Growth analysis is a mathematical expression of environmental effects on growth and development of crop plants. This is a useful tool in studying the complex interactions between the plant growth and the environment. Growth analysis in crop plants was first studied by british scientists (Blackman, 1919; Briggs, Kidd and West, 1920; William; 1964; Watson; 1952; Blackman, 1968). This analysis depends mainly on primary values (dry weights) and they can be easily obtained without great demand on modern laboratory equipment.
The basic principle that underlie in growth analysis depends on two values
(1) total dry weight of whole plant material per unit area of ground (w) and
(2) the total leaf area of the plant per unit area of ground (a)
The total dry weight (w) is usually measured as the dry weight of various plant parts viz., leaves, stems and reproductive structures. The measure of leaf area (a) includes the area of other organs viz., stem petioles, flower bracts, awns and pods that contain chlorophyll and contribute substantially to the overall photosynthesis of the plants.
According to the purpose of the data, leaf area and dry weights of component plant parts have to be collected at weekly, fortnightly or monthly intervals. These data are to be used to calculate various indices and characteristics that describe the growth of plants and of their parts grown in different environments and the relationship between assimilatory apparatus and dry matter production. These indices and characteristics are together called as growth parameters. Some of the parameters that are usually calculated in growth analysis are crop growth rate (CGR), relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR), leaf weight ratio (LWR), Specific leaf area (SLA), leaf area index (LAI) and leaf area duration (LAD). Accuracy in calculations of these parameters and their correct interpretation are essential aspect in growth analysis.
Advantages of growth analysis :
A) We can study the growth of the population or plant community in a precise way with the availability of raw data on different growth parameters.
B) These studies involve an assessment of the primary production of vegetation in the field i.e. at the ecosystem level (at crop level) of organization.
C) The primary production plays an important role in the energetics of the whole ecosystem.
D) The studies also provide precise information on the nature of the plant and environment
interaction in a particular habitat.
E) It provides accurate measurements of whole plant growth performance in an integrated
manner at different intervals of time.
Drawbacks of growth analysis
In classical growth analysis sampling for primary values consist of harvesting (destructively) representative sets of plants or plots and it is impossible to follow the same plants or plots through out whole experiment.
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