Topic: Stem

Author: Elżbieta Szedzianis

Target group

Students of the 5th grade of an elementary school.

Core curriculum

5 ) Flowering plants. Student:

b) observes the flowering plant (photographs, engravings, live specimens); recognizes its organs and determines their functions (root, stem, leaf, flower),

c) describes modifications of roots, stems and leaves as adaptation of angiosperms to life in specific environments,

d) presents methods of vegetative reproduction of plants and observes selected methods of vegetative reproduction.

The general aim of education

The students describe the structure and adaptation of stems to perform life functions.

Criteria of success

• You will give three characteristics of the stem structure that enable it to perform vital functions,

• describe the experiment that shows the movement of water in the stem,

• name two tissues in which the transport of water and sugars takes place.

Key competences

• communication in foreign languages;

• communication in the mother tongue;

• mathematical competence and basic competences in science and technology; 

• learning to learn.

Methods / techniques

Outdistance strategy; direct observation, work with film, conversation, workshop - solving tasks.

Individual work.

Teaching aids

• abstract;

• interactive or traditional board;

• tablets/computers;

• geraniums or other flowering pot plants.

Lesson plan overview (Process)

Note, the „Stem” topic is realized after the „Leaf” topic.
The homework before this lesson consisted in watching the film from the Internet titled „Colored flowers | Color changing flower experiment | Science experiments for kids | Elearnin” (first 3 minutes) and answering the following questions:
What function of the stem was shown in the film?
Where from and where to does water in the stem?
Why does water go from the root through the stem to the leaves and fruit?

Introduction

1. The teacher displays the 1st paragraph of the abstract with the accompanying illustration: What do a blade of grass, a redwood tree, a bulb of potato and a black locust thorn have in common? They are all stems that took forms that were best suited to survival, as a result of adaptation to the environment.
   The teacher asks the students to point the keyword and say in their own words what these two sentences are about. The teacher asks the students to indicate stems in the illustration.

2. The teacher gives the topic, the goals of the lesson in a language understandable for the student, and the criteria of success.

3. The teacher reminds the homework and asks selected students to read it.

Realization

1. The teacher asks the students to re‑watch the film indicated in the homework without sound and write a commentary to it. The students will work in groups of 2‑3 people, each of which has access to a computer/tablet. The students watch the selected parts of the film and perform the tasks:
   0.20‑0.25 - formulate a question - the title of the film,
   0.30‑0.39 - list what is needed for the experiment,
   0.45‑1.40 - describe how the experiment was carried out,
   2.11‑3.00 - explain how and why the dye moved through the stem to the flowers.

2. The students from two groups present the commentaries to the film. The teacher asks - “How to check if the dye has also reached rose leaves?”. The teacher asks for an explanation of how this happened.

3. The teacher gives pot plants to the groups, e.g. flowering geraniums. The teacher asks the students to orally describe the external structure of the stems. Then, they supplement the sentence Adaptation of the stem to perform life functions written on the board with functions related to the plant structure features identified during the observation of the plant and the film (green, stiff, branched, containing vascular tissue).

4. The teacher displays the graphic entitled „Transport of sugars in the stem”. The teacher explains that the stem transports sugars from the leaves to the remaining organs through phloem cells.

Summary

1. The teacher asks the students to perform interactive task No. 1.
   The teacher explains that the students have to formulate answers in various ways to find the answer predicted by the author.

2. The teacher asks the students to explain why the stem transports water to the leaves, and sugars to fruits, flowers and roots.

Homework for keen students.

Do interactive exercises 2 and 3.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Stem

The stem is an element of the shoot, above‑ground organ of the vascular plant. It combines roots with leaves, flowers and fruits. The stems transport water and mineral salts collected by the roots and organic compounds produced in the leaves during photosynthesis. These substances reach all parts of the plant via the conducting tissues located in the stem and its branches. The stem keeps leaves, flowers and fruits in the right position. The leaves on the stems are arranged in such a way as to absorb as much light as possible. Flowers and fruits are often formed on the tops of the stems. Thanks to this, pollen and mature seeds of plants pollinated and spread by the wind can be transferred to larger distances than if they were produced close to the ground. In many of the angiosperm plants, the stem is used for asexual (vegetative) reproduction. This means that (in appropriate conditions) its fragment can produce roots and transform into an independent plant. The stems also act as storage organs. Plants of various species accumulate in them nutrients or water, enabling survival in difficult conditions.

Stems can take many forms, from powerful tree trunks, through thin stems of vines, to underground tubers. This is due to the diversity of conditions in which plants live and the length of their lives. Regardless of the shape and function of the stem, we find nodes, internodes and buds. At the top of the stem there is an apical bud, in which a shoot apical meristem is hidden by the budding leaves. Thanks to the meristematic tissue present in it, the plant grows to length. Below the apical bud from axils grow the axillary buds (named also lateral buds). They may contain initials of flowers (flower buds) or shoots (shoot buds). As it grows the main shoot from the flower buds develop flowers and from the shoot buds, shoot branches. Leaf buds which contain leaf initials produce leaf. The bud seating areas are called nodes. Leafless sections between them are internodes. The number and length of internodes determines the height of the plant.

The great variety of stem and stem structure in seed plants results from the various functions that these organs perform. Due to the structure and durability of the stems, herbaceous stems and woody stems are distinguished.

Herbaceous stem are delicate and flaccid, as they contain little supporting tissues. Under their thin woody stem there is parenchyma with chloroplasts giving them a green color. These stems grow mainly in length, their growth in thickness is insignificant. They are unstable and die for the winter. We meet them in many plants, such as poppy field, wheat, bean, astra, daisy.

Trees and shrubs have woody stems. Thanks to the secondary increase in thickness from year to year, these stems increase their circumference and take the form of massive stems. They have strongly developed wood - the vascular part of the conducting tissue. From the outside they are covered with a cork forming a bark. Such a construction ensures plants longevity and resistance to adverse environmental conditions.

Plants most often have raised stems that rise straight up. They are allowed by the presence of reinforcing tissue and wood elements of the conductive tissue. Some plants produce slender and long stalks that crawl on the ground. Stalk - mainly refers to elongated stems, e.g. grass blades (grass‑stalk). It is used to describe the stalk that attaches the leaf blade to the stem (leafstalk, petiole) and fragments of the stalk that support flowers (flower stalk, pedicel). From such stems, apart from the leaves, the adventitious roots may also grow, which the plant attaches to the substrate. Other plants have winding stems that climb towards the light, wrapping around the supports or attaching themselves to them with the help of tendrils or pulvillus.

Stems, and often whole shoots, can have unusual shapes. This is the result of adaptation to perform different functions depending on the conditions of the environment in which they live.

Modified stems are, for example:

• tubers, strongly shortened and thickened underground shoots, filled mainly with granula parenchyma tissue; they are also used for asexual reproduction; on the tubers there are buds from which aerial shoots grow under favorable conditions; tuber producing plants include perennials: potato, Jerusalem artichokes;

• runners, elongated stems of plants creeping on the earth's surface; after the stem plant has died or separated from it, it becomes an independent plant; the main function of runners is therefore asexual reproduction; examples of plants that produce runners are: strawberries, wild strawberries, root bugling;

• thorny shoots, short, sharp tips and strongly ligaments that are side shoots of the plant; have their own conductive beam that connects them to the main shoot - for this reason it is difficult to break them off the plant; thorns protect plants from being eaten by herbivorous animals, they are characteristic of plants inhabiting typically dry environments, they occur in sloe, locust;

• shoot whiskers, stems on which residual leaves and flowers may occur; these thin and flaccid clinging organs, which, when touched, wrap around the support, are found, for example, in vines.

• cladods, green, flat stems of hygrophobes, which have taken assimilation functions, because their leaves have disappeared or have been reduced, in cacti, e.g. opuntia, the stems have become like leaves, and these have turned into thorns, the green stem plays a double role: runs photosynthesis and collects water in the parenchyma aquifer.

• The stem and the leaves form the above‑ground part of the plant called the shoot.

• The stem holds the leaves, flowers and fruits, and it is responsible for the transport of substances and asexual reproduction. It can also have storage and assimilation functions.

• Differences in the structure of plant stems are related to the functions performed by these organs.