Parameters of primary productivity
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This document discusses parameters used to analyze plant growth, including leaf area index (LAI), leaf area ratio (LAR), leaf area duration (LAD), specific leaf area (SLA), specific leaf weight (SLW), net assimilation rate (NAR), relative growth rate (RGR), crop growth rate (CGR), harvest index (HI), and others. It provides the definitions and equations for calculating each parameter, and cites the scientists who originally proposed the terms. The parameters are used to describe and quantify plant growth, biomass accumulation, and partitioning of assimilates.
Parameters of primary productivity
- 1. Parameters of Primary Productivity Plant Growth Parameters
- 2. Growth Analysis Growth analysis can be used to account for growth in terms that have functional or structural significance. The type of growth analysis requires measurement of plant biomass and assimilatory area (leaf area) and methods of computing certain parameters that describe growth.
- 3. Parameters The growth parameters that are commonly used in agricultural research and the name of the scientists who proposed the parameters are given below. LAI - Williams (1946) LAR - Radford (1967) LAD - Power et al. (1967) SLA - Kvet et al. (1971) SLW - Pearce et al. (1968) NAR - Williams (1946) CGR - Watson (1956) RGR - Williams (1946) HI - Nichiporovich (1951)
- 4. Parameters Leaf Area This is the area of photosynthetic surface produced by the individual plant over a period of interval of time and expressed in cm2 plant-1. The importance of leaf area in relation to basic plant metabolic processes, such as photosynthesis and respiration, is generally recognized. Furthermore, the quantification of several growth analysis parameters requires the measurement of leaf area at several stages during the life cycle of the plant.
- 5. Parameters Leaf area index (LAI): Williams (1946) proposed the term, Leaf Area Index (LAI). It is the ratio of the leaf of the crop to the ground area over a period of interval of time. The value of LAI should be optimum at the maximum ground cover area at which crop canopy receives maximum solar radiation and hence, the TDMA will be high. LAI = Total leaf area of a plant / Ground area occupied by the plant.
- 6. Parameters Leaf Area Ratio (LAR): The term, Leaf Area Ratio (LAR) was suggested by Radford (1967), expresses the ratio between the area of leaf lamina to the total plant biomass or the LAR reflects the leafiness of a plant or amount of leaf area formed per unit of biomass and expressed in cm-2 g-1 of plant dry weight. LAR = Leaf area per plant / Plant dry weight
- 7. Parameters Leaf Weight Ratio (LWR): It was coined by (Kvet et al., 1971) Leaf weight ratio is expressed as the dry weight of leaves to whole plant dry weight and is expressed in g g –1 . LWR = Leaf dry weight / Plant dry weight
- 8. Parameters Leaf Area Duration (LAD) To correlate dry matter yield with LAI, Power et al. (1967) integrated the LAI with time and called as Leaf Area Duration. LAD takes into account, both the duration and extent of photosynthetic tissue of the crop canopy. The LAD is expressed in days. LAD = (L1 + L2 / 2 ) × (t2 – t1) L1 = LAI at the first stage L2 = LAI at the second stage (t 2 - t 1) = Time interval in days
- 9. Parameters Specific Leaf Area (SLA): Specific leaf area is a measure of the leaf area of the plant to leaf dry weight and expressed in cm2 g-1 as proposed by Kvet et al. (1971). SLA = Leaf area / Leaf weight Hence, if the SLA is high, the photosynthesizing surface will be high. However no relationship with yield could be expected.
- 10. Parameters Specific Leaf Weight (SLW): It is a measure of leaf weight per unit leaf area. Hence, it is a ratio expressed as g cm- 2 and the term was suggested by Pearce et al. (1968). More SLW/unit leaf area indicates more biomass and a positive relationship with yield can be expected. SLW = Leaf weight / Leaf area
- 11. Parameters Absolute Growth Rate (AGR): AGR is the function of amount of growing material present and is influenced by the environment. It gives Absolute values of biomass between two intervals. It is mainly used for a single plant or single plant organ e.g. Leaf growth, plant weight etc. AGR = ( h2 – h1 / t2 – t1) cm day-1 Where, h1 and h2 are the plant height at t1 and t2 times respectively.
- 12. Parameters Net Assimilation Rate (NAR): The term, NAR was used by Williams (1946). NAR is defined as dry matter increment per unit leaf area or per unit leaf dry weight per unit of time. The NAR is a measure of the average photosynthetic efficiency of leaves in a crop community. NAR = (W2-W1) / (t2 – t1) × (loge L2 - loge L1) / (L2 - L1) Where, W1and W2 is dry weight of whole plant at time t1 and t2 respectively L1 and L2 are leaf weights or leaf area at t1 and t2 respectively t1 – t2 are time interval in days NAR is expressed as the grams of dry weight increase per unit dry weight or area per unit time (g g -1 day-1 ).
- 13. Parameters Relative Growth Rate (RGR): The term was coined by Williams (1946). Relative Growth Rate (RGR) expresses the total plant dry weight increase in a time interval in relation to the initial weight or Dry matter increment per unit biomass per unit time or grams of dry weight increase per gram of dry weight and expressed as unit dry weight / unit dry weight / unit time (g g -1 day-1 ). RGR = loge W2 – loge W1 / t2 – t1 Where, W1 and W2 are whole plant dry weight at t1 and t2 respectively t1 and t2 are time interval in days
- 14. Parameters Crop Growth Rate (CGR): The method was suggested by Watson (1956). The CGR explains the dry matter accumulated per unit land area per unit time (g m-2 day-1 ). CGR = (W2 –W1) / ρ (t2 – t1) Where, W1 and W2 are whole plant dry weight at time t1 – t2 respectively ρ is the ground area on which W1 and W2 are recorded. CGR of a species are usually closely related to interception of solar radiation.
- 15. Parameters Total dry matter production (TDMP) and its distribution: The TDMP is the biomass accumulated by the whole plant over a period of interval of time and its distribution (allocation) to different parts of the plant such as roots, stems, leaves and the economic parts which controls the sink potential.
- 16. Parameters Translocation percentage (TP): The term translocation percentage indicates the quantum of photosynthates translocated from source (straw) to the grain (panicle/grains) from flowering to harvest. TP = Straw weight at flowering – straw weight at harvest / Panicle weight at flowering – panicle weight at harvest
- 17. Parameters Light extinction coefficient: It is the ratio of light intercepted by crop between the top and bottom of crop canopy to the LAI. K= (loge I / Io) / LAI Where, Io and I are the light intensity at top and bottom of a population with LAI.
- 18. Parameters Light Transmission Ratio (LTR): It is expressed as the ratio of quantum of light intercepted by crop canopy at top to the bottom. Light intensity is expressed in K lux or W m-2. LTR = I / Io Where, I : light intercepted at the bottom of the crop canopy Io: light intercepted at the top of the crop canopy
- 19. Parameters Dry Matter Efficiency (DME): It is defined as the percent of dry matter accumulated in the grain from the total dry matter produced over the crop growth period. DME = (Grain yield / TDMP ) × ( 100 / Duration of crop )
- 20. Parameters Harvest Index: The harvest index is expressed as the percent ratio between the economic yield and total biological yield and was suggested by Nichiporovich (1951). HI = Economic yield / Total biological yield × 100
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