Plant Stems Overview

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Questions and Answers

What is the main function of stems in plants?

Gas exchange

Seed germination

Support and growth (correct)

Photosynthesis

Which type of stem consists of soft, nonwoody tissues?

Woody stem

Deciduous stem

Perennial stem

Herbaceous stem (correct)

What feature distinguishes dicot and monocot stems internally?

Type of epidermis

Presence of a central core

Leaf attachment points

Vascular bundle arrangement (correct)

What is the role of lenticels in stems?

Gas exchange Signup and view all the answers

What do bundle scars indicate on a stem?

Vascular tissue attachment Signup and view all the answers

Which part of the stem is responsible for initiating new leaves and buds?

Meristem Signup and view all the answers

What type of tissue is typically found in the hypodermis of a dicot stem?

Collenchyma Signup and view all the answers

Which type of bud is located at the tip of the stem?

Terminal bud Signup and view all the answers

What is the function of the shoot apical meristem (SAM)?

To facilitate rapid elongation of shoots Signup and view all the answers

Which of the following is produced by the vascular cambium?

Secondary xylem Signup and view all the answers

Which of the following best describes the cork cambium?

It forms cork and cork parenchyma for protection. Signup and view all the answers

What does the term 'annual ring' refer to?

The pattern of light and dark cells formed in xylem Signup and view all the answers

Which type of growth results from the activity of lateral meristems?

Secondary growth Signup and view all the answers

What are vascular rays primarily responsible for?

Conducting nutrients and water Signup and view all the answers

Why are primary xylem and phloem replaced by secondary tissues?

To accommodate stem thickening Signup and view all the answers

Which statement is true about monocot and dicot stems?

Both types are commonly found in herbaceous stems. Signup and view all the answers

What is a xylem ray?

Any part of a ray within the xylem Signup and view all the answers

Which stem modification is characterized by its growth parallel to the ground with long internodes?

Runners Signup and view all the answers

What is a characteristic of tubers?

They have a thickened fleshy end for food storage. Signup and view all the answers

Which plant is widely known for its use as a laxative?

Cascara Signup and view all the answers

Which stem modification is known as 'phyllocades'?

Cladophylls Signup and view all the answers

What is the pharmacological use of Chinese rubber tree?

Improves circulation and reduces blood pressure Signup and view all the answers

What distinguishes tunicate bulbs from non-tunicate bulbs?

Outer covering that protects from drying out Signup and view all the answers

What is the main traditional use of Ephedra?

Stimulating breathing Signup and view all the answers

Which of the following plants is used to alleviate nasal stuffiness?

Magnolia officinalis Signup and view all the answers

What is the role of tendrils in plants?

Support for climbing Signup and view all the answers

Study Notes

Plant Stems

Stems are the aerial part of a plant, acting as the axis of the shoot system.
They provide mechanical support to the plant.
They are where leaves and reproductive shoots attach.
They expose leaves and position reproductive shoots for optimal access to pollinators and dispersal agents.

Stem Functions

Support: Providing structural support for the plant.
Conduction: Transporting water and nutrients through xylem and phloem.
Growth: Enabling plant growth.
Storage: Storing food and water, specifically in succulents.

Stem Types

Herbaceous: Composed of thin, soft, non-woody tissues.
Woody: Composed of extensive hard tissues of wood and bark, and are taller and thicker.

Stem External Parts

Bud scale: Outer protective layer covering the terminal bud.
Terminal bud: Tip of the stem.
Terminal bud scale scars: Marks leaves on the stem scars, measuring annual growth.
Axillary bud/leaf scar: Occurs in the leaf axis on the stem's side, indicating previous leaf position.
Lenticels: Pores allowing gas exchange.

Stem Internal Parts (Dicot vs. Monocot)

Epidermis: Present in both, with trichomes sometimes present in dicots.
Cuticle: Present in both.
Hypodermis: Present in dicots, made of collenchyma. Absent in monocots, made of sclerenchyma.
Vascular bundle arrangement: Arranged in a ring/broken rings in dicots; scattered in monocots.
Bundle sheath: Present in monocots, absent in dicots.
Cortex & Stele: Present in dicots, absent in monocots.

Stem Growth (Primary vs. Secondary)

Primary growth: Results from rapidly dividing cells in the apical meristems (shoot and root tips), causing elongation, and the formation of primary meristems (protoderm, procambium, and ground meristem).
Primary meristems development:
- Protoderm → epidermis
- Procambium → primary xylem & phloem
- Ground meristem → pith & cortex
Secondary growth: Increases stem thickness due to lateral meristems (lacking in monocots).
- Vascular cambium: Divides to produce secondary xylem (replacing primary xylem) and secondary phloem (replacing primary phloem).
- Cork cambium: Divides to produce cork cells containing suberin (waxy substance repelling water), resulting in periderm (replacing epidermis).

Stem Modifications

Rhizomes: Thickened underground stems with distinct nodes and internodes, and scaly leaves.
Runners: Stems growing parallel to the ground, creeping, with long internodes, developing from the axils of lower leaves of the aerial stem.
Stolons: Produced beneath the surface of the ground, used to produce new plants.
Stem tendrils: Slender twining strands enabling climbing plants to seek support.
Corms: Short, vertical, swollen underground stems, serving as food storage organs.
Cladophylls: Green, flattened, cylindrical stems resembling leaves, performing photosynthesis.
Tubers: Rhizome's thickened end, fleshy, enlarged for food storage.
- Tunicate: Has a papery outer covering protecting from damage.
- Non-tunicate: Does not have a protective outer covering.
- Bulbs: Modified underground buds that are short stems covered by paper-like bulb scales, modified leaves, often used for food storage.

Stems in Pharmaceuticals

Specific plant stems are valued for their medicinal properties

Wood Structure

Annual rings: Alternating concentric rings of light and dark cells over a period of years, reflecting seasonal growth variations.
Vascular rays: Consist of parenchyma cells, responsible for conducting nutrients and water and storing food.
Xylem rays part of a ray within the xylem.
Phloem rays extension of phloem ray through the phloem.

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Description

Explore the vital role of stems in plant structure and function. This quiz covers different stem types, their external parts, and their essential functions, such as support, conduction, growth, and storage. Test your knowledge on how stems contribute to the overall health and productivity of plants.