Experiments for the determination of photosynthetic intensity
Experiments for the determination of photosynthetic intensity
Modified half-leaf method is part of the plant symmetrical leaf shade or remove placed in the dark, the other part is left in the light for photosynthesis, after a certain period of time, in these two parts of the corresponding part of the leaf to take the same area, respectively, drying and weighing, because of symmetry of the two corresponding parts of the leaf dry weight of the same area of the original equal, the weight of the leaf after the light exceeds the weight of the leaf in the dark, more than part of the weight of the products of photosynthesis, and through certain calculations can be obtained. And through certain calculations can be obtained photosynthesis intensity.
Operation method
Experiments for the determination of photosynthetic intensity
Principle
Modified half-leaf method is part of the plant symmetrical leaf shade or remove placed in the dark, the other part is left in the light for photosynthesis, after a certain period of time, in these two parts of the corresponding part of the leaf to take the same area, respectively, drying and weighing, because of symmetry of the two corresponding parts of the leaf dry weight of the same area of the original equal, the weight of the leaf after the light exceeds the weight of the leaf in the dark, more than part of the weight of the products of photosynthesis, and through certain calculations can be obtained. And through certain calculations can be obtained photosynthesis intensity. Move II. Instrumental drugs For more product details, please visit Aladdin Scientific website.
Scissors Analyzing balance
Weighing Dish Oven
Razor blades Metal templates
Gauze Tinfoil
Trichloroacetic acid
Experimental steps
1. Selection of samples
Select 20 representative plant leaves (e.g., leaf part on the plant, leaf age, light condition, etc.) in the field, and number them with small paper plates.
2. Leaf base treatment
In order not to make the photosynthesis products in the selected leaves transported outward and affect the accuracy of the determination can be treated in the following way.
(1) The phloem of the leaf transport system can be destroyed. Such as cotton and other dicotyledonous plant leaves can be used to blade the petiole of the phloem ring cut about 0.5 cm wide.
(2) Such as wheat, rice and other monocotyledonous plants, due to the phloem and xylem are difficult to deal with separately, can be used just soaked in boiling water gauze or cotton made into a clip at the base of the leaf can be scalded in a small section (generally more than 90 ° C boiling water for 20 seconds).
(3) due to the cotton petiole lignification degree is low, the petiole is easy to break. Scalded with boiling water and difficult to grasp the degree of scalding, often either not enough scalding is too heavy to make the leaf drooping, changing the angle of the leaf. Therefore, chemical treatment can be used instead, using the appropriate concentration of trichloroacetic acid spot coating petioles to prevent the output of photosynthesis products. TCA is a strong protein precipitant, and after penetrating into the petiole, it can kill the living cells of sieve tubes and prevent the transportation of organic substances. The concentration of TCA varies depending on the degree of tenderness of the petiole, and it is preferable to be able to significantly burn the petiole without affecting water supply or changing the angle of the leaf blade. Generally 5% TCA is used. In order to make after scalding or ring cutting and other treatment of the leaf does not sag to affect the natural growth angle of the leaf blade can be used tinfoil or plastic tube surrounded by, so that the leaf blade to maintain the original growth angle.
3. Cutting samples
After the leaf base treatment, you can cut the sample, record the time, start photosynthesis measurement. Generally according to the number order were cut off half of the symmetrical leaves (the main veins are not cut off), according to the number order of the clip in a moist gauze, stored in the dark. After four or five hours, and then cut the other half of the leaves in turn, also according to the number of the clip in the moist gauze, the speed of the two cut leaves should try to maintain consistency, so that the leaves experience equal light time.
4. Weighing Comparison
Will be the same number of leaf halves according to the corresponding parts of the iteration together, in the absence of thick veins with a known area of the perforator to take a number of small round leaves were placed in the light and the dark in the two weighing dishes, baked to a constant weight at 80-90 ℃ (about 5 hours), in the analytical balance on the weighing comparisons.
5. Calculate the results
The sum of the difference in dry weight of leaves (expressed in mg) was divided by the area of leaves (converted to dm2, 1dm2=100cm2) and the number of hours of light, i.e., the intensity of photosynthesis was obtained, which was expressed as mg/dm2-h of dry matter. The formula is as follows: 
Since the photosynthetic products stored in the leaves are generally sucrose and starch, etc., the weight of the dry matter can be multiplied by a factor of 1.5 to obtain the amount of carbon dioxide assimilation in units of CO2mg/dm2-h.