Plant productivity is decreasing due to detrimental effects of various biotic and abiotic yield reduction factors that are majorly environmental in nature. Therefore, minimizing these losses is a major area of concern to ensure food and fiber security under the ever changing climate.

Environmental abiotic stresses, such as drought, extreme temperature, cold, heavy metals, or high salinity, severely impair plant growth and productivity.

In many regions of world, crop losses due to increasing water shortage will further aggravate the impacts of climate change; the most noticeable is the reduction in yields and yield component of plants.

To properly understand yield and yield components of plants, you have to study and know the morphological characteristics of plants.

Plant morphology examines the pattern of development, the process by which structures originate and mature as a plant grows. While animals produce all the body parts they will ever have from early in their life, plants constantly produce new tissues and structures throughout their life.

Plant Morphology and Characteristics

Plant morphology or phyto-morphology is the study of the physical form and external structures of plants. Plant morphology is useful in the visual identification of plants.

It represents a study of the development, form, and structure of plants, and by implication, an attempt to interpret these on the basis of similarity in plants and origin.

When structures in different species are believed to exist and develop as a result of common, inherited genetic pathways, those structures are termed to be homogenous.

For example, the leaves of mango, orange and guava all look very different, but share certain basic structures and arrangement of parts.

Secondly, plant morphology observes both the vegetative (somatic) structures of plants, as well as the reproductive structures. The vegetative structures of vascular plants include the study of the shoot system, composed of stems and leaves as well as the root system.

The reproductive structures are more varied, and are usually specific to a particular group of plants, such as flowers and seeds. At the largest scale is the study of plant growth habit, the overall architecture of a plant.

A plant morphologist examines the pattern of development, the process by which structures originate and mature as the plant grows.

The way in which new structures develop and mature might be affected in the plant’s life when they begin to be influenced by the environment to which the structures are exposed.

A morphologist studies this process, the causes, and its final result on the yield and yield components of the plant.

Yield Components of Plants

Yield Components of Plant Productivity and Limiting Factors

One of the metrics used to determine the efficiency of food production is crop yield. Crop yield (also known as “agricultural output”) refers to both the measure of the yield of a crop per unit area of land and the grain resulting yield usually expressed as ton per hectare.

As plants grow after germination and within the competitive biotic and abiotic environment, structures and components of the plant emerge and grow. These vegetative structures include the stems, leaves, shoot system, the root system. Later in the life of the plant, reproductive organs emerge or develop.

The performance of these structures and organs including the canopy size and form, branches and vines all will sum up into yields or products of choice. Depending on the crop, and the output of interest, yield components of some selected crops will include the followings.

Rice Yield Components

Average leaf length (cm)
Average leaf width (mm)
Average number of leaf per plant
Germination percentage (%)
Total number of tillers/m²
Number of days to heading
Number of days to maturity
Plant height (cm)
Weight of 1000 seed (gm)
Grain yield(t/ha)
Total tillers/ m²
Number of effective tillers/ m²
Panicle length (cm)
Total grain per panicle

Yield Components of Maize

Growth components of maize

Plant height (cm) at 4, 8, 12 WAP
Number of leaves/plant
Length of leaf (cm)
Width of leaf (cm)
Leaf area index

Yield components of maize

Dry cob weight (t/ha)
Number of cobs per plant
Number of seed per cob
Dry grain weight (t/ha)
Dry Stover weight at harvest (t/ha)
weight of 100 seeds (gm)

Yield Components of Bambara Groundnut

Growth components of Bambara groundnut

Number of days to 50% flowering of bambara groundnut
Number of days to maturity of bambara groundnut
Number of leaves per plant of bambara groundnut
Canopy width (cm) of bambara groundnut
Plant height (cm) of bambara groundnut
Length of tap root (cm) at 50% flowering of bambara groundnut
Number of lateral roots at 50% flowering of bambara groundnut

Length of longest lateral root at 50% flowering of bambara groundnut

Yield Components of Bambara groundnut

Number of pods per plant
Number of seeds per pod
100 seed weight(g)
Dry pod weight (t/ha)
Seed yield (t/ha) of bambara groundnut
Shelling percentage (%)
Total plant biomass (t/ha)
Shoot dry matter at harvest (t/ha)
Dry root weight at harvest (t/ha)
Number of nodules per plant
Dry weight of nodules per hectare (kg/ha)

Yield Components of Cowpea

Number of branches/stand
Number of pods/stand
Length of pod (cm)
Number of seeds/pod
100 seed weight (g)
Dry grain weight (t/ha)
Shelling percentage (%)
Harvest index
Dry root weight at harvest (t/ha)
Total plant biomass (t/ha)
Dry pod weight (t/ha)
Shoot dry matter (t/ha)

Yield Components of Sunflower

Plant height (cm)
Stem diameter (cm)
Head diameter (cm)
1000 seed weigh (gm)
Dry matter (t/ha)
Harvest index
Seed yield per plant (gm)
Seed yield (t/ha)
Leaf number
1000 seed weight (gm)

Plant Yield Limiting Factors

Plants require a balance of six critical factors in order to optimize growth – temperature, humidity, carbon dioxide, water, nutrients, and light. When growing in a controlled environment, growers can control these conditions to maximize their plants’ growth potential.

There are limits to a plant’s ability to utilize each parameter at any given time. Overexposure to any one factor can be detrimental to plant health and growth rate.

For example, fertilization allows the plant access to extra resources to increase growth rates but too many nutrients can be toxic, resulting in burned plant roots.

Water is necessary, but if a plant is over-watered, the oxygenation of the root zone is reduced thereby killing the plant. Some of these yield limiting factors are environmentally based and are as summarized below.

Rainfall and Water

Rainfall is the most common form of precipitation. It is the falling of water in droplets on the surface of the Earth from clouds.

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The amount and regularity of rainfall vary with location and climate types and affect the dominance of certain types of vegetation as well as crop growth and yield.

1. Light

Light is a climatic factor that is essential in the production of chlorophyll and in photosynthesis the process by which plants manufacture food in the form of sugar (carbohydrate) and subsequently into other organic compounds.

Three properties of this climatic factor that affect plant growth and development are light quality, light intensity and day length (photoperiod).

Light quality refers to the specific wavelengths of light; light intensity is the degree of brightness that a plant receives; and day length is the duration of the day with respect to the night period.

Aside photosynthesis, other plant processes that are enhanced or inhibited by this climatic factor include stomatal movement, phototropism, photomorphogenesis, translocation, mineral absorption,and abscission.

2. Temperature

The degree of hotness or coldness of a substance is called temperature. It is commonly expressed in degree Celsius or centigrade (C) and degree Fahrenheit (F).

This climatic factor influences all plant growth processes such as photosynthesis, respiration, transpiration, breaking of seed dormancy, seed germination, protein synthesis, and translocation.

At high temperatures the translocation of photosynthate is faster so that plants tend to mature earlier. In general, plants survive within a temperature range of 0 to 50 C. The favourable or optimal day and night temperature range for plant growth and maximum yields varies among crop species.

Enzyme activity and the rate of most chemical reactions generally increase with rise in temperature.

Up to a certain point, there is doubling of enzymatic reaction with every 10 C temperature increase. But at excessively high temperatures, denaturation of enzymes and other proteins occur.

Excessively low temperatures can also cause limiting effects on plant growth and development.

For example, water absorption is inhibited when the soil temperature is low because water is more viscuous at low temperatures and less mobile, and the protoplasm is less permeable.

3. Air

The air is a mixture of gases in the atmosphere. The oxygen and carbon dioxide in the air are of particular importance to the physiology of plants.

Oxygen is essential in respiration for the production of energy that is utilized in various growth and development processes. Carbon dioxide is a raw material in photosynthesis.

4. Relative Humidity

Relative humidity (RH) is the amount of water vapour in the air, expressed as the proportion (in percent) of the maximum amount of water vapor it can hold at certain temperature.

For example, an air having a relative humidity of 60% at 27^o C temperature means that every kilogram of the air contains 60% of the maximum amount of water that it can hold at that temperature.

The relative humidity affects the opening and closing of the stomata which regulates loss of water from the plant through transpiration as well as photosynthesis.

5. Wind as Climatic Factor

Air movement or wind is due to the existence of pressure gradient on a global or local scale caused by differences in heating.

This climatic factor serves as a vector of pollen from one flower to another thus aiding in the process of pollination.

It is therefore essential in the development of fruit and seed from wind-pollinated flowers as in many grasses.

6. Nutrients

There are optimum levels of nutrient availability that should be met in the soil and plant for maximum crop production. Understanding and managing plant nutrients for crop production is of paramount importance.

7. Soil constraints

Soil constraints can be any physical or chemical restriction to the normal root proliferation into the subsoil.

Constraints can be naturally occurring, or as a result of management. Soil constraints can often be minimized with the use of correct nutrition or the addition of soil ameliorants.

8. Physiological Factors

The main physiological factors responsible for yield fluctuations are the sensitivity of plants to environmental stress.

The magnitude of crop photosynthesis is primarily determined by the size and longevity of the foliage and, to a lesser extent, by the efficiency of carbon fixation. Water shortage and air temperature strongly affect leaf production, expansion and death.

Flower and pod abortion result from a temporary shortage of assimilates produced by intense intra-plant competition between vegetative parts, especially the stem apex, and reproductive organs at the beginning of flowering. Most of these physiological processes are influenced by the environment.

9. Plant Disease and Insects

Pests and diseases can severely impact plants and contribute to low yields. Crops and plants should be inspected regularly for pests as well as disease and deficiencies.

A combination of biological, chemical and cultural control measures to control pests is considered the most effective and sustainable approach to addressing pest problems.

10. Weeds

Weeds can result in competition with plants or crops species for nutrients and soil moisture. Management strategies in weed control is the integrated approach with the use of herbicides which offers the best approach to reduce the impact of weeds.

In summary, plant structure, growth pattern, organs constitute measureable components of plants.

It is important to remember that while there are many factors that limit plant growth and development, it is equally of note that some of these factors can be managed and manipulated.

The key issue is to identify the most limiting factors and target them with cost-effective strategies in other to optimize yields.

Plant morphology is useful in the visual identification of plants. As plants grow, structures and organs emerge either aerially or subterranean. These will constitute the components that will eventually contribute to final yields of plants. These yields are limited by a number of factors, some of which could be manipulated for optimal yields.

Yield Components of Plant Productivity and Limiting Factors