Biology Homework Chapter 31: Plant Structures
Textbook assignment: Chapter 31: Plant Structure, Reproduction, and Development, sections 1-8.
- 31.1 Humans live in symbiosis with most food-source plants: humans provide idealized growing conditions with fertilizers, irrigation, and breeding programs that have produced high-yield hybrids and cultivars, plants provide food and replenish atmospheric oxygen.
- 31.2 Plant structures fall into two groups: monocots (linear veins, one seed leaf, scattered vascular bundles, 3-petal flowers), and dicots (netted veins, two seed leaves, compact bundles, floral parts in multiples of 4 or 5).
- 31.3 Roots anchor the plant and absorb water and nutrients from the soil; shoots (stems, leaves, flowers) are where photosynthesis occurs.
- 31.4 All plants have roots and shoots although the form of these structures shows a wide range of adaptations to particular environments. These can also be grouped as root, stem, and leaf systems when the focus is on tissue variation.
- 31.5 By tissues type, we get three systems:
- The epidermis, a single layer of cells providing protection from disease and infection; this layer may be covered with a waxy cuticle.
- The vascular tissue system composed of the xylem and phloem
- The ground tissue system which is everything else, including leaves with their guard cells controlling the size of the stomata, and the mesophyll layers of leaves where gas exchange and photosynthesis occur.
By structure, we get three systems (leaf, stem, root), which have different forms in eudicots and monocots:
- Leaves: net-veined vs straight-veined
- Stems: vascular bundles around rim vs bundles distributed throughout
- Roots: Thick cortex, narrow vascular cylinder vs thinner cortex, wide cylinder
- 31.6 Plant cells vary, but most use multiple layers of cell walls for structure, and contain chloroplasts but lack lysosomes, in contrast to animal cells. The major types are:
- parenchyma cells (primary walls, store food, support photosynthesis).
- collenchyma cells (thick primary walls, provide support)
- sclerenchyma cells (rigid secondary walls, support and protect plant interior)
- water-conducting cells (tracheids and vessel elements forming xylem tissue)
- food-conduct cells (sieve plates, companion cells forming phloem tissue)
- 31.7 Plants grow throughout their lives, which may last one year (annuals), two years (biennials) or more (perennials). Primary growth lengthens roots and shoots and occurs primarily in the meristems, either at the tip of the plant shoots or roots (apical meristems) or in auxiliary buds at branch points.
- 31.8 Secondary growth increases the girth of woody plants at the vascular cambrium layer beneath the bark. Inside this layer, the tissues die, forming heartwood. Those which still carry phloem are sapwood.
Read the following weblecture before chat: Plant Structures.
Take notes on any questions you have, and be prepared to discuss the lecture in chat.
Perform the study activity below:
Use the virtual plant dissections at VR Plants to explore plant tissues in different regions of the pant.
Chat Preparation Activities
- Essay question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
- Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.
- No quiz yet: the Chapter Quiz opens when we finish the chapter.
Read through the lab for this week; bring questions to chat on any aspect of the lab, whether you intend not perform it or not. If you decide to perform the lab, be sure to submit your report by the posted due date.
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