🌿 Growth Analysis

Growth analysis quantifies crop performance by linking biomass accumulation with leaf area and time. These indices help compare genotypes, treatments, and environments using objective physiological metrics.

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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. 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)

i. Leaf Area

This is the area of photosynthetic surface produced by the individual plant over a

period of interval of time and expressed in cm [2] plant [-1] .

ii. 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.

Total leaf area of a plant

LAI =

Ground area occupied by the plant

iii. 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.

Leaf area per plant

LAR =

Plant dry weight

iv. 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]

Leaf dry weight

LWR =

Plant dry weight

v. 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.

L1 + L2

LAD = X [(t] 2 [ – t] 1 [) ]

L1 = LAI at the first stage

L2 = LAI at the second stage, (t 2 - t 1) = Time interval in days

vi. Specific Leaf Area (SLA)

Specific leaf area is a measure of the leaf area of the plant to leaf dry weight and

expressed in cm [2] g [-1] as proposed by Kvet et al. (1971).

Leaf area

SLA =

Leaf weight

Hence, if the SLA is high, the photosynthesizing surface will be high. However no

relationship with yield could be expected.

vii. 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.

Leaf weight

SLW =

Leaf area

viii. 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.

h2 – h1

AGR = cm day [-1]

t2 – t1

Where, h1 and h2 are the plant height at t1 and t2 times respectively.

ix. 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.

(W2 –W1) (loge L2 - loge L1)

NAR = x

(t2 – t1) (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] )

x. 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] )

loge W2 – loge W1

RGR =

t2 – t1

Where, W1 and W2 are whole plant dry weight at t1 and t2 respectively

t1 and t2 are time interval in days

xi. 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] )

(W2 –W1)

CGR =

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

xii. 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.

xiii. 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.

Straw weight at flowering – straw weight at harvest

TP =

Panicle weight at flowering – panicle weight at harvest

xiv. Light extinction coefficient

It is the ratio of light intercepted by crop between the top and bottom of crop canopy

to the LAI.

loge I / Io

K=

[ LAI ]

Where, Io and I are the light intensity at top and bottom of a population with LAI

xv. 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

xvi. 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.

Grain yield 100

DME = x

TDMP Duration of crop

xvii. Unit area efficiency (UAE)

It is expressed as the quantum of grain yield produced over a unit land area for a

specified crop growth period.

Grain yield 1

UAE = x

Land area Duration of crop

xviii) 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).

Economic yield

HI = x 100

Total biological yield

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Summary Cheat Sheet

Key Indices

• LAI: leaf area per unit ground area.
• CGR: dry matter increase per unit land area per day.
• RGR: biomass increase per unit existing biomass per day.
• NAR: dry matter gain per unit leaf area per day.

Exam Traps

• LAI is not leaf number; it is leaf area/ground area.
• RGR and AGR are different: RGR is relative, AGR is absolute.
• Harvest Index uses economic yield/biological yield, not total dry matter alone.

References

1 source • [1]

[1]

Plant Physiology course notes - Growth Analysis

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