Parameters arrived through growth analysis

Parameters arrived through growth analysis

    1) Leaf Area (LA)
    • It is the surface area of leaf, which aids in photosynthesis.
    • Total leaf area per plant is often a useful measurement in bio-productivity studies.
    • Area can be measured by graphic methods, weight method, by using Leaf Area Meter and by measuring length and breadth of the leaf.
    A) Weight method
    LA = ---------- x B
    X = known area of leaves
    A = dry weight of known area of leaf
    B = dry weight of unknown area of all leaves
    The leaf area of standard leaves, usually 3rd leaf from the top is measured and dried.

    B) Linear measurement method
    LA = LBK (cm2 or m2)
    L=maximum length, B=maximum breadth, K=constant (can be worked out by regression analysis)
    K value may not be the same for different varieties in the same species.
    2) Leaf Area Index (LAI)
    • Watson (1947) proposed the term leaf area index which is the ratio of the leaf area of a plant to the ground area occupied by the plant.

    Total leaf area of the plant
    Leaf area index = -----------------------------------------------------
    Ground area occupied by the plant (spacing)

    3) Leaf Area Ratio (LAR)
    • The term leaf area ratio was suggested by Redford (1967).
    • It is defined as the ratio of area of the leaf to the total plant biomass per plant.
    • It is expressed in terms of cm2g-1.
    Leaf area per plant
    LAR = -----------------------------
    Total plant dry weight

    4) Leaf Area Duration (LAD)

    • It is ability of the plant to maintain the green leaves per unit area of the land over a period of time.
    • It reflects the vitality of leaves and an opportunity for assimilation.
    • It also measures the persistence of the assimilating surface.
    • This factor was suggested by Power et al.(1967) and expressed in days.

    L1 + L2
    LAD = ----------------- x (t2 – t1)
    LAI (i) – Leaf area index at first stage
    LAI (ii) - Leaf area index at second stage
    t2 –t1 – Time interval between the two consequent stages and expressed in days.

    5) Leaf Area Ratio (LAR)
    • In order to estimate the carbon assimilatory efficiency of leaves or to estimate the leafiness of plants, Radfort (1967) suggested leaf area ratio as a measure of leaf area to the weight of the whole plant. It is expressed as cm2 g-1.

    L1 + L2
    LAD = ----------------- x (t2 – t1)
    • In broad sense, LAR represents the ratio of photosynthesizing to respiratory material within the plant.
    6) Specific Leaf Area (SLA)
    • It is the ratio of assimilating area to its dry weight.
    • Following formula was proposed by Kvet et al. (1971) to arrive SLA and expressed as cm2 g-1.

    Leaf area
    SLA = --------------------------
    Leaf dry weight

    7) Specific Leaf Weight (SLW)

    • Using the leaf dry weight and leaf area, SLW is calculated.
    • It is the ratio of leaf dry weight to its area of assimilating surface.
    • The formula was suggested by Pearce et al. (1968) and expressed as mg cm-2.

    Leaf weight
    SLW = -----------------
    Leaf area

    8) Leaf Weight Ratio (LWR)
    • It is the ratio of total leaf dry weight to the whole plant dry weight.
    • It is the measure of leafiness of the plant on a weight basis.
    • It is expressed in g kg-1.
    Leaf dry weight
    LWR = ----------------------------------------
    Total plant dry weight

    9) Net Assimilation Rate (NAR)
    • It is the rate of increase of leaf by dry weight per unit area of leaf per unit time.
    • Williams (1946) employed the formula and expressed as mg cm-2 day -1



    Log e L2 = Natural log of leaf area at stage 2.
    Log e L1 = Natural log of leaf area at stage 1.
    L2 & L1 = Leaf area at stage 2 & 1 respectively
    W2 & W1 = Dry weight of the whole plant at stage 2 & 1 respectively
    t2-t1 = Time interval between the two stages
    NAR is expressed as mg cm-2 day -1

    10) Relative Growth Rate (RGR)
    • It is the rate of increase of dry weight per unit weight already present per unit time.
    • Williams (1946) suggested the formula.

    Loge W2 – loge W1
    RGR = -----------------------
    t2 – t1
    W2 & W1 = Whole plant dry weight at t2 & t1 respectively and expressed as g g-1 day-1
    11) Crop Growth Rate (CGR)
    • CGR is a simple and important aid of agriculture productivity.
    • It is the rate of increase of dry weight per unit land area per unit time.
    • Watson (1958) suggested the following formula to arrive Crop Growth Rate

    W2 and W1 are total plant dry weight at time t2 and t1 and P is plant population per unit area.
    CGR is also the product of leaf area index and net assimilation rate.
    CGR increases as LAI increases to an optimum because of greater light interception.
    CGR is expressed as mg m-2 day -1.

    12) Harvest Index (HI)
    • It reflects the proportion of assimilate distribution between economic yield and total biomass yield (Donald and Hamblin, 1976).

Last modified: Wednesday, 13 June 2012, 6:34 AM