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#biomass measurement

2 public questions tagged with this topic.

Plant tissue culture 1

Growth index of callus culture is calculated using:

Growth index measures proliferative performance of callus cultures quantitatively allowing comparison across media treatments hormone combinations and genotypes. Most accurate method utilizes change in dry weight rather than fresh weight or visual scoring because fresh weight is confounded by variable water content due to hyperhydricity, extracellular polysaccharide secretion, and vacuolar water uptake that fluctuates with osmolarity of medium. Dry weight determination involves harvesting callus, washing to remove agar, oven drying at 60 to 80 degrees Celsius to constant mass eliminating moisture, weighing analytical balance. Index calculated as final dry weight minus initial inoculum dry weight divided by initial dry weight multiplied by 100 percent, or sometimes as ratio of final to initial. This metric reflects true biomass accumulation including cell number increase and deposition of cell walls proteins and starch. Cell number counting is impractical in clumpy callus requiring enzymatic dissociation inducing error. Monitoring dry weight growth curve shows lag exponential stationary phases and correlates with metabolic activity secondary metabolite yield and requirement for timely subculture every 3-4 weeks preventing nutrient depletion and phenolic browning.

Ref: Bhojwani & Razdan 1996 growth indices; Plant Cell Culture protocols dry weight method.

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Ecosystem Pyramid

In which pyramid is dry weight used as the measurement unit?

A biomass pyramid quantifies the mass of living material at each trophic level, commonly as dry mass per unit area or volume. Drying removes variable water content, making tissue quantities more comparable among organisms and habitats. Biomass remains a standing stock and should not be confused with productivity, which is biomass generated per unit time. Slow-growing trees can create a large standing biomass, whereas rapidly renewed phytoplankton may have low biomass despite high annual production. Energy and matter should not be conflated: nutrients can cycle among levels, but respiratory heat cannot be recycled into chemically useful energy by the community. Pyramid shape is an accounting result with biological causes, including body-size distributions, tissue longevity, consumption, assimilation, respiration, and population turnover. A snapshot may differ seasonally, especially in plankton or annual vegetation, whereas integrated production better represents ecosystem functioning across time. The ten-percent heuristic is useful for prediction but not exact; empirical transfer efficiencies vary with food quality, ectothermy, producer defenses, and detrital routing.

Ref: Fundamentals of Ecology, Odum & Barrett, 5th Ed., Ch. 3

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