pertumbuhan primer dan sekunder

Summary

In this biology class, the concepts of primary and secondary growth in plants are discussed. Primary growth refers to the upward elongation of the plant, occurring through the activity of the apical meristem at the tips of stems and roots. Secondary growth, in contrast, involves an increase in diameter and occurs due to the lateral meristem or cambium. The vascular cambium forms secondary xylem and phloem, while the cork cambium forms bark. Unique to grasses, intercalary meristems contribute to segment formation in stems. This lesson provides a detailed look at the key growth processes in plants.

Takeaways

• 🌱 Primary growth refers to the upward growth of plants, occurring due to the activity of the apical meristem at the tips of the stem and root.
• 🌿 The apical meristem is a tissue located at the tips of stems and roots that is responsible for primary growth.
• 🌳 The primary growth of the stem includes leaf primordial (leaf primordia), apical meristem, protoderm, procambium, and basic meristem.
• 🌾 In roots, primary growth includes the root cap, apical meristem, elongation zone, differentiation zone, and root hair formation.
• 💧 Root hairs are responsible for increasing water absorption, while the root cap helps penetrate the soil and produces mucus to ease this process.
• ⛅ Secondary growth occurs in width or diameter, facilitated by the lateral meristem, or cambium, allowing the plant to grow thicker.
• 🌳 Not all plants undergo secondary growth; only gymnosperms and dicotyledonous plants have cambium capable of this process.
• 🌿 The vascular cambium in secondary growth produces secondary xylem inward and secondary phloem outward, creating annual rings in trees.
• 🍂 Cork cambium (or phellogen) replaces damaged epidermis with cork cells outward and phelloderm inward, protecting plants from environmental damage.
• 🌾 Intercalary meristems, found in plants like grasses and bamboo, allow for rapid growth and formation of segments along the stem.
• 🌳 The overall function of secondary growth is to increase plant girth and protect the plant, especially by forming bark or cork to replace damaged epidermis.

Q & A

What is primary growth in plants?

Primary growth is the upward growth of a plant, increasing its length. It occurs due to the activity of the apical meristem located at the tips of the stem and root.

Where is the apical meristem located?

The apical meristem is found at the tips of the stem and root. It is responsible for primary growth and is crucial for elongation.

What is the function of the root cap (calyptra)?

The root cap (calyptra) protects the growing tip of the root and helps the root penetrate the soil. It also produces mucus to moisten the soil, aiding root growth.

What are the main zones of the root tip?

The root tip consists of the root cap, the apical meristem zone, the elongation zone, and the differentiation (or maturation) zone, where root hairs form.

What is the role of root hairs in plants?

Root hairs are responsible for increasing water absorption from the soil, essential for the plant's nutrient intake.

What is secondary growth in plants?

Secondary growth is the increase in the width or diameter of a plant. It occurs due to the activity of lateral meristems like cambium and is seen in some plants, especially gymnosperms and dicotyledons.

Which plants exhibit secondary growth?

Secondary growth occurs in gymnosperms (open seed plants) and dicotyledonous plants (those with two cotyledon seeds).

What is the function of vascular cambium?

The vascular cambium produces secondary xylem (wood) inward and secondary phloem outward. This results in the thickening of the plant body and the formation of annual growth rings.

What is the role of cork cambium or phellogen?

Cork cambium produces cork cells outward and phelloderm inward. It replaces the damaged epidermis, protecting the plant from water loss and infections.

What are intercalary meristems and in which plants are they found?

Intercalary meristems are found in grasses, such as bamboo. They contribute to the formation of segments along the stem, aiding in the plant's growth.