With its vibrant green foliage and easy care requirements, it’s no wonder the arrow plant, or Syngonium podophyllum, is a popular houseplant. But what’s going on below the soil and inside those fleshy stems that gives this tropical beauty its structure and helps it thrive? Join me as we explore arrow plant anatomy, including the roots, stems, and how each part functions to support healthy growth.
Arrow Plant Roots: The Foundation of Growth
Like most plants, arrow plants have a root system that anchors them in place, absorbs water and nutrients, and stores food reserves Here are some key facts about arrow plant roots
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Root structure – Arrow plants have a fibrous root system made up of many fine lateral roots that spread out from the base of the main stem.
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Root depth & spread – Arrow plant roots grow 12-18 inches deep and spread 12-24 inches outward. The extensive root system provides excellent stability.
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Root hairs – Tiny root hairs located along the roots maximize the plant’s ability to absorb water and dissolved minerals from the soil.
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Root growth – The roots grow quickly in response to regular watering and fertilizing during the active growing season.
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Food reserves – Arrow plant roots store starch as an energy reserve for new growth after periods of dormancy.
The Hardy Arrow Plant Stem
The stem, or trunk, of the arrow plant does much more than just hold those pretty leaves up. Here’s a closer look:
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Stem structure – Arrow plant stems are comprised of nodes (joint points) and internodes (segments between nodes).
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Stem shape – Arrow plant stems are thick, soft, and succulent with a bumpy texture. The stems are green when new but mature to brown.
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Stem growth – New stems sprout from rhizomes under the soil. As lower leaves drop off, the stem hardens and takes on a woody appearance.
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Nodes – Leaf scars and aerial roots emerge from nodes. Nodes contain meristem tissue which facilitates new growth.
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Internodes – The segments between nodes elongate as the stem grows taller. Leaves emerge from the tip of each internode.
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Aerial roots – Arrow plants sprout thick aerial roots from the stem nodes. These help support and stabilize tall growth.
How Arrow Plant Parts Work Together
Now that we’ve explored the parts, let’s look at how the roots and stems work together to benefit the plant:
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Water and nutrient absorption – The extensive root system efficiently absorbs moisture and dissolved minerals to nourish the plant.
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Anchorage – The roots anchor the arrow plant in place while the stem provides vertical support against gravity and wind.
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Energy storage – Food reserves in the roots sustain new growth when leaves are shed. Stem nodes also store energy.
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New growth – Meristem tissues in the stem nodes and root tips perpetuate plant growth. Roots and shoots proliferate from this tissue.
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Reproduction – Adventitious shoots called plantlets emerge from stem nodes, allowing propagation without seeds.
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Drought tolerance – Fleshy stems and extensive roots store water to withstand short periods of drought.
With its dynamic root and stem systems working together seamlessly, the arrow plant is well-equipped for vigorous growth, self-propagation, and moderate stress tolerance. Understanding what lies beneath the soil surface provides helpful caregiving insights for this delightful houseplant.
Leaf Structure and Function
The outermost layer of the leaf is the epidermis; it is present on both sides of the leaf and is called the upper and lower epidermis, respectively. Botanists call the upper side the adaxial surface (or adaxis) and the lower side the abaxial surface (or abaxis). The epidermis helps in the regulation of gas exchange. It contains stomata (Figure 16): openings through which the exchange of gases takes place. Two guard cells surround each stoma, regulating its opening and closing.
The epidermis is usually one cell layer thick; however, in plants that grow in very hot or very cold conditions, the epidermis may be several layers thick to protect against excessive water loss from transpiration. A waxy layer known as the cuticle covers the leaves of all plant species. The cuticle reduces the rate of water loss from the leaf surface. Other leaves may have small hairs (trichomes) on the leaf surface. Trichomes help to deter herbivory by restricting insect movements, or by storing toxic or bad-tasting compounds; they can also reduce the rate of transpiration by blocking air flow across the leaf surface (Figure 17).
Below the epidermis of dicot leaves are layers of cells known as the mesophyll, or “middle leaf.” The mesophyll of most leaves typically contains two arrangements of parenchyma cells: the palisade parenchyma and spongy parenchyma (Figure 18). The palisade parenchyma (also called the palisade mesophyll) has column-shaped, tightly packed cells, and may be present in one, two, or three layers. Below the palisade parenchyma are loosely arranged cells of an irregular shape. These are the cells of the spongy parenchyma (or spongy mesophyll). The air space found between the spongy parenchyma cells allows gaseous exchange between the leaf and the outside atmosphere through the stomata. In aquatic plants, the intercellular spaces in the spongy parenchyma help the leaf float. Both layers of the mesophyll contain many chloroplasts. Guard cells are the only epidermal cells to contain chloroplasts.
In the leaf drawing (Figure 18a), the central mesophyll is sandwiched between an upper and lower epidermis. The mesophyll has two layers: an upper palisade layer comprised of tightly packed, columnar cells, and a lower spongy layer, comprised of loosely packed, irregularly shaped cells. Stomata on the leaf underside allow gas exchange. A waxy cuticle covers all aerial surfaces of land plants to minimize water loss. These leaf layers are clearly visible in the scanning electron micrograph (Figure 18b). The numerous small bumps in the palisade parenchyma cells are chloroplasts. Chloroplasts are also present in the spongy parenchyma, but are not as obvious. The bumps protruding from the lower surface of the leave are glandular trichomes, which differ in structure from the stalked trichomes in Figure 17.
Like the stem, the leaf contains vascular bundles composed of xylem and phloem (Figure 19). The xylem consists of tracheids and vessels, which transport water and minerals to the leaves. The phloem transports the photosynthetic products from the leaf to the other parts of the plant. A single vascular bundle, no matter how large or small, always contains both xylem and phloem tissues.
Coniferous plant species that thrive in cold environments, like spruce, fir, and pine, have leaves that are reduced in size and needle-like in appearance. These needle-like leaves have sunken stomata and a smaller surface area: two attributes that aid in reducing water loss. In hot climates, plants such as cacti have leaves that are reduced to spines, which in combination with their succulent stems, help to conserve water. Many aquatic plants have leaves with wide lamina that can float on the surface of the water, and a thick waxy cuticle on the leaf surface that repels water.
Watch “The Pale Pitcher Plant” episode of the video series Plants Are Cool, Too, a Botanical Society of America video about a carnivorous plant species found in Louisiana.
Leaves are the main site of photosynthesis. A typical leaf consists of a lamina (the broad part of the leaf, also called the blade) and a petiole (the stalk that attaches the leaf to a stem). The arrangement of leaves on a stem, known as phyllotaxy, enables maximum exposure to sunlight. Each plant species has a characteristic leaf arrangement and form. The pattern of leaf arrangement may be alternate, opposite, or spiral, while leaf form may be simple or compound. Leaf tissue consists of the epidermis, which forms the outermost cell layer, and mesophyll and vascular tissue, which make up the inner portion of the leaf. In some plant species, leaf form is modified to form structures such as tendrils, spines, bud scales, and needles.
The roots of seed plants have three major functions: anchoring the plant to the soil, absorbing water and minerals and transporting them upwards, and storing the products of photosynthesis. Some roots are modified to absorb moisture and exchange gases. Most roots are underground. Some plants, however, also have adventitious roots, which emerge above the ground from the shoot.
Structure of a Typical Leaf
Each leaf typically has a leaf blade called the lamina, which is also the widest part of the leaf. Some leaves are attached to the plant stem by a petiole. Leaves that do not have a petiole and are directly attached to the plant stem are called sessile leaves. Small green appendages usually found at the base of the petiole are known as stipules. Most leaves have a midrib, which travels the length of the leaf and branches to each side to produce veins of vascular tissue. The edge of the leaf is called the margin. Figure 13 shows the structure of a typical eudicot leaf.
Within each leaf, the vascular tissue forms veins. The arrangement of veins in a leaf is called the venation pattern. Monocots and dicots differ in their patterns of venation (Figure 14). Monocots have parallel venation; the veins run in straight lines across the length of the leaf without converging at a point. In dicots, however, the veins of the leaf have a net-like appearance, forming a pattern known as reticulate venation. One extant plant, the Ginkgo biloba, has dichotomous venation where the veins fork.
The arrangement of leaves on a stem is known as phyllotaxy. The number and placement of a plant’s leaves will vary depending on the species, with each species exhibiting a characteristic leaf arrangement. Leaves are classified as either alternate, spiral, or opposite. Plants that have only one leaf per node have leaves that are said to be either alternate—meaning the leaves alternate on each side of the stem in a flat plane—or spiral, meaning the leaves are arrayed in a spiral along the stem. In an opposite leaf arrangement, two leaves arise at the same point, with the leaves connecting opposite each other along the branch. If there are three or more leaves connected at a node, the leaf arrangement is classified as whorled.
Leaves may be simple or compound (Figure 15). In a simple leaf, the blade is either completely undivided—as in the banana leaf—or it has lobes, but the separation does not reach the midrib, as in the maple leaf. In a compound leaf, the leaf blade is completely divided, forming leaflets, as in the locust tree. Each leaflet may have its own stalk, but is attached to the rachis. A palmately compound leaf resembles the palm of a hand, with leaflets radiating outwards from one point Examples include the leaves of poison ivy, the buckeye tree, or the familiar houseplant Schefflera sp. (common name “umbrella plant”). Pinnately compound leaves take their name from their feather-like appearance; the leaflets are arranged along the midrib, as in rose leaves (Rosa sp.), or the leaves of hickory, pecan, ash, or walnut trees.
Plant Root System & Shoot System
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