บทคัดย่องานวิจัย

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Postharvest keeping quality of lettuce (Lactuca sativa L. var. capitata L.) - measurement and analysis of climatic factors and transpiration.

Linke, M.; Schreiner, M.;

Gartenbauwissenschaft Year: 1995 Vol: 60 Issue: 5 Pages: 202-211 Ref: 18 ref.

1995

บทคัดย่อ

Postharvest keeping quality of lettuce (Lactuca sativa L. var. capitata L.) - measurement and analysis of climatic factors and transpiration.

 

In a study aimed at determining the extent to which crop-specific area and shape parameters account for deviations in transpiration rate measured under identical conditions (air temperature, RH, air velocity, atmospheric pressure, direction of flow), field-grown lettuces of the cultivars Kagraner Sommer and Premian were harvested at various stages of development (from the rosette stage to the beginning of shoot elongation) and placed in cuvettes supplied with conditioned outside air. Six cuvettes, allowing measurements in 6 lettuces, and 1 reference cuvette were linked to integrated CO2 and H2O gas analysers combined with a multiplexer system for switching gas channels and a computer-aided data logging system with test-related sensors. The relationship between climatic effects and plant responses (CO2 and water vapour exchange) was established using mass and heat transfer mechanisms that took into account the influence of air temperature, RH, air velocity, atmospheric pressure, atmospheric compo

sition and radiation. The effect of climatic conditions on H2O gas exchange could be determined using the relationship between transpiration rate on the one hand and the active area of transpiration and characteristic shape factors on the other hand, while taking the varying morphology of lettuce into consideration. An average total resistance in the water vapour pathway of an individual lettuce which took into account the overlapping of leaves could be ascertained according to the morphology and defined active area of transpiration. With regard to the mass transfer of water vapour, it was therefore possible to record the influence of simultaneously acting climatic parameters on harvested lettuce while incorporating phenotypical variation. Also a new system for scoring quality of lettuce is introduced.