Anatomy of Plants

Flowers aren’t merely pretty to look at. They serve a variety of roles in addition to their beauty and scent. To begin with, they are a plant’s reproductive organ. They are made up of a variety of structures that aid the plant’s survival, growth, and reproduction.

All of a plant’s parts are made up of cells because it is a living thing. Plant cells, like animal cells, have a flexible membrane, but they also have a strong cellulose wall that gives them a solid form. Plant cells, unlike animal cells, have chloroplasts, which capture the Sun’s light energy and turn it into food. A plant, like any other complex living organism, organizes specialized cells into tissues that serve a specific purpose.

Let’s have a look at flowering plants’ anatomy.

THE TISSUES

A tissue is a collection of cells that share a same origin and typically execute the same function. A plant is made up of various sorts of tissues. Tissues are divided into two categories: meristematic and permanent tissues, depending on whether or not the cells forming them are capable of dividing.

• Meristematic Tissue is composed of a collection of cells with the potential to divide. These tissues are made up of tiny, cuboidal, tightly packed cells that continue to divide and create new ones. As they age, these tissues are capable of extending, expanding, and differentiating into distinct types of tissues. Permanent tissues develop from meristematic tissues. Apical meristems, lateral meristems, and intercalary meristems are the three types of merismatic tissues, depending on where they are found.

• Permanent Tissue is made up of merismatic tissues that have lost the ability to divide. They’ve reached their full potential. The plant’s permanent tissues make up the majority of its structure.

The two types of permanent tissues are simple and complicated. 

Simple Permanent tissues

• Parenchyma– The soft sections of a plant, like the roots, stems, leaves, and flowers, include these tissues. This tissue’s cells are loosely packed, with vast intercellular spaces between them. A vacuole is located at the center of each cell. Storage, photosynthesis, and helping the plant float on water are all activities of parenchyma tissues.

• Collenchyma- With thicker cell walls, they are similar to parenchyma cells. They’re designed to provide mechanical support to the plant’s structure in places like the leaf’s petiole.

• Sclerenchyma- This tissue’s cells have died. They have thick, lignified secondary walls and are stiff. Their primary purpose is to offer strength and support to plant sections.

Complex Permanent Tissue

Complex permanent tissues, unlike simple permanent cells that all appear the same and are made up of the same type of cells, are made up of multiple types of cells. These several cell types work together to complete a task. Xylem and Phloem are complex permanent tissues present in the plant’s vascular bundles.

• Xylem- Tracheids, vessels, xylem parenchyma, and xylem fibres make up the xylem parenchyma. Tracheids and vessels are hollow tube-like structures that aid in water and mineral transport. The xylem only transports water vertically. The cooked meal is stored in the xylem parenchyma, which also aids in water conduction. In terms of function, xylem fibers are helpful.

• Phloem- Sieve tubes, companion cells, phloem fibers, and the phloem parenchyma are the four components. Phloem, unlike xylem, conducts in both directions. It’s in charge of delivering food from the leaves to the rest of the plant. Except for fibers, which are dead tissues, phloem contains living tissues.

Tissue System

Epidermal Tissue System:  It includes the epidermis, cuticle, stomata, epidermal extensions, and trichomes in stem and root hairs, as well as the plant’s exterior covering, such as epidermis, cuticle, stomata, and epidermal extensions.

• Through transpiration, stomata regulate gaseous exchange and water loss.
• In dicots, guard cells are bean-shaped and contain chloroplasts.
• Grasses have guard cells that are formed like a dumbbell.
• Root hairs are single-celled.
• Trichomes are a multicellular organism.

The ground Tissue System: They make up the bulk of tissues that lie between epidermal and vascular tissues, such as the cortex, pericycle, and pith. It includes basic tissues. Mesophyll is a ground tissue with chloroplast in leaves.

The Vascular Tissue System

• It consists of complex xylem and phloem tissues.

• Cambium is found between the xylem and phloem of the vascular bundle in dicots

• Cambium creates secondary vascular tissues

• Dicots have a vascular bundle that is open.

• There is no cambium in monocots since their vascular bundle is closed.

• • In roots, the vascular bundles are organized in a radial pattern, with xylem and phloem alternately present.

• • The stem and leaf vascular bundles are grouped together, i.e. At the same radius, xylem and phloem are found.

ANATOMY OF DICOTYLEDONOUS AND MONOCOTYLEDONOUS PLANTS

For a better knowledge of root, stem, and leaf tissue organization.

Dicotyledonous Root: Epiblema is the topmost layer. Epiblema cells frequently emerge in the form of unicellular root hairs. Endodermis refers to the cortex’s deepest layer. It is made up of a single layer of barrel-shaped cells with no intercellular gaps between them. Pericycle is a layer of thick-walled parenchyomatous cells that is next to endodermis. The parenchymatous cells that make up conjunctive tissue are found between the xylem and the phloem. Xylem and phloem patches are usually two to four in number. Later, between the xylem and the phloem, a cambium ring forms. 

Monocotyledonous Root: The monocot root frequently possesses more than six (polyarch) xylem bundles in compared to the dicot root, which has fewer. The pith is substantial and well-developed. secondary growth is not experience by Monocot roots.

Dicotyledonous Stem

• The epidermis has a cuticle and may have trichomes and stomata. 

• The cortex has three layers: the outermost hypodermis (collenchymatous), the middle parenchymatous cortical layer, and the endodermis containing starch grains.

• Pericycle and radially placed medullary rays are present beneath the endodermis.

• The vascular bundles form a ring.

Monocotyledonous Stem

• Vascular bundles are dispersed, conjoint, and closed 

• Hypodermis is sclerenchymatous

(a) Dicot stem  

(b)  Monocot stem

Dicotyledonous Leaf

• Due to the different dorsal and ventral sides, this leaf is also referred to as dorsiventral leaf.

• Reticulate venation

• Both the upper and bottom surfaces are covered by the epidermis.

• Vascular bundles are surrounded by bundle sheath cells and present on veins and mid-rib

• The epidermis covers both the upper and below surface and is also known as dorsiventral leaf because of the separate dorsal and ventral sides.

• Photosynthesis is carried out by mesophyll cells, which are parenchymatous.

• Elongated palisade and oval or round spongy parenchyma cells make up the mesophyll.

• Vascular bundles are found on veins and in the mid-rib and are encircled by bundle sheath cells.

Monocotyledonous Leaf

• Parallel venation 

• Equally distributed stomata on both sides 

• Also known as isobilateral because both sides are identical

• There is no difference in the mesophyll between palisade and spongy parenchyma cells.

• In grasses, some epidermal cells are transformed into giant cells known as bulliform cells, which aid in water conservation.

The size of the vascular bundles is the same.

(a) Dicot Leaf

(b) Monocot Leaf

Secondary Growth

• A ring of cambium is formed in the dicot stem from intrafascicular cambium present between xylem and phloem and the medullary cells present beside the two vascular bundles that become meristematic due to dividing lateral meristems; vascular and cork cambium

• Cambium is most active in the spring, producing earlywood or springwood, which has more xylary components, is lighter in color, and has a low density.

• Autumn wood, also known as latewood, is formed when the cambium is less active in the winter. In the fall, the trees are thick and dark in color.

• These produce alternate bright and dark annual rings, which can be used to estimate a tree’s age.

• Tannins, raisins, oils, and gums are deposited in the secondary xylem, forming heartwood. It’s tough, long-lasting, and insect-resistant.

• Sapwood is the lighter-colored outer portion of secondary xylem that transports water.

• The outer cortex is where cork cambium grows. Phellogen is another name for it.

• Cork’s cell wall is waterproof due to suberin deposition.

• Bark refers to all tissue outside of the vascular cambium, including secondary phloem.

• Lenticels, which are found on the epidermis, aid in gas exchange.

• Monocots do not have secondary growth, whereas gymnosperms do.

Secondary growth in Dicot Stem 

Reproductive anatomy

The flower is angiosperms’ most distinguishing characteristic. Flowers are the most dependable exterior features for recognizing angiosperm species connections since they come in a wide range of shapes and elaboration. It is the responsibility of the flower to ensure that the ovule is fertilized and that fruit containing seeds develops. The floral apparatus can arise from the leaf axil or the stalk’s terminal (where the petiole attaches to the stem). Violets, for example, have solitary blooms that develop in the axil of a regular foliage leaf. The flower-bearing element of the plant is usually distinguished from the foliage-bearing or vegetative component, and forms an inflorescence, which is a more or less complex branch system.

Two types of reproductive cells develop in flowers. Microspores divide to produce pollen grains, which are carried in the stamens by the “male” cells (or microsporophyll’s). Megaspores, or “female” cells, are caught in the ovule and enclosed in the carpel, where they will divide into egg cells (mega gametogenesis) (or megasporophyll).

CONCLUSION

From an anatomical aspect, a plant is made up of various tissues. Meristematic (apical, lateral, and intercalary) and permanent (apical, lateral, and intercalary) tissues are the two types of plant tissues (simple and complex). Food processing and storage, water movement, mineral and photosynthetic transmission, and mechanical integrity are all important functions of tissues. Secondary growth is induced in most dicotyledonous roots and stems by the activity of the vascular and cork cambiums, increasing the girth (diameter) of the organs. The wood is a type of secondary xylem. Many different types of wood exist, depending on its content and production schedule.