Apical bud
n., plural: apical buds
/ˈeɪpɪkəl bʌd/
Definition: The primary growing point at the tip of a plant stem
Table of Contents
Apical Bud Definition
The apical bud is the type of bud located at the top (apex) of the plant, particularly at the very tip of the main stem. It represents the growth pinnacle of the plant. It determines the plant’s growth habit and overall form. It is responsible for the plant’s primary growth and apical dominance, particularly in terms of increasing the length or height of the plant. A plant with a strong apical dominance will have the main stem and root elongating rapidly to establish the plant’s basic framework, which is vital when it comes to accessing sunlight for photosynthesis (in the case of stems) and exploring the soil for water and nutrients (in the case of roots).
Etymology: The term “apical” comes from the Latin word “apex,” meaning “tip” or “summit,” emphasizing its location at the tip of the stem.
Synonym: terminal bud; shoot apex; apex bud
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Overview of plant buds
In plants, a bud is a compact meristematic tissue that is yet to develop into a particular plant structure. Thus, we have special terms to pertain to the different types of buds into which the bud will ultimately become. In this regard, buds can be:
- A leaf bud, which develops into a new leaf
- A flower bud, which develops into a flower
- A fruit bud, which develops into a fruit
- A root bud, which develops into a new root
- A mixed bud, which has the potential to develop into both leaves and flowers
- An accessory bud, which develops into specialized structures, such as thorns, tendrils, bulbils, etc.
Another way of classifying buds is based on their position in the plant. We have already mentioned about apical bud found at the very tip of the stem. Other bud types are the axillary buds (lateral buds) located in the axil (the angle between the leaf and the stem). When the bud is located in unusual plant parts that can develop into new shoots or roots, it is referred to as an adventitious bud.
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Apical bud vs. terminal bud
Both terminal bud and apical bud refer to the bud that is located at the end of the plant structure. Thus, they are commonly used interchangeably. However, there are a few times when they are used quite differently, such as in the following context: terminal bud, the bud at the tip or apex of a stem or a branch; apical bud, the bud at the very tip or at the very apex of the main stem or main branch of a plant.
Structure Of Apical Buds
The apical bud is a conical structure comprised of apical meristems. An apical meristem is an undifferentiated tissue located at the tip of the plant (shoot apex) and responsible for the vertical growth of the plant. It consists primarily of cells active in cell division (mitosis).
In vascular plants, the apical meristem will give rise to the three primary meristems:
- The protoderm (which later develops into the epidermis),
- The procambium (develops into vascular tissues or vascular bundle),
- The ground meristem (develops into the cortex and the pith, comprised primarily of ground tissues)
Watch the different zones that make up the shoot apical meristem below.
Shoot Apical Meristem Structure | Plant Biology (by sci-ology):
Functions Of Apical Buds
The apical buds are responsible for the following functions:
- Vertical growth: The apical buds are responsible for the primary growth and the elongation of the main stem. This is where the plant gains height as it reaches towards the sunlight. The apical bud produces auxins, a class of plant hormones, which inhibit the growth of neighboring axillary buds.
- Regulation of lateral growth: Apical buds also control lateral growth by regulating the development of side buds, or axillary buds. The interplay between the apical bud and axillary buds determines the plant’s branching pattern.
NOTE IT!
“Apical Dominance and Revolutionizing Horticulture”
The concept of apical dominance, first proposed by the renowned naturalist Charles Darwin, shed light on a plant’s innate ability to prioritize the growth of its leading or apical bud while controlling the development of lateral buds. Scientists eventually found the reason for this phenomenon, and this is primarily due to the plant hormone auxin.
This hormone produced by the apical bud travels downward. Its action is to inhibit the growth of lateral buds, thus, favoring vertical growth to ensure access to sunlight. Having known the fundamental role of auxin and its interaction with other plant hormones, horticulturists used this insight to come up with simple strategies subject to systematic analysis in plant physiology research so as to manipulate plant growth according to the desired growth patterns.
One practical application is in the art of pruning. By strategically removing the apex responsible for apical dominance, the plant will be stimulated to grow its lateral buds into shoots. As a result, biomass production could be redirected into the desired plant shape and size, which has been proven essential, especially for easy access to fruit trees and landscaping of neighboring plants and trees lining city streets.
“What is Apical Dominance?” (by AgPhD)
References
- Smith, J. D. (2021). “The Role of Apical Buds in Plant Growth.” Journal of Plant Biology, 45(2), 123-135.
- Brown, A. R. (2019). “Apical Buds: Their Significance in Horticulture.” Horticultural Science, 78(4), 321-335.
- University of Georgia. (2007). “Basic Principles of Pruning Woody Plants.” Uga.edu. https://extension.uga.edu/publications/detail.html?number=B949&title=basic-principles-of-pruning-woody-plants#:~:text=By%20removing%20the%20apex%2C%20pruning,to%20the%20root%20system%20(Fig.
- Darwin, C. (1859). “On the Origin of Species by Means of Natural Selection.”
- Went, F. W. (1928). “On the Nature of the Inhibitory Substance in Old Orange Leaves.”
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