Source: Experiments in Botany
Operation method
basic program
Principle
There are hundreds of thousands of species of plants living on Earth, each with its own morphological characteristics. The morphology of the same plant may vary to different extents due to both genetic and environmental influences, and each plant may be different. Even the organs (e.g., leaves and stems) on the same plant may vary greatly when they are in different parts of the plant. This is the diversity of plant forms. However, there are always morphological similarities or identities within the same group, while morphological differences can always be found between plants of different groups, and in the case of the plant kingdom as a whole, from algae to angiosperms, there has been a great evolution in morphology due to their different positions in the evolutionary history. Since angiosperms are the most highly evolved taxa in the plant kingdom and have the largest number of species, the study of plant morphology, structure, phylogeny and ecology is more often confronted with angiosperms.
Materials and Instruments
Plants Move 1 Observation of plant life type The life type of a plant is the type of outward appearance developed by the plant as a result of long-term adaptation to integrated environmental conditions. Observe plants and distinguish between trees, shrubs, herbs and vines. The stems of native plants are more lignified and the above-ground parts do not die, while the opposite is true for herbaceous plants. To distinguish between trees and shrubs, we need to examine whether the adult plant has a clear trunk: those with a clear trunk are trees, such as aspen, willow, etc., while those without a clear trunk are shrubs, such as moonflower. Woody plants are also evergreen and deciduous: deciduous trees or shrubs in the winter leaves, such as peach; and evergreen plants in any season of the year on the branches have green leaves, such as pines. In herbaceous plants, those that complete their life history in one year and then die are annual herbs, such as fava beans; those that undergo nutritive growth in the first year, flower and fruit in the second year and then die are biennial herbs, such as cabbages; and those that live for many years in a row, flower and fruit above ground and then die every winter, while the underground part of the plant survives are perennial herbs, such as iris. Vines can also be divided into two categories: one for essential vines, such as grapes; the other for herbaceous vines, such as petunias . Observations and Reflections: ① Do evergreen cypresses lose their leaves? Why do they still have green leaves in winter? ② Are trees always taller than shrubs? Do shrubs become trees when they grow up? 2 Observations on the Morphology of Plant Nutrient Organs (1) Roots and root systems Roots are the part of the plant that grows downward, absorbs water and minerals, and acts as a cement and support. The part that grows underground is not necessarily the root of the plant. Some are metamorphic stems, such as the tuber of potato, bulb of cucumber, bulb of garlic and rhizome of fern. And some plants have small fixed roots that are not buried in the soil, such as the adventitious roots that arise from the nodes of near-ground stems of corn that act as mechanical supports. A plant's roots of the general term that the root system pull up the root system of a dicotyledonous herb, it can be seen that it has a clear main root, this is the taproot system and then pull up the root system of a single in the leafy cypress, it can be seen that there are many fibrous roots, there is no obvious main root, this is the fibrous root system. Observations and Reflections ① underground part of the plant, how to know whether it is a root or a stem? (2) What are the advantages of the taproot system and the fibrous root system for the function of absorbing water and minerals? (2) Branches and Shoots The stem of a plant and the structures such as leaves, flowers and buds attached to it are collectively called branches. Observe the branches of a woody plant: the position of the leaves is called a node, the section of the stem between two nodes is called an internode, and the marks left after the leaves have fallen off are called leaf scars. There are various ways of plant branching, common in seed plants are: uniaxial branching, such as cypress, poplar; uniaxial branching, such as apples; pseudo-bifurcated branching, such as lilac, buds are attached to the stem of the wood spreading branches, flowers or inflorescences of the prototype, according to its position can be divided into terminal buds and lateral buds, according to its nature can be divided into branch buds, buds, buds, or a mixture of buds. The terminal and lateral buds of branch ten of plants such as magnolia are peeled off with forceps to determine the nature of these buds. (3) Leaf sequence and leaf type Leaf sequence refers to the arrangement of leaves on a branch. When one leaf is borne on each node, it is alternate, when two leaves are borne opposite to each other, it is opposite, when three or more leaves are arranged in a round, it is whorled, and when two or more leaves are borne on one side of a node, it is clustered. Compare and contrast the arrangement of plant leaves to determine the type of leaf sequence. A complete leaf is divided into three parts-the blade, the petiole, and the stipules. The stipule is a lamellar structure at the base of the petiole; not all plant leaves have stipules. Observe the leaves of various plants and determine which plants have stipules and which do not. Note that some plants lose their stipules early, so look carefully at the base of the petiole for signs that the stipules have fallen off. If there is only one leaf on a petiole, it is a simple leaf; if there are more than one leaf on a petiole, it is a compound leaf. Compound leaves are divided into palmately compound leaves and pinnately compound leaves, pinnately compound leaves are further subdivided into odd pinnately compound leaves and even pinnately compound leaves, as long as there are terminal leaflets can be recognized as odd pinnately compound leaves. In addition, some plants have branched petioles first, Ran in the branching said hooked into compound leaves, which may be two or even more compound leaves. Observe the leaves of each plant to determine their type, and then describe them in terms of their shape and the characteristics of their tips, bases, and margins. Observations and Reflections ① If the single leaves on the twigs of a particular plant are arranged in a plane, how can they be distinguished from pinnately compound leaves? ② What is the pattern in the spatial distribution of leaves? What is the significance of the mosaic arrangement of leaves? 3 Observations on the morphology of plant reproductive organs (1) Flowers and Inflorescences Flowers are highly shortened branches adapted for reproductive functions A complete flower should consist of a pedicel, receptacle, calyx, corolla stamen group and pistil group. The morphology of flowers varies greatly among different groups of plants, whereas the morphology of the same group of plants always has relatively stable features. The structure of flowers is the most important morphological basis for the classification of angiosperms. For an angiosperm, its symmetry (bilateral/radial), the number and arrangement of flower parts (sepals, petals, stamens, pistils), and whether they are free or connate should be examined. Dissect the flower longitudinally and determine whether the ovary is fused to the receptacle or calyx tube; if the ovary is not fused to the other parts, it is superior, otherwise it is inferior or semi-inferior. The flowers of some plants are borne singly on the tops of branches, as in the case of the magnolia; or singly in the axils of the leaves. And the flowers of most plants form various types of inflorescences. Observe the various types of inflorescences, such as the spikes of plantain, the glory-cut inflorescences formed by poplars such as woolly poplar, the fleshy spikes of calla lily, the racemes of shepherd's purse, the heads of dandelion, the umbels of leeks, the compound umbels of carrots, the corymbs of daffodils, and the cymes of stonecrops, and so on. (2) Fruits and seeds The fruit is a structure that develops from the ovary part of the fertilized pistil in a flower. But sometimes the fruit is not formed purely from the ovary of a flower. Observe the cymose fruit of the mulberry and note that it is formed from an inflorescence. Each polyanthus contains multiple fruits formed from multiple flowers. In contrast, the fruit of magnolia, for example, is a polymerized fruit, which contains multiple small follicles, but each polymerized fruit comes from a single flower containing multiple free pistils. If a flower containing a single pistil forms four fruits, this is a single fruit. In some groups of plants the formation of single fruits involves parts other than the ovary; such fruits are pseudofruits, and only fruits formed purely from the ovary are true fruits. Achenes of dandelions, sunflowers, and other plants of the Asteraceae family are formed from the inferior ovary and are thus pseudofruits. The pericarp of the fruit can be divided into three layers: exocarp, mesocarp and endocarp. The texture of the three layers of pericarp varies among different types of fruits, and the fruits observed during dissection are judged according to the texture of the pericarp of each layer of the fruit, whether it dries out after ripening, and whether the ovary chamber is open or not to determine whether the fruits are classified as scraped. Nudibranchs have only seeds, not fruits. Observe the pine plant such as oil pine "ball fruit", it has a number of pieces of seed scales arranged in a spiral, break a scale, visible at the base of a pair of winged seeds, seed scales and the composition of angiosperms similar to the gynoecium of the cortex, but it is not through the edge of the healing of the seeds tightly encapsulated. The seeds of angiosperms are located in the fruit, and the fruit under observation was peeled back to observe the number and morphology of the seeds within it. 4 Examination of Plant Morphological Variation The plant kingdom is characterized by a wide variety of species and forms. Each type of plant has a different degree of variation in its morphological traits. Observe the various plants growing in the campus and note the morphological variation between plants and within the same plant species to grasp the following points. (1) Variation is common in the plant kingdom, change is absolute and invariance is relative, note which traits are highly variable and which are relatively stable, and pay attention to examining the magnitude of variation. (2) There are both similarities and differences in morphology between individual plants and individuals, and between taxa and taxa. Note which features are individual and which are common. (3) For a given plant, there are features that distinguish it from other plants, but some features are essential and others are non-essential. Be careful to examine those essential features. For more product details, please visit Aladdin Scientific website.
Hand-held magnifying glass, tweezers, tape measure, etc.