Measurements in plant growth

We can measure the growth of an organism by measuring its mass, length, height, width and area or volume. Over a period of time, sometimes it's possible to measure just one of an organism such as, the leaf of a plant, but this part must grow in proportion to the complete organism. In the case of seedlings, the number of leaves may be used as a growth indicator. Each of these growth indicators is known as a parameter of growth.
The pattern of growth of an organism would vary with the growth parameter that is used. In growth studies, the parameter used would depend on the type of organism. For example, we can measure the height of maize plant to estimate it's growth, but we cannot use the same parameter to assess the growth of a mouse. The ease of measuring a growth parameter will also determine its usage. Thus, area and volume measurements give an accurate picture of growth but are often difficult to measure and so are rarely used.
Mass and length are the most commonly used growth parameters since they are easy to measure. However, the results obtained may not be very accurate or reliable. For example, a seedlings grown in the dark increases in height more rapidly than a similar seedling in the sunlight but it is the seedling in the sunlight that shows greater growth in terms of an increase in protoplasmic material. Using measurements of mass may also be misleading. If an organism takes in large amount of water its mass may increase temporarily. This, however cannot be considered as growth. In most growth studies mass may be measured as wet mass or dry mass. Wet mass is the mass of the organism under normal conditions. It is not a reliable indication of growth.
Dry mass, is the mass of an organism after all the water in it has been removed. Although measuring growth in terms of dry mass is an accurate and reliable method, the organism get killed in the process. This means that it is not possible to measure growth in the same organism. To study growth by measuring dry mass, we must carry out the study on a large number of similar organisms.

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