Questions and Answers
What type of placenta is formed when ovules are attached in a multi-locular ovary?
What is the term for a fruit that develops without fertilization of the ovary?
Which part of a seed is known as the scar through which it was attached to the fruit?
What layer of the pericarp is located on the outer side?
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Which structure of a dicotyledonous seed stores food and is formed as a result of double fertilization?
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What is the primary function of xylem fibers in plants?
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Which component of phloem is responsible for the translocation of food?
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What characteristic distinguishes the cells in the dermal tissue system?
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What is the role of companion cells in the phloem?
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Which of the following is not a function of dermal tissue?
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Study Notes
Xylem Components
- Xylem fibers are elongated, lignified, and pointed at both ends.
- Xylem functions include conducting water and nutrients from roots to leaves and providing mechanical support.
- Xylem parenchyma consists of living, thin-walled cells primarily involved in storing starch and fatty substances.
Phloem Components
- Phloem consists of four main elements: sieve tubes, companion cells, phloem fibers, and phloem parenchyma.
- Sieve tubes are elongated, tubular cells with perforated walls and facilitate food translocation from leaves to storage organs.
- Companion cells, which are elongated, support the function of sieve tubes, predominantly found in angiosperms.
- Phloem parenchyma consists of living cells and is responsible for storing food materials.
- Phloem fibers are long and lignified, providing additional mechanical strength.
Dermal Tissue System
- Dermal tissue acts as the outer covering of plants, forming a protective barrier and controlling environmental interactions.
- The epidermis is typically one layer thick and covers all primary plant structures, lacking chloroplasts.
- Periderm refers to tissues that replace the epidermis in woody plants, particularly in older stems.
Fruit and Seed Structure
- A fruit, characteristic of angiosperms, develops from a mature ovary post-fertilization; parthenocarpic fruits form without fertilization.
- Fruits consist of pericarp (the fruit wall) and seeds, with pericarp varying between dry and fleshy types.
- Seeds develop from ovules post-fertilization and consist of a seed coat and an embryo, which comprises radicle, embryonal axis, and cotyledons.
- Dicotyledonous seeds have a seed coat made of two layers, hilum (attachment point), micropyle (small opening), and food-storing endosperm.
Root Modifications
- Roots may undergo modifications for various functions:
- Food storage: roots become swollen to store nutrients.
- Support: prop roots and stilt roots provide stability for plants.
- Respiration: pneumatophores facilitate oxygen intake for plants in swampy areas.
Plant Tissue Systems
- Plant tissues are organized into three systems: epidermis (outer surface), ground tissue (nutrient manufacture and storage), and vascular tissue (xylem and phloem for nutrient transport).
- Tissues are further divided into meristematic (actively dividing) and permanent tissues (specialized functions).
Meristematic Tissue
- Meristems, located at growing tips (apical), sides (lateral), and base (intercalary), contribute to primary and secondary plant growth.
- Apical meristems lead to vertical growth, while lateral meristems increase the girth of plants.
Permanent Tissue
- Permanent tissues arise from meristematic tissues and can be simple (uniform cells) or complex (mixed cell types).
- Simple permanent tissues include parenchyma (storage and photosynthesis), collenchyma (structural support), and sclerenchyma (strength).
Functions of Parenchyma
- Parenchyma is found in various plant parts, storing substances like starch and oils and participating in photosynthesis.
- It facilitates wound repair and renews meristematic activity and aids in gas exchange (aerenchyma) for aquatic plants.
Functions of Collenchyma and Sclerenchyma
- Collenchyma cells offer structural support in young plant parts, characterized by thickened primary walls.
- Sclerenchyma provides rigidity throughout the plant body, composed of thickened cell walls to withstand mechanical stress.
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Description
Explore the fascinating components of xylem in plants, including xylem fibers and parenchyma. Learn about their roles in conducting water and nutrients, as well as providing mechanical support. Test your understanding of plant anatomy and functions.
