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Photosynthetic Gas Exchange Characteristics, Leaf Area and Dry Matter Accumulation of Two Blackgram Cultivars

D.K. Biswas
Department of Agronomy, BSMRAU, Salna, Gazipur-1703, Bangladesh.

M. M. Haque
Department of Agronomy, BSMRAU, Salna, Gazipur-1703, Bangladesh.

A. Hamid
Department of Agronomy, BSMRAU, Salna, Gazipur-1703, Bangladesh.

M. A. Rahman
HRC, BARI, Joydebpur, Gazipur-1701, Bangladesh.

Abstract/ Executive Summary:

A pot experiment was conducted to evaluate the gas exchange, leaf area dynamics and dry matter accumulation of blackgram varieties namely BARImash-3 and BINAmash-1. The two blackgram varieties did not differ statistically in gas exchange characteristics, leaf area and dry matter accumulation over the growth stages. Blackgram showed highest photosynthesis rate at flowering stage, might be attributed due to higher leaf chlorophyll, higher stomatal and mesophyll conductance and lower intercellular CO₂ concentration, but the highest respiration rate was found at pod filling stage. Leaves of top canopy showed highest gas exchange characteristics followed by the leaves of middle canopy and then bottom canopy. Diurnally, photosynthesis increased gradually with increasing intensity of light and peaked at around noon then decreases. Photosynthesis showed strong correlation with leaf area and dry matter accumulation of blackgram.

Keywords: Gas exchange, Leaf area, Dry matter, Blackgram

Location: Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, Bangladesh

Start Date: 00-00-1999

End Date: 00-00-1999

Program Area: Crop-Soil-Water Management

Commodity: Black gram

Objectives:

To know the photosynthetic activity over the growth stages, gas exchange characteristics in leaves of different canopy layers and the time course of gas exchange characteristics of blackgram cultivars.

Methodology:

A pot experiment was conducted at experimental farm of Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, Bangladesh during summer season of 1999. The two blackgram varieties namely BARI mash 3 developed by Bangladesh Agricultural Research Institute and another BINA mash 1 developed by Bangladesh Institute of Nuclear Agriculture were selected as treatment variables for this experiment. The experiment was laid out in randomized 951 complete block design. The plants were grown in 12 liter pots containing soils prepared by mixing silty-loam and cowdung in 3 : 1 ratio. Three well-soaked seeds were sown in each pot and at trifoliate stage only one healthy seedling per pot was retained. The plant received N, P and K @ 40-60-40 kg per ha^-1. Half of N and full dose of P and K were applied as basal dose and rest half of N was applied as top dressed at vegetative stage. Intercultural operations such as weeding, mulching, irrigation, plant protection measures etc. were done as needed. Photosynthetic gas exchange was measured at six growth periods viz. vegetative stage (25 DAE) flowering stage (35 DAE), pod filling stage (45 DAE), early maturity stage (55 DAE), mid maturity stage (65 DAE) and late maturity stage (75 DAE) using a portable photosynthesis system (LiCOR-6200). Measurement of gas exchange was done. At each measurement, fully expanded young leaf from top of the canopy was selected and attached with the leaf chamber. Leaf chlorophyll, stomatal conductance, mesophyll conductance, intercellular CO₂ concentration and respiration were also recorded at each measurement. Measurements were performed from twelve individual plants at each growth period. For measurement of respiration, leaf chamber was covered with a thick black cloth in a way that no radiation was entered into sample leaf. The sample leaf was attached into the leaf chamber of the photosynthesis system and CO₂ evolution rates were recorded for respiration. Photosynthetic gas exchange characteristics were measured from leaves of top, middle and bottom layers of canopy of blackgram and also recorded diurnally. Leaf chlorophyll was measured by chlorophyll meter. Fifteen plants were sampled at each vegetative, flowering, pod filling and maturity stage. Leaf area per plant was measured using a leaf area meter. Plant parts were oven dried at 70⁰C for 72 h for weighing the dry mass. Data on different parameters analyzed statistically and means were compared by using F-test and LSD test when necessary.

Source of Information: Online Journal of Biological Sciences 1 (10): 951-954, 2001

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Blackgram showed highest photosynthesis rate at flowering stage, might be attributed due to higher leaf chlorophyll, higher stomatal and mesophyll conductance and lower intercellular CO₂concentration, but the highest respiration rate was found at pod filling stage. Leaves of top canopy showed highest gas exchange characteristics followed by the leaves of middle canopy and then bottom canopy. Diurnally, photosynthesis increased gradually with increasing intensity of light and peaked at around noon then decreases. Photosynthesis showed strong correlation with leaf area and dry matter accumulation of blackgram.

Knowledge Management: Journal