16. Growth parameters-M Sc -E.pptx

Growth parameters in plants

1. Growth parameters

2. GROWTH Growth is defined as an irreversible increase in mass, weight or volume of a living organism, organ or cell.

3. GROWTH CURVE A typical growth curve can be divided into three phases: Lag phase Log phase Stationery phase

4. Lag period of growth: The growth rate is quite slow because it is the initial stage of growth. Log period of Growth : The growth rate is maximum and reaches the top because at this stage the cell division and physiological processes are quite fast . Senescence period (steady state period) The growth is almost complete and become static. Thus the growth rate becomes zero.

5. Measurement of growth Growth can be measured by a variety of parameters as follows: Fresh weight Determination of fresh weight is an easy and convenient method of measuring growth.For measuring fresh weight,the entire plant is harvested,cleaned and then weighed. Dry weight The measurement of dryweight may give a more valid estimation of growth than fresh weight.The dry weight of a plant organ is obtained by drying the material for 21 to 48hrs at 70 to 80°C and weighing it.

6. Length Measurement of length is a suitable indication of growth for those organs which grow in one direction such as roots and shoots.The advantage of measuring length is that it can be done over the same organ over a period of time without destroying the organ. Area It is used to measure the growth of organs like leaf.The area can be measured using graph paper or by electronic leaf area meter which reads leaf area directly as individual leaves are fed into it.

7. GROWTH ANALYSIS It is the process of analyzing the plant growth rate by expressing it as algebraic product of a series of factors. The plant parameters, which are commonly measured to calculate growth rates,are dry matter and leaf area.

8. Crop growth rate It is defined as the dry matter accumulation rate per unit land area per unit time. The CGR is calculated by the following formula W 2 - W 1 CGR = ---------------- (g m -2 d -1 ) A (T 2 - T 1 ) Where CGR is the crop growth rate, W 1 and W 2 are the dry weights at two sampling times T 1 and T 2 respectively. A is the area occupied by the plants

9. Relative growth rate It is defined as the rate of increase in dry matter per unit of dry matter already present. This is also referred as Efficiency index . It provides a valuable overall index of plant growth. The mean relative growth rate over a time interval is given below. Log e W 2 - Log e W 1 RGR = --------------------------- (g g -1 d -1 ) T 2 - T 1 RGR = NAR X LAR

10. Net assimilation rate It is the dry matter accumulation per unit of leaf area. The NAR is a measure of the amount of photosynthetic product going into plant material i.e. it is the estimate of net photosynthetic carbon assimilated by photosynthesis minus the carbon lost by respiration. It is expressed as (g cm -2 wk -1 ) NAR=1/A × dw / dt

11. Leaf Area Ratio The LAR is a measure of the proportion of the plant which is engaged in photosynthetic process. It is defined as the ratio between leaf area in square centimeters and total plant dry weight. It represents leafiness character of crop plants on area basis. A LAR= ---(cm 2 g -1 ) W

12. Specific Leaf Area It is another component of LAR and defined as the ratio between leaf area in cm 2 and total leaf dry weight in grams. This is used as a measure of leaf density. The mean SLA can be calculated as A SLA = -------- (cm 2 g -1 ) WL

13. Specific Leaf Weight The reversal of SLA is called as SLW. It is defined as the ratio between total leaf dry weight in gms and leaf area in cm 2 . It indicates the relative thickness of the leaf of different genotypes. WL SLW = ------- (g cm -2 ) A

14. Leaf area index It is defined as the functional leaf area over unit land area. It represents the leafiness in relation to land area. At an instant time (T) the LAI can be calculated as LAI = A/P (unit less) For maximum production of dry matter of most crops, LAI of 4-6 is usually necessary

15. Leaf Area Duration It is usually expressed as a measure of leaf area integrated over a time period. Some takes into account both the magnitude of leaf area and its persistence in time. It represents the leafiness of the crop growing period. Thus the unit of measurement of LAD may be in days or weeks or months. This is expressed as cm 2 d -1

16. Absolute growth rate It is the function of amount of growth material present and is influenced by environment. It gives absolute value of biomass between two time intervals. It is mainly used for a single plant or single plant organ etc. AGR = H 2 -H 1 / T 2- T 1 Where H1 and H2 are plant heights at times T1 and T2