Transpiration is an important process of water metabolism in plants. The speed of transpiration is related to the rate of upward transport of mineral salts and other salts in the plant, as well as leaf temperature, etc. In particular, the rate of transpiration can also be used as an important indicator for determining the degree of water demand. The rapid weighing method is characterized by the fact that it can be carried out under natural conditions. Although the plant branches are cut away from the mother body, there is no obvious change in physiology within a short period of time, so the obtained transpiration rate is similar to the actual situation. However, this method cannot continuously measure and automatically record the transpiration rate over a long period of time, which is a disadvantage of this method. The purpose of this experiment is to master the principle and method of determining the transpiration rate of plants by the rapid weighing method in vitro.
Operation method
Plant transpiration rate measurement experiment
Principle
Plants lose water by transpiration and lose weight, so the rate of transpiration can be found by measuring the amount of water lost from a certain leaf area in a certain period of time by weighing the plant leaves.
Materials and Instruments
Plant leaves with branches Move 1. Transpiration measurements Caveat Calculation of transpiration rateTranspiration water volume (mg) × 60Transpiration rate (mgH20-dm-2-h-1) = ---------------- Leaf area (dm)2) × measurement time (min)Record Sheet for Transpiration Rate Determination by Rapid In Vivo Weighing Method Common Problems 1. If it is a conifer and other plants are inconvenient to calculate the leaf area, you can transpiration per unit weight (fresh or dry weight) transpiration organization, the amount of water transpired in a unit of time to indicate the rate of transpiration (mgH2O-g-1-h-1). For more product details, please visit Aladdin Scientific website.
Electronic analytical balance Scissors White paper sheet
Normal-growing leafy branches weighing about 5 to 100 g and with a leaf area of 1 to 3 dm2 were selected from the plant under test, then cut and immediately weighed for the first time, and the start time and weight of the material under test were recorded, then the isolated leafy branches were quickly put back to the parent plant from which the sample was taken, so that they could transistilate for 3 to 5 min under the original ambient conditions, then a second weighing was quickly performed and the water loss within 3 to 5 min of transpiration water loss and record the experimental data.
2. Leaf area measurement (if available, use leaf area meter to measure)
Leaf area was determined by the method of weighing paper cuttings as follows:
(1) take the same thickness of white paper, cut into (10cm × 10cm = 1dm2) area of the paper, weighing (mg).
(2) Lay the measured leaf on the same piece of white paper, trace the leaf shape of the measured leaf with a pencil (without petiole and branches), and then cut the paper leaf and weigh it (mg).
(3) Calculate the leaf area of the tested leaf according to the following formula
Weight of paper leaf (mg)
Leaf area ( dm2 ) = ---------
1dm2 Paper blade weight (mg)
2. The above measurements can be repeated appropriately to find the average value. Compare different time (morning, afternoon, evening). Different environments (temperature, humidity, wind, light), different plants or different parts of the transpiration rate, the results and the prevailing climatic conditions recorded in the table, and explained.