Leaf Surface Area: How to Measure Crop Performance and Why?

Researchers who work with plants performance repeatedly face difficulties to measure leaf surface area. But why this plant data is important and how to measure this important plant characteristic?
by Maryna Kuzmenko | 29th January 2016 | 9 min read
cover photo

Introduction

Researchers who work with plants performance repeatedly face difficulties to measure leaf surface area. The most difficult task for most of the crop scientists is to define leaf area of complex leaves. The hidden problem of this challenge is related to the curved contour of these leaves.

Hence, the question is about why do we need to struggle so much and measure leaf surface area? What value does leaf area bring about the plant growth?

What Is The Problem With Leaf Surface Area Measurement?

Leaf is a mirror of the plant’s health and leaf area is one of the key parameters of tracking the plant’s growth. As a result, the more data is available to get about the leaf – the better quality of decision making is expected.

On one hand, the problem of leaf area measurement is not a problem at all. There are plenty of methods how to measure this key performance indicator for plants in ecophysiological studies.

On the other hand, the most popular methods are not effective but time consuming, not accurate or not convenient.

For example, millimetre graph paper method is widely used for leaf area estimation. Based on this method, the leaf area is estimated by tracing the shape of every leaf on a graph paper. It is accurate but laborious when there are large numbers of leaves for area estimation [1].

Weight paper method is one of the widely used as well and has significant linear relationships with the estimates obtained by using sophisticated leaf area meter [2].

The leaf dimension method of determining leaf area requires only a millimeter rule, but it is also time-consuming [3].

In these circumstances, to illustrate the correctness of measurements and to reduce the value of the error, it is necessary to increase the number of repetitions of measurements, which in turn requires extra time.

That’s why in accordance with fast pace of plant phenotyping there is a need to find a method of effective and accurate leaf area measurement to leverage the cutting edge technologies for plant science.

Indirect and direct methods for leaf surface area measurement

Indirect leaf area measurement includes non-destructive methods but direct leaf area measurement can be divided on destructive and non-destructive as well. Direct methods are simple to perform and accurate, but they require time and efforts. Additionally, some of them become unviable for endangered species. Also there are issues to use this methods on plants smaller in size, and for plants at their growth stage, when it is not possible to cut out leaves due to possible severe damage to the plant.

In contrast, indirect methods are quicker in their performance. They are also precise for plants growing in different environmental conditions, and allow multiple evaluations of the same individual plant without destroying the sample [4].

How to find the leaf surface area of a leaf?

Leaf surface area can be estimated through different methods:

  1. Using visual and manual approach, for example, graph paper methods, weight paper method.
  2. By leverage of equipment - ruler, mechanical planimeter or photo-planimeter, handheld leaf area scanner or office scanner.
  3. With PC software, for example, ImageJ, WinFolia, Adobe Photoshop).
  4. With smartphone mobile application such as Petiole Pro, Petiole App, Easy Leaf Area, etc.

Does the leaf surface area and specific leaf mean the same?

No, it is not the same. It is not correct to use definition of leaf surface area as specific leaf area and vice versa. Some crop researchers incorrectly use “specific leaf area” with the same meaning as “leaf surface area” to determine how much new leaf area to deploy for each unit of biomass produced. However, the definition of these terms are different. Leaf surface area is an area of a leaf surface. At the same time, specific leaf area is the ratio of leaf area to leaf weight [3] and it explains more complex relationship between plant traits [5, 6, 7]

Is the leaf surface area and leaf area index the same?

Not exactly. The LAI of a plant is widely used for assessment of canopy. It is defined as leaf area of all leaves in canopy per unit of ground area. however, leaf surface area

Does leaf surface area and leaf size mean the same?

No, leaf surface area is just one of the components of leaf size. In fact, leaf size includes different leaf parameters, for example, leaf surface area, leaf dry mass and leaf length. [8].

What is leaf area, leaf surface area and leaf area index?

Leaf area and Leaf surface area in most cases mean the same. However, they differ from leaf area index. All three terms (words) are associated with the photosynthetic capacity of plants, but the meaning of “leaf area index” is wider. It means the proportion of leaf area per unit of land area and to get leaf area index you must know the leaf area. The basic LAI formula is LAI = [Leaf area (m2)/Ground cover (m2)], but there are more complicated versions. For example, the formula to calculate leaf area index based on leaf surface area and weight is: —image— This Leaf Area Index formula includes the following numbers:

  • Dry weight sampling area in grams;
  • Sampling area, which is leaf area or leaf surface area in square centimetres;
  • Leaf dry weight in grams;
  • Leaf area in square centimetres [9].

Why Is Leaf Surface Area Important?

Determination of leaf surface area brings value for agronomists, plant breeders, biologists and ecologists.

Leaf area in Agronomy

Knowledge of leaf apparatus is necessary for numerous calculations in agronomy. It is critical for an understanding of crop production as a result of its relevance to light interception, crop growth, weed control, crop–weed competition, crop water use, and soil erosion.

The most important of the tasks why does agronomist need to measure leaf area are linked to the determination of:

  • Transpiration of crops for setting irrigation standards;
  • Photosynthetic pigments in cells of crop leaves;
  • Area of leaves impacted by plant diseases and pests;
  • Calculation of economic damage threshold force;
  • Performance of vegetative mass of plants.

Leaf Surface Area Measurement for Plant Breeders

In the breeding work Leaf Surface Area is used to determine the impact of varietal characteristics on two aspects of crop development:

  • Forming leaf apparatus
  • Resistance to diseases and pests lesions

Role of Leaf Surface Area in Ecology

Simultaneously, in ecology leaf area measurement will are helpful for:

  • Assessment of photosynthetic capacity of plants;
  • Determining the impact of environmental conditions on the formation of plants
  • Defining the populations of insects and microorganisms that affects plants

Case Study of Leaf Surface Area Measurement

Below you can find the case studies that are a powerful tool to increase your understanding why to measure leaf surface area is important. Using these in-depth case study highlights it is easier to gasp how leaf surface area measurement can bring value for your plant science research.

Leaf Surface Area of Maize after Application of Bio-based products

Two Ukrainian scientists from the National University of Life and Environmental Sciences together with their colleagues from the Institute of Energy Crops and Sugar Beet conducted an experiment on maize with application of pre-sowing treatment.

After application of bio-based products Mycofriend, Mikovital and Florobacillin (all produced in Ukraine) scientists measure performance indicators for maize. Leaf surface area was measured for 30th, 60th, 90th and 120th days of vegetation. It was measured alongside other parameters such as water content and mass of leaves and root system, soil moisture holding capacity and its physical state and yield. Researchers have randomly selected 100 leaves in each variant (25 leaves from each repetition).

The results of this experiment were published in April 2021 as a part of E3S Web of Conferences.

Non-destructive leaf area measurement of alfalfa in biotechnology

A group of Canadian breeders works on improvement of drought tolerance mechanisms in a forage crops. Particularly, alfalfa, as one of the most important crops for feeding animals, is in their focus.

They carried experiments with alfalfa and measured leaf surface area destructively for 45 leaves but non-destructively for 16 leaves.

The results of their research are published in Frontiers in Plant Science on January 13, 2022.

Leaf Surface Area and Leaf Area Ratio in Beech Forest Research

Researchers from Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), were researching the survival time and mortality rate of regeneration in the deep shade of a primeval beech forest.

They suggested that Leaf Area Ratio (LAR), as an alternative to radial stem growth, can be one of the key characteristics of beech forests. In particular, for explaining mortality in juvenile trees.

The scientists measured leaf surface area of 289 living seedlings and saplings to use these measurements for Leaf Area Ratio (LAR) calculation. They used the formula: LAR = LA/m(total), where LA denotes leaf area and m(total) is the total dry mass (aboveground and belowground) of the tree.

The scientific paper about this research was published in European Journal of Forest Research on 5 November 2021.

Conclusions

Leaf surface area is one of the widely used performance indicator for plants. It helps to get better understanding the adaption strategy of plants to environmental changes and track plant development. Leaf surface area is a crucial parameter for agronomy, plant breeding and ecology. There are a variety of methods for leaf surface measurement but the choice of specific way how to calculate leaf area depends on the plants under research.

References

[1] Jadon M. A Novel Method for Leaf Area Estimation based on Hough Transform. Journal of Multimedia Processing and Technologies, Volume 9, No. 2, June 2018, https://doi.org/10.6025/jmpt/2018/9/2/33-44

[2] Pandey S., Singh H. A simple cost-effective method for leaf area estimation. Journal of Botany, 2011, https://doi.org/10.1155/2011/658240

[3] Wolf D., Carson E., Brown R. Leaf Area Index and Specific Leaf Area Determinations, 1972, https://www.crops.org/files/publications/nse/pdfs/jnr001/001-01-0024.pdf

[4] Non-destructive method for estimating leaf area of Erythroxylum pauferrense (Erythroxylaceae) from linear dimensions of leaf blades. Acta botánica mexicana, no. 127, e1717, 2020, https://doi.org/10.21829/abm127.2020.1717

[5] Chelli, S., Ottaviani, G., Simonetti, E., Campetella, G., Wellstein, C., Bartha, S., Cervellini, M. and Canullo, R. Intraspecific variability of specific leaf area fosters the persistence of understorey specialists across a light availability gradient. Plant Biol J, 23: 212-216. https://doi.org/10.1111/plb.13199 .

[6] de Ávila Silva, L., Omena-Garcia, R.P., Condori-Apfata, J.A. et al. Specific leaf area is modulated by nitrogen via changes in primary metabolism and parenchymal thickness in pepper. Planta 253, 16 (2021). https://doi.org/10.1007/s00425-020-03519-7

[7] Firn, J., McGree, J.M., Harvey, E. et al. Leaf nutrients, not specific leaf area, are consistent indicators of elevated nutrient inputs. Nat Ecol Evol 3, 400–406 (2019). https://doi.org/10.1038/s41559-018-0790-1

[8] Wang C, He J, Zhao T-H, Cao Y, Wang G, Sun B, Yan X, Guo W and Li M-H (2019) The Smaller the Leaf Is, the Faster the Leaf Water Loses in a Temperate Forest. Front. Plant Sci. 10:58. https://doi.org/10.3389/fpls.2019.00058

[9] Campillo C., García M., Daza C., Prieto M. Study of a Non-destructive Method for Estimating the Leaf Area Index in Vegetable Crops Using Digital Images, HortScience, 45:10. https://journals.ashs.org/hortsci/view/journals/hortsci/45/10/article-p1459.xml?rskey=0ngapT

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