Experimental reagent
Trichloroacetic acid, paraffin wax.
Scissors, analytical balances, weighing dishes (or aluminum boxes), ovens, blades, metal (plexed glass) templates (or punchers), gauze, clips, covered enamel plates, tin foil, etc. 1. Select the measurement sample: The experiment can start from 8:00 am to 9:00 am on the sunny day, and select 10 representative leaves (such as the leaf on the plant, age, light receiving conditions, etc.) in the field, and list the number.
2. The base of the leaf is treated to destroy the phloem of the leaf transport system:
1) For dicotyledons such as cotton, the outer ring of the petiole can be cut about 0.5 cm wide with a blade to cut off the phloem transport.
2) For monocotyledonous plants such as wheat and rice, because the phloem and xylem are difficult to separate, the base of the blade can be burned for a short period of time with a gauze or cotton-wrapped clip that has just been immersed in boiling water (usually boiled for 20 seconds with boiling water above 90 °C) To damage the phloem. It is also possible to burn phloem with paraffin wax at 110~120 °C.
In order to prevent the blade from being treated by hot or ring cutting and not affecting the natural growth angle of the blade, it may be wrapped with tin foil, rubber tube or plastic tube to keep the blade at the original angle of incidence.
3. Cutting the sample: After the base of the blade is processed, the sample can be cut, the time is recorded, and the photosynthetic rate is measured. Generally, half of the symmetrical blades are cut in the order of numbering (the middle vein is not cut), and the blades are placed in the wet gauze in the order of number, and the leaves are placed in the dark. After 4~5 hours (the sample with large light and large leaves can shorten the processing time), and then cut the other half of the leaf, and also the number is clamped in the wet gauze. The order of the two leaf cuts should be as consistent as possible, so that each leaf experiences the same number of hours of illumination.
4. Weighing comparison: stack the two halves of the same number of leaves in the corresponding parts, and put a metal template (or puncher) with a known area (such as cotton available 1.5×2cm) without a thick leaf vein. Cut two leaf pieces along the edge, place them in two weighing dishes labeled as light and dark, and dry them to constant weight (about 5 hours) at 80~90 °C, and weigh them on the analytical balance. Fill in the measurement data according to the table and calculate.
Table Using the modified half-leaf method to determine the photosynthetic rate of plants. Experimenter Date Material Name Illumination Time Leaf Area Vitamins
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