When doing biology problems, how to distinguish between monocotyledons and dicots

In all angiosperms.

, it can be divided into two major categories, namely dicots.

and monocots. The fundamental difference between them is the development of two ** leaves or one ** leaf in the embryo of the seed, two are called dicots, and one is called monocots. The former are such as apples and soybeans; The latter are like rice, corn.

These two types of plants are relatively easy to distinguish because there are some distinct morphological differences between them. The root system of dicots, which is basically straight.

The taproot is well developed; Many are woody plants, and the stems can be thickened; The leaf veins are reticulated; The number of sepals and petals in the flower is 5 or 4, and if the petals are combined, there are 5 or 4 lobes. The root system of monocots is basically fibrous root system, and the taproot is underdeveloped; Mainly herbaceous plants.

There are few woody plants, and the stems usually do not thicken from year to year; The leaf veins are parallel veins, and the number of sepals and petals in the flower is usually 3, or a multiple of 3. The above differences make it easier to distinguish between monocots and dicots.

Monocot cotyledons monolithic, also known as shields, have endosperm; Dicotyledonous plants, cotyledons with two cotyledons, and the endosperm is absorbed during embryonic development, so there is no endosperm! This is the knowledge of the first semester of the first semester of junior high school, according to what our biology teacher said. Monocotyledon nutrition is mainly in the endosperm and dicot nutrition is mainly in midnight.

In a general sense, monocots are striped leaves, parallel veins, flowers three - six cardinal bases, such as: wheat, corn, junzi orchid, narcissus, aloe vera and so on! Dicotyledons are all reticulated leaf veins with four-five cardinal flowers, such as tomatoes, watermelons, poplars, willows, peaches, etc.

There are exceptions, but there are very few, and if you judge it like this, it's usually right!

If you can't remember, think about whether the plant seed can be broken in half by hand like peanut seeds, and the germ is sandwiched between the two ** leaves, if it can be a dicot, it can't be a monocotyledon.

Most of the plants are flowering plants, that is, angiosperms. There are about 250,000 species of flowering plants in the world, which is very diverse. Flowering plants can also be divided into monocots and dicots according to the number of cotyledons, monocots have only one leaf, and dicots have two leaves.

Differences:1Pulse sequence of the leaf.

The leaf veins of monocots are mainly reticulated veins, that is, the leaf veins are arranged in a reticular pattern. The leaf veins of monocots are mostly parallel and arcuate.

2.The type of root system.

Most dicots have well-developed taproots, so dicots mostly have straight roots. The taproot of monocots is less developed and obvious, so monocots mostly have fibrous roots.

3.The morphological structure of the flower.

Dicotyledons generally have 4 or 5 flower bases, and the calyx and corolla are not very similar in shape; Monocots generally have 3 flower bases (some 2 and 4, and a few flower bases are also 4 or 5), and the calyx and corolla are relatively similar.

4.Other. There are many other differences in the anatomy between monocots and dicots, such as:

a.Dicotyledons are not closed at the end of the branch, so there are free branch terminals.

b.Stomata on dicot leaves, irregularly arranged.

Based on the above, we can basically determine whether an angiosperm belongs to the class of monocots or dicots.

Although there are many differences between the two, there is also a connection between the two. Both are taxonomically belonging to the phylum Angiosperms and are the main constituent parts of angiosperms. In addition, scientists generally believe that monocots evolved from the ancestors of extinct dicots, such as cateols and water lilies.

I'll just talk about it briefly.

Differences:1Cotyledon.

The seed embryo of monocots has a ** leaf in it; Dicotyledons are two.

2.Vascular bundles.

The vascular bundles of monocots are scattered; Dicotyledons are ring-ordered.

3.Root. The root system of monocots is a virtual root system, and the taproot is underdeveloped and formed by adventitious roots. Dicotyledons have a straight root system with well-developed taproots.

4.Number of petals.

The base number of monocots is 3;

Dicotyledons are 4 or 5.

5.Leaf vein order.

Monocot veins are parallel or arcuate; Dicotyledons are reticulated vein-ordered.

These distinctions are enough for high school memorization, and there are common monocots: wheat, rice, and bamboo. Dicotyledons: peanuts, soybeans, sunflowers.

I can't remember the similarities, so I can find them from the differences. For example, there are roots, seeds, flowers, vascular bundles, chloroplasts, photosynthesis, all angiosperms.

Hope it works for you.

1。Leaf veins: monocotyledons are parallel veins, and dicotyledons are mostly reticulated veins.

2。Epidermal cells: The epidermal cells of monocots are rectangular in regular arrangement. The epidermal cells of dicots are irregularly shaped.

3。Stomata: The monocotyledon guard cells are dumbbell-shaped, with paraguard cells. The dicot guard cells are kidney-shaped, and there are no paraguard cells.

4。Mesophyll: The mesophyll cells of dicots are divided into palisade tissue and spongy tissue, while monocots do not.

5。Vascular sheath: Monocot leaves have vascular sheaths, while dicots do not.

If you look at it with the naked eye, the characteristics of the veins are best distinguished. When the cross-section of the leaf is observed under the microscope, it is generally determined by the presence or absence of palisade tissue in the mesophyll cells and the presence or absence of vascular bundles around the ducts.

Similarities: Both are angiosperms. Angiosperms have real flowers, so they are also called flowering plants; The ovules are well protected by the ovary encapsulated in the ovary, and the fruit formed by the ovary after fertilization both protects the seed and helps the seed to spread in various ways; The endosperm with double fertilization and triploid is not a simple female gametophyte, but has the characteristics of both parents, so that the new plant body has stronger vitality; Sporophytes are highly developed and further differentiated, and are more herbaceous except for trees and shrubs; In terms of anatomical structure, there are ducts in the xylem, sieve tubes and companion cells in the phloem, which make the conduction tissue structure and physiological function more perfect, and at the same time, in terms of chemical composition, with the evolution of angiosperms and continuous development and complexity, angiosperms contain all the types of natural compounds and have a variety of physiological activities.

Angiosperms are divided into two categories: monocots and dicots, and there are differences in the number of cotyledons, the number of petals, and vegetative organs, and the most important difference is the number of cotyledons.

Number of cotyledons. The embryo of monocot seeds has one leaf, such as corn, wheat, rice, etc.; The embryo of dicot seeds has two ** leaves, such as beans, peanuts, broad beans, soybeans, etc.

The number of petals. The former is usually 3 and the latter is 5 or 4.

vegetative organs. Dicotyledons have well-developed taproots, vascular bundles in the stems are arranged in a ring, and the leaf veins are mostly reticulated; Monocots have well-developed fibrous roots, the taproot is underdeveloped, the vascular bundles in the stem are often scattered, and the leaf veins are mostly parallel or arcing.

The above distinction is not absolute, and there are some exceptions. For example, monocotyledons are also found in the water lily family in dicots, and liliaceae in monocots also have 4 cardinal flower types.

Problem solving process] is the same point as the characteristics of the whole angiosperm.

Monocots:

Seeds: 1**leaf.

Leaf veins: parallel veins.

Roots: Generally, the taproot is underdeveloped, and the fibrous root system is formed by most adventitious roots.

Flowers: The number of flowers is usually 3, and the calyx and corolla are very similar.

Dicotyledons:

Seeds: 2** leaves.

Leaf veins: reticular veins.

Roots: Generally, the taproot is well developed, so it is mostly a straight root system.

Flowers: Plants usually have a flower base of 5 or 4, and the morphology of the calyx and corolla is also very different.

Seedless plants include ferns, bryophytes, bathing plants.

Dicotyledons have two **leaves.

3. It can be in a low-temperature, dry environment, and pay attention to ventilation, if possible, nitrogen, helium, and other rare gases can be introduced to reduce the concentration of oxygen and reduce aerobic respiration.

From the point of view of seeds, monocotyledons have both embryonic structure, and their main difference is that the cotyledons of monocots belong to the structure of transporting nutrients, auxiliary nutrition, and their main vegetative tissue is endosperm, while dicots have two cotyledons, no endosperm, and cotyledons play a nutritional role. The endosperm of monocotyledons is developed by fertilized nodules in flowers, while dicotyledons consume fertilized nodules when seeds are formed.

The monocotyledonous leaves are parallel veins like coconut palms, while the dicots are reticulated, like apple trees.

Monocots tend to have eccentric inflorescences, while dicots are more regular.

The branch ends of dicots are not closed, so there are free branch terminals; In monocots, the branch ends are closed, so there are no free branch endings. The embryo of dicot seeds usually has two leaves, such as soybean, peanut, pumpkin, etc.; The embryo of monocot seeds has only one ** leaf, such as rice, onion, corn, etc. The vascular bundles in the stems of dicots are arranged in a ring, that is, arranged in a circle, and there is a cambium layer, which can produce secondary xylem and secondary phloem, which belongs to infinite vascular bundles (open vascular bundles), so the stems of dicots can continue to thicken; Whereas, the vascular bundles in the stems of monocots are scattered and not arranged in loops.

If it is arranged in a circle, it is arranged in two or more circles, and there is no cambium, so it cannot produce secondary xylem and secondary phloem, and it is a finite vascular bundle (closed vascular bundle), so the stem of monocots cannot be arbitrarily thickened. The stomata on the leaves of dicots are irregularly arranged, and most of them are scattered, such as geraniums, cotton, etc.; The stomata on the leaves of monocots are arranged in a relatively regular manner, mostly arranged in rows, such as corn. The pollen of dicots has 3 germination pores, such as rape; Pollen from monocots often has a single germination pore, such as corn.

Resources.

Except for a few people upstairs, the leaf veins of monocots are generally parallel, and the dicotyledons are reticulated veins; The monocotyledons are generally three, and the dicotyledones are four or five; In addition, monocots are generally annual or perennial herbaceous, and dicot species are mostly woody (some are herbaceous).

Monocots and dicots can usually be seen from the seeds, and in monocots such as wheat and corn, the seeds cannot be divided into two halves. The seeds of dicots can be easily split into two halves, such as peanuts. Then it is distinguished from the buds, which usually have two leaves.

If you can't judge yet. It needs to see if there is endosperm after the embryo develops, and the endosperm will disappear completely after the development of this dicot plant, while the monocotyledons will remain.

One of the embryonic cotyledons grows up to be monocots, and the other is dicots.