Common questions about the classes.
Having taught in introductory botany for more than five years, I have fielded many questions from students, and present below some of the more common questions and misconceptions. Thanks go to my students for taking an active role in their own education, and asking these questions
Q: Are pine trees monocots or dicots?
A: Pines are conifers, and are neither monocots nor dicots. Only flowering plants are considered to be members of these two classes. This question is similar to asking whether a chicken is a monocot or a dicot; it is neither.
Q: Do all dicots produce flowers?
A: Yes, sort of. All dicots and monocots are flowering plants, and so are descended from flower-producing plants. However, the flowers are not always large and showy the way we expect flowers to be. Oaks, maples, and sycamore are all dicot trees, but they do not produce obvious flowers. Grasses and cattails are monocots whose flowers are often overlooked because they do not have sepals or petals.
There are also some flowering plants which flower only rarely. Duckweeds are tiny flowering plants which reproduce and spread primarily by vegetative growth; they grow by cellular division, and the resulting cluster will then break apart.
Q: If monocots don't have wood, then what supports palm trees?
A: Palms rely on overlapping leaf bases, thickened enlarged cells, and prop roots to stay up. This strategy is also used by cycads and tree ferns. We hope to have a special exhibit soon expanding on the architecture of trees which will explain this in more detail.
Our objective is to study the external features of Monocot and Dicot plants.
Flowering plants, also known as Angiosperms, are the most diverse group of land plants in the world, with at least 2,60,000 living species classified into 453 families. (The word Angiosperm finds its origin from two Greek words – ‘angio’ meaning covered and ‘sperma’ meaning seed.) Angiosperms are divided into two groups- monocots and dicots.
Monocot and dicot plants have specific characteristics. We identify plants by looking at their external characteristics such as seeds, roots, leaves, flowers, pollen, stems and vascular bundles. Based on the differences, they are placed in one of these two groups.
Comparison between Monocot and Dicot Plants
There are some specific characteristics that help us identify the plant as a monocot or a dicot. Let us look at them.
Plant embryos in seeds have structures called cotyledons. A cotyledon is the central portion of a seed embryo to which the epicotyl (immature shoot) and radicle (immature root) are attached. The number of cotyledons differs in these two groups of plants and that forms the basis for the main classification of monocots and dicots. A seed of a monocot plant has one cotyledon and that of a dicot plants has two cotyledons. (Note: This is easy to remember when you know mono=one and di=two).
Roots can develop either from a main radicle that is one large taproot with many small secondary lateral roots growing out of it, or can be a fibrous mass of roots that arise from the nodes in the stem, called adventitious roots. Monocots have adventitious roots, whereas dicots have a radicle from which a root develops.
Leaves have more than one characteristic that help differentiate a monocot from a dicot. If the leaf has a stalk, then the plant is a dicot.But, in the case of a monocot plant, the leaf is sessile, which means it is attached directly by its base without a stalk.
The next characteristic that helps in the identification is the venation. If the leaves have parallel venations that are long and thin, then the plant is monocot. If the leaves have a branched venation, then the plant is a dicot.
Monocot flowers tend to have a number of petals or other floral parts that is divisible by three, usually three or six. Dicot flowers on the other hand, are likely to have parts in multiples of four or five (four, five, ten, etc.). This character is not always reliable, and is not easy to use in identification of some flowers with reduced or numerous parts.
Monocot and dicot plants have different pollen structures. In a monocot, the pollen grain produced by the flower has a single furrow or pore through the outer layer. In a dicot plant, the pollen grain has three furrows or pores.
Stem & Vascular Bundles
Monocot plants normally have a weak stem, whereas dicots have a strong stem. Vascular tissues are seen as long strands and are called vascular bundles. In the dicot plant, the vascular bundles are arranged in a ring form, whereas in a monocot, these bundles appear scattered through the stem, with more of the bundles located towards the periphery (outer edge) of the stem than at the centre.
Note: There are some exceptions to this classification however, as some species of plants belonging to monocots can have characters belonging to dicots, since the two groups have a shared ancestry.
Let's have a look on different parts of monocot and dicot plants.
- Students understand the terms angiosperm, monocot, and dicot..
- Students understand the differences between monocot and dicot plants.
- Students understand different parts of the angiospermic plant.
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