductance was severely affected and hence mesophyll conductance was found as the major determinant for reduction in photosynthesis rate under drought. Both modern and traditional varieties were not able to minimize their respiration rates. However, BR22 has some genetic potential to maintain relatively higher mesophyll conductance than traditional varieties even under drought. So, more studies should be conducted using more late maturing modern and traditional varieties to identify potential genotypes having capability of maintaining higher mesophyll conductance at post-anthesis drought in order to use in the breeding programne for developing drought resistant varieties.

Knowledge Management: Journal