Feature : Ginkgo (Ginkgo biloba) leaves that were shed from trees in the fall. Ginkgo leaves have dichotomous venation, or a pattern of venation in which the veins fork one or more times. Credit: E.J. Hermsen (DEAL).
The bay leaf plant also known as bay laurel or Laurus nobilis is an aromatic evergreen herb that is grown both for its culinary uses and ornamental merits. While the leaves are the most utilized part of the plant, the roots and stems also play important roles in the growth, function, and health of the bay leaf plant. In this article, we will take a deep dive into bay leaf plant anatomy, specifically exploring the key features and functions of the roots and stems.
Bay Leaf Plant Basics
Before looking at the specific parts let’s review some background on the bay leaf plant itself.
- Originated in the Mediterranean region
- Can grow up to 10-30 feet tall in ideal conditions
- Has an erect, columnar shape with a bushy head
- Features thick, leathery leaves that are very aromatic
- Grows slowly and can live for years if cared for properly
- Thrives in warm, humid environments with well-draining soil
Both the leaves and the essential oils they contain are used for cooking medicine cosmetics and more. The plants are also commonly grown ornamentally in gardens given their attractive form and fragrance. Now, let’s explore the key anatomical features that allow bay plants to grow and thrive.
The Root System
A plant’s roots are critically important, serving functions such as:
- Anchoring and supporting the plant in the ground
- Absorbing water and nutrients from the soil
- Storing reserves of nutrients and carbohydrates
- Allowing propagation through suckers and shoots
Bay leaf plants have a taproot system consisting of a central, dominant taproot that grows vertically downward, with smaller lateral roots radiating out horizontally from the sides.
- The taproot anchors the plant and stores energy reserves.
- Lateral roots gather water and soil nutrients.
- This root structure provides strength and stabilization.
In ideal growing conditions, bay laurel taproots can grow very deep, up to 6 feet into the ground. This allows them to anchor the plant firmly and access water far below the surface.
Stem Anatomy
The stems of bay leaf plants perform a number of vital functions:
- Provide structural support for leaves and branches
- Transport water, minerals and nutrients
- Store nutrients and create new living tissue
- Enable translocation and growth
The stems have the following key anatomical features:
- Comprised of nodes (points connecting to leaves) and internodes
- Covered by a thin, greenish bark
- Contain vascular tissue for transporting water and nutrients
- Arrangement of vascular bundles depends on stem age and diameter
- Woody and rigid, providing strong support
As bay plants mature, the stems thicken and become more woody. The bark develops fissures and small ridges characteristic of bay laurel trees. Proper stem growth results in a attractive columnar shape.
How Roots and Stems Work Together
The root and stem systems work closely together to facilitate healthy growth:
- Roots take up water and minerals and send them to the stem
- The stem transports these essential elements to the leaves
- Leaves produce food via photosynthesis and deliver sugars to the stem
- Stems move sugars and nutrients to the roots for storage
- This circulating pathway allows the exchange of vital substances
This interconnected relationship between roots and stems enables bay plants to thrive. Disruption of either system will compromise the health of the plant.
Propagation Using Stem Cuttings
An important function of bay leaf stems is vegetative reproduction through stem cuttings:
- Cuttings allow gardeners to easily propagate new bay leaf plants
- Cuttings are taken from the tips of mature stems
- Each cutting should have 2-3 leaf nodes to allow new root growth
- The lower leaves are removed and the cut end is dipped in rooting hormone
- Cuttings are planted in potting mix and kept humid until roots develop
- Once roots are established, the new plant can be repotted
This method of propagation produces genetic clones of the parent plant quickly and efficiently.
Signs of Unhealthy Roots or Stems
Some signs that the root or stem systems have been damaged or compromised:
Roots:
- Stunted growth
- Wilting of leaves
- Leaf drop
- Failure to bloom
Stems:
- Weak, drooping stems
- Withered leaves
- Dieback of shoots or branches
- Bark lesions or splitting
Addressing issues with roots and stems quickly is key to restoring plant health. This may involve pruning damaged areas, amending soil, adjusting watering or fertilization, or repotting the plant.
Key Takeaways on Bay Leaf Plant Anatomy
- A deep taproot provides anchorage while lateral roots absorb nutrients
- Stems contain vascular tissue for transporting water and sugars
- Roots and stems work closely together to facilitate growth
- Stem cuttings allow easy propagation of new bay plants
- Discoloration or damage to roots and stems indicates plant stress
The intricate root and stem systems work continuously to keep bay leaf plants healthy and functioning optimally. Understanding the anatomy and growth habits of Laurus nobilis helps guide proper care for maximum vitality. With the right growing conditions, the bay leaf plant will thrive for years to come.
The origins of leaves
Two basic types of leaves occur in vascular plants, microphylls (Greek mikros + phyllon = small leaf) and megaphylls (Greek megas + phyllon = large leaf). These terms are used to distinguish leaf types that differ in their evolutionary origins and, often, their structural attributes. Some scientists have criticized these terms as confusing because small, simple megaphylls look similar to microphylls. Furthermore, the terms are sometimes used in a purely descriptive way with no evolutionary implications. Thus, it has been proposed that the two major leaf types in vascular plants instead be called lycophylls (= microphylls) and euphylls (= megaphylls).
Microphylls are the leaves of lycophytes. These leaves lack a stalk (petiole or stipe), are simple in form (often scale-like or strap-shaped), and typically have a single vein that does not branch. Because lycophytes have stems with protosteles, microphylls are not associated with leaf gaps (a leaf gap is a gap in the stem vascular tissue that occurs above the point at which a leaf trace departs).
Megaphylls are the leaves of euphyllophytes. Megaphylls are highly diverse in form and may have complex venation; however, in some taxa like horsetails (Equisetum) and many conifers (like pines, Pinus), megaphylls are small with very simple venation and resemble microphylls. Typically, megaphylls are associated with leaf gaps because they are found in plants that have stems with siphonosteles (vascular tissue forms an open cylinder around a pith) or eusteles (vascular tissue occurs in separate bundles).
Microphylls have evolved once in vascular plants and are a synapomorphy for the lycophytes. Megaphylls have evolved more than once in euphyllophytes, so they are not a true synapomorphy for the whole group. (For this reason, it has been proposed that the “megaphyll” or “euphyll” concept be abandoned altogether—see here). However, overtopping, one of the early steps in the hypothesized evolution of the megaphyll (see below), is considered a synapomorphy for euphyllophytes.
Origins of leaves. The tree of living tracheophyte (vascular plant) relationships above shows key steps in the origins of leaves. Microphylls are a synapomorphy for the lycophytes. Overtopping, one of the steps in the hypothesized origin of megaphylls, is a synapomorphy for euphyllophytes. Credit: E.J. Hermsen (DEAL).
The theory that explains the origin of microphyll is the enation theory. Under this theory, microphylls evolved from structures known as enations, which are flap-like outgrowths of the stem that lack vascular tissue. The steps in this theory are as follows:
- Plants have naked aerial axes (stems) with no outgrowths.
- Origin of enations: Flap-like outgrowths develop on aerial axes (stems).
- Leaf traces: Leaf traces develop, but do not enter the enation.
- Leaf vascularization: The enations become vascularized and can be called leaves.
Enation theory for origin of microphylls (lycophylls). The steps in the enation theory, which is a theory for the origin of lycophyte leaves, is as follows: 1. Leafless axis (the vascular tissue is represented by the vertical yellow stripe). 2. Axis with an enation; note that no vascular tissue diverges toward the enation. 3. A leaf trace diverges toward the enation, but does not enter it. 4. Vascular tissue enters the enation, which is now a leaf. Credit: Diagram by E.J. Hermsen (DEAL). After fig. 3-9 in Gifford & Foster (1974), among other sources.
The classical explanation for the origin of megaphylls is the telome theory. This theory proposes that megaphylls evolved from branching systems. The steps in the evolution of the megaphyll under the telome theory are as follows:
- Plants have axes (stems) with equal dichotomous branching.
- Overtopping: Branching becomes unequal so that plants have a dominant stem bearing branching systems.
- Planation: The branching systems became planar (flattened).
- Webbing: A lamina (flat sheet of tissue) develops between branches to form a leaf.
Telome theory for origin of megaphylls (euphylls). The steps in the telome theory, which is a theory for the origin of euphyllophyte leaves, is as follows: 1. Axis with equal dichotomous, three-dimensional branching. 2. Axis with unequal branching; one branch is dominant whereas the others form subordinate branching systems. 3. Lateral branching systems become flattened (planar). 4. Webbing develops between branches, forming a leaf. Credit: Diagram by E.J. Hermsen (DEAL). After fig. 1 in Rothwell et al. (2014), among other sources.
Microphylls vs. Megaphylls
| Microphylls | Megaphylls | |
|---|---|---|
| Alternate name | Lycophylls | Euphylls |
| Plant group | Lycophytes | Euphyllophytes |
| Evolution | From enations | From branching systems |
| Number of independent originations | One | More than one |
| Leaf stalk | Absent, leaf scale-like | Absent or present |
| Leaf venation | Usually one unbranched vein | Variable, venation often branching |
| Associated stele type | Protostele | Usually siphonostele or eustele |
| Associated leaf gaps | Absent | Usually present |