Class notes
Intro to Plant Sciences notes/quizzes
- Course
- BOT 3015 (BOT3015)
- Institution
- University Of Central Florida
Roots, Stems, and Leaves notes as well as 3 quiz questions and answers with relevant information.
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Morphology vs. Anatomy:● Plant morphology: The study of the physical form and external structure of plants.
○ Observation and classification of plant organs and their arrangement.
○ Identification and categorization of plants based on external features.
○ Usual for taxonomy and systematics.
● Plant anatomy: the study of the issues and cell structures of plant organs.
○ Microscopic examination of plant cells and their organization WITHIN the plant.
Roots functions:
1. Anchorage to the soil
2. Support of the shoot system
3. Absorption of water and mineral
4. Storage of food
- Balance between shoot and root - for sufficient supply of water and minerals (in
herbaceiys plants, water makes up about 90% of plant weight)
Rhizosphere: thin area around roots - where complex chemistry occurs for nutrient absorption.
Root development:
1. Many important functions take place near the tips, including growth and absoprtion.
2. Zone of division: root apical meristem divides to create primary meristematic tissue:
protected by root cap.
3. Zone of elongation: newly divided cells grow longitudinally while cell wall remains
flexible. Here, primary meristematic tissues are formed.
4. Zone of maturation: root hairs form and help absorb water and minerals. Branching
starts here.
Quiescent center: area of the RAM that divides at an extremely slow rate.
Root cap: cells are constantly removed and replaced by apical meristem.
- Site of gravity perception.
Pericycle: the zone of root branching.
Root primary tissues:
1. Epidermis: a single layer of cells at outer boundary - arises from protoderm.
a. External wall of epidermal cells might elongate into root hairs.
i. Sticky - soil particles stick to them
ii. Short lived.
iii. Constantly replaced.
iv. Main role - increase surface for water and mineral absorption.
, 2. Cortex: several layers between the epidermis and vascular cylinder.
a. Differentiates from groun meristem - mostly parenchyma cells.
b. Endodermis: inner most layer of cortext.
i. Single row of cells surrounding the vascular tissue.
ii. Helps control mineral accumulation.
c. Casparian strip: a waxy material embedded in the transversal and radial walls of
endodermal cells.
i. Forces movement through the living cell - regulated by plasma
membrane.
ii. In some species, located in exodermis.
3. Vascular cylinder: vascular tissue that differentiates from procambium - occupies the
center of the root.
a. Differentiates from procambium.
b. Consists of primary xylem, primary phloem, and pericycle.
c. Dicots: xylem forms a central core organized in 2 or more radiating points.
Phloem is placed in between radial branches of xylem.
d. Monocots: central pith surrounded by concentric rings of xylem and phloem.
4. Pericycle: outer boundary of vascular cylinder - site for lateral root development.
Xylem and phloem:
- Similar in composition and function as with stems.
- Xylem tissue is composed of tracheids and sometimes vessel elements.
- Phloem tissue forms sieve tubes with companion cells.
- Formation:
- Protoxylem: first xylem element to mature. Capable of transporting water while
elongating - secondary walls form annual rings.
- Metaxylem: mature after cell elongation is completed. Form thick secondary
walls for water and mineral transport. Cursh protxylem cells as they grow.
- Phloem: form in area between the protoxylem arms. First part of vascular system
to become functional.
Lateral roots - role of pericycle:
1. Chemical growth regulators cause the pericycle to start dividing at specific sites
2. Resulting lateral root primordia continues to form new cells.
3. As it expands, lateral root pushes and destroys cortex cells and epidermis.
a. Endodermal cells join the newly developed root.
Secondary meristems:
1. In long-lived dicot plants, part of the pericycle cells combine with the residual
procambium (located between arcs of xylem and phloem) to produce a vascular
cambium.
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