PBS 101.23 Morphology of Stems

Questions and Answers

What is the main characteristic of stems that enables them to grow towards light?

Thermotropism

Hydrotropism

Phototropism (correct)

Geotropism

Which part of the plant develops into the stem?

Radicle

Cotyledon

Root

Plumule (correct)

What type of stem is characterized by a thin and elongated structure that cannot stand erect?

Woody stems

Prostrate stems

Herbaceous stems

Creepers (correct)

Which type of stem modifies itself for storage of food?

All stem types Signup and view all the answers

In a twig, what do you call the region of the stem where leaves are attached?

Node Signup and view all the answers

Which of the following stem modifications supports climbing?

Tendrils Signup and view all the answers

What is the term for stems that are capable of conducting water and minerals?

Vascular stems Signup and view all the answers

Which arrangement of leaves is described when they are attached in pairs on the stem?

Opposite arrangement Signup and view all the answers

What is the primary function of prickles in plants?

For protection Signup and view all the answers

Which plant is an example of having terminal buds that develop into tendrils?

Passiflora Signup and view all the answers

Which of the following stems is primarily used as a source of sucrose?

Sugarcane Signup and view all the answers

What are bulbils primarily used for in plants?

Vegetative propagation Signup and view all the answers

Which of these plants is commonly used for industrial fibers sourced from its stem?

Jute Signup and view all the answers

Which of the following is not a culinary use of underground stems?

Rice Signup and view all the answers

Which plant produces latex that is used in rubber production?

Hevea brasiliensis Signup and view all the answers

What is the main purpose of stems producing gums in certain plants?

Injury healing Signup and view all the answers

What is the term used to describe the xylem produced in spring that has relatively large vessel elements?

Spring wood Signup and view all the answers

How does the size of vessel elements change during the growing season in a broadleaf tree?

They become progressively smaller. Signup and view all the answers

What does an annual ring in a tree represent?

One year’s growth of xylem Signup and view all the answers

Which of the following factors can contribute to a narrower annual ring?

Caterpillars stripping the leaves Signup and view all the answers

What type of wood predominates in conifers compared to broadleaf trees?

Tracheids Signup and view all the answers

What tool can be used to determine the age of a woody plant without cutting it down?

An increment borer Signup and view all the answers

What indicates that a year had higher than normal growth conditions in a tree's life?

A wider annual ring Signup and view all the answers

What evidence might you find next to an annual ring to indicate a past fire event?

Burn scars Signup and view all the answers

What is the primary characteristic of siphonosteles found in ferns?

They have pith in the center. Signup and view all the answers

In which type of plants are eusteles predominantly found?

Present-day flowering plants and conifers Signup and view all the answers

What type of vascular bundles do herbaceous dicotyledonous stems primarily have?

Discreet patches of xylem and phloem Signup and view all the answers

Which statement accurately describes the cambium in herbaceous dicot stems?

It produces both primary and secondary vascular tissues. Signup and view all the answers

How do woody dicotyledonous stems differ from herbaceous dicots as they mature?

They develop secondary tissues from cambium. Signup and view all the answers

What feature distinguishes the wood in tropical trees from that in temperate trees?

Tropical trees produce uniform wood year-round. Signup and view all the answers

What happens to the growth patterns of woody plants in temperate climates?

Spring and summer are their growth seasons. Signup and view all the answers

What role does the procambium play in vascular development?

It produces primary xylem and phloem. Signup and view all the answers

What is the primary function of resin produced by resin canals?

To deter insect attacks and prevent fungal development Signup and view all the answers

How long do the fascicles of bristlecone pines typically persist?

Up to 30 years Signup and view all the answers

Which tissue is referred to as bark?

All tissues outside the vascular cambium Signup and view all the answers

What happens to older layers of phloem over time?

They become crushed and functionless Signup and view all the answers

What do the sieve tubes in younger layers of phloem primarily transport?

Sugars and other substances Signup and view all the answers

What are laticifers in plants known for?

Secreting latex Signup and view all the answers

Which statement is true about the parenchyma cells of the cortex?

They become crushed or sloughed off over time. Signup and view all the answers

Which plant cells commonly contain multiple nuclei?

Laticifers Signup and view all the answers

Study Notes

General Structure of Stems

Stems develop from the plumule and are the aerial part of the plant.
Composed of axis, nodes, internodes, and buds.
Types include aerial, sub-aerial, and underground stems.
Mechanical tissue presence classifies stems as weak (creepers, climbers, twinners), herbaceous, or woody.
Functions include supporting leaves for photosynthesis, conducting water and nutrients, and producing flowers and fruits.

External Structure of Stems

Woody twigs consist of an axis with attached leaves.
Leaf arrangements can be alternate, opposite, or whorled.
Nodes are where leaves attach; internodes are the segments between nodes.
Stem types include siphonosteles (common in ferns) and eusteles (discrete vascular bundles as seen in flowering plants).

Herbaceous Dicotyledonous Stems

Characterized by green, nonwoody stems, typically in annual plants.
Vascular bundles contain patches of xylem and phloem formed in a cylindrical arrangement.
Procambium initially produces only primary xylem and phloem; later, vascular cambium develops for secondary growth.

Woody Dicotyledonous Stems

Young stems show similar arrangements in primary tissues before differences emerge with the vascular cambium and cork cambium.
Secondary xylem (wood) develops seasonally, creating annual growth rings.
Spring wood features large vessel elements; summer wood has smaller elements and more tracheids.
Annual rings indicate tree age and reflect environmental conditions experienced during growth.

Stem Modifications

Prickles and thorns develop from outer stem tissues for protection.
Stem tendrils, such as those in vines, provide structural support.
Bulbils modify floral buds for vegetative propagation, as seen in Dioscorea and Agave.

Uses of Stems

Underground stems can serve as food (e.g., potato, garlic) or spices (e.g., ginger).
Stems like jowar and rice are valuable as fodder.
Industrial fibers are sourced from jute, hemp, and flax.
Sugarcane stems are harvested for sucrose; latex from certain stems, like rubber trees, is used commercially.
Wood from various plants serves medicinal purposes (e.g., quassia, sandalwood).
Gums from injured stems are utilized in various industries (e.g., gum-acacia).

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Description

Explore the detailed morphology of stems in this quiz based on PBS 101.23. Topics include the general, external, and internal structures of stems, as well as stem modifications and their uses. Enhance your understanding of plant anatomy with these key concepts.