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Leaf Photosynthesis, Respiration and Associated Parameters of Some Modern and Traditional Rice Varieties

M S I Mamin
PSO
ARD, BRRI, Gazipur

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

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

N I Bhuiyan
Formar Director General

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

Abstract/ Executive Summary:

This study evaluates four modern and four traditional rice varieties in pots at the Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Salna, Gazipur, Bangladesh, during wet season 2000 to compare some modern and traditional varieties in relation to photosynthesis (Pn), respiration and specific potential leaf characteristics such as stomatal conductance, mesophyll conductance, specific leaf weight (SLW), leaf chlorophyll and leaf nitrogen content. Photosynthesis and respiration rates with associated parameters were measured at panicle initiation (PI), booting, flowering and dough stages using portable photosynthesis measuring system (LiCOR-6200). Yield and yield attributes were recorded. The modern variety (MV), BRRI dhan32 exhibited the highest flag leaf Pn among all the varieties at booting and flowering stages. But BRRI dhan32 showed lower Pn than other varieties at PI stage (on fully expanded top leaf) which might be attributed to the differences in characteristics of the leaves selected at PI and reproductive stages (flag leaf) in relation to leaf chlorophyll and nitrogen contents. The traditional variety, Bunsha exhibited better Pn at all the measuring stages than the other traditionals except Kamargachikon only at booting stage. Mesophyll conductance paralleled leaf Pn and BRRI dhan32 displayed much higher rate than those of the others from booting to flowering. Very strong linear positive relationship was observed between Pn and mesophyll conductance at different growth stages (R2=0.95-0.99). Varieties highly differed in stomatal conductance and the respiration rates were quite inconsistent at different successive growth stages. However, the respiration rates of three MVs such as BR10, BR11 and BRRI dhan32 declined sharply after booting, which is a good character of those varieties, contributing their maximum dry mass to grains. Among eight varieties BRRI dhan32 provided the highest grain yield and harvest index. The relationships between flag leaf N% at flowering and Pn at booting, flowering and dough stages were linear but gradually became weaker (R2=0.6, 0.5 and 0.3 respectively). Similar trends were observed in relationship between flag chlorophyll-a and Pn (R2=0.68, 0.65 and 0.40 respectively) and between flag chlorophyll-b and Pn (R2=0.71, 0.62 and 0.41 respectively) at booting, flowering and dough stages. The linear relationship between Pn at flowering and grain yield (R2=0.62) and filled grains hill^-1 (R2=0.52) reveals that the greater was the Pn, the higher was the grain weight and filled grains hill-1. Among the tested varieties, flag leaf of BRRI dhan32 was found more potential in respect of chlorophyll and nitrogen content and photosynthetic capacity. Mesophyll conductance might be one of the most potential attributes controlling the photosynthetic rate.

Keywords: Photosynthesis, Respiration, Modern and Traditional Rice Varieties

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

Start Date: 01-07-2000

End Date: 31-12-2000

Program Area: Crop-Soil-Water Management

Commodity: Rice

Objectives:

To compare photosynthesis and respiration characteristics of some modern and traditional rice varieties along with their associated parameters in relation to grain yield and biomass production. If there is any potential attribute that may be considered in the breeding programme to break the yield ceiling.

Methodology:

The experiment was conducted in pots following CRD with 4 replications at the Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Salna, Gazipur Bangladesh, during wet season, 2000. Four modern varieties (MVs) (BR10, BR11, BR22 and BRRI dhan32) developed by Bangladesh Rice Research Institute (BRRI) and four traditional varieties, BSMRAU germplasm code no. IPK3001 (Lalmota), IPK10002 (Bunsha), IPK1021 (Kamargachikon) and IPK3011 (Bashfulchikon) collected from Jhalakathi, Khulna and Chittagong districts of the country having diverse agro-ecological environments, were evaluated. The traditional varieties were selected mainly based on their wide cultivation in those areas during wet season. Thirty-six-day old seedlings were transplanted on 30 July 2000 at the rate of two seedlings per pot. Irrigation and other intercultural operations were uniformly done.Specific leaf weight (SLW) was determined as leaf weight/leaf area (mg cm-2) and chlorophyll a and chlorophyll b were determined as per Arnon (1949) and leaf nitrogen was determined as per Cataldo et al, 1974. Photosynthesis and respiration rates together with associated parameters were measured using the fully expanded upper most leaves at panicle initiation (PI) while the flag leaves at booting, flowering and dough stages using portable photosynthesis measuring system (LiCOR-6200) between 11.00 and 14.00 hrs at a uniform light intensity (around 1550 quantum) provided artificially in laboratory. At the time of measurement the maximum temperature ranged 29.71 -31.69 c and the minimum temperature ranged 19.20 -23.91 c and the relative humidity ranged 77.26-80.16% at 9.00 hrs and 53.90-70.38% at 14.00 hrs (Plant Physiology Division, BRRI, Gazipur, about five km from BSMRAU lab). 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 space) was calculated as CO₂ concentration in air - CINT and respiration rate (µ mol m^-2 S^-1) was recorded. Grain weight hill^-1 (g) and yield attributes were recorded. ANOVA and LSD were employed by statistical package IRRISTAT windows version 4.0, 1998.

Source of Information: BANGLADESH RICE JOURNAL 16(1):35-40,June 2012 ISSN 1025-7330 (Bangladesh Rice J.)

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Among the Pn contributing parameters, the mesophyll conductance of the leaf might be one of the most potential attributes controlling the photosynthetic rate. The higher was the mesophyll conductance of leaf, the higher would be the Pn. The flag leaf of BRRI dhan32 appeared as the best among eight varieties in relation to mesophyll conductance, chlorophyll a, chlorophyll b and N contents enhancing post-anthesis photosynthesis rate that ultimately contributed to higher grain weight (64.51g/hill) than those of other varieties (27.79-63.97g hill^-1).

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