Botany-Nonvascular Plant

Botanica

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Ministry of Education

Caribbean International School

Present by:

Subject:

Botany-Nonvascular Plant

Teacher:

Grade:

10-A

2016-2017

Introduction

Nonvascular plants are very small because their lack of a vascular system means they do not have the mechanics required for transporting food and water far distances. Another characteristic of nonvascular plants that sets them apart from vascular plants is that they lack roots. Instead of roots, nonvascular plants have rhizoids, which are small hairs that insert into the substrate to keep the plant in place. Vascular plants have roots not only for support but also to soak up water that is farther away from the plant. Nonvascular plants are commonly found in moist environments so that they are always close to a water source and can absorb the water right into the main part of the plant without relying on roots. Nonvascular plants also differ from vascular plants based on their reproductive strategies. Unlike some vascular plants that have complex reproductive strategies that include flowers and seeds, nonvascular plants have much more simple reproductive methods. Most nonvascular plants reproduce sexually by creating single-celled spores or asexually by vegetative propagation. Vegetative propagation is when part of the plant breaks off and develops into a new plant with the exact same genetic information as the original plant.

Nonvascular plants are also referred to as bryophytes and are divided into three different types, including mosses, liverworts, and hornworts. Mosses are the nonvascular plants that are most commonly seen covering the forest floor or covering the trunks of trees. Most mosses have a short central stem with wiry branches and very small leaf-like structures. These bryophytes often look soft and cushiony, or they can also resemble feathers. Mosses are the most common and diverse bryophytes and can even survive in desert environments. Some mosses can survive complete dehydration and then rehydrate when water is available again.Hornworts have thin branch-like structures and leaves that look similar to soft pine needles. These bryophytes prefer very moist environments, and some are even found submerged in ponds and lakes. Submerged hornworts can grow larger than mosses and liverworts because the water provides them with support and structure. Liverworts are often called the simplest plant. They are commonly identified by flattened leaves that often grow in two distinctive rows. Due to their flattened leaves, liverworts grow very low to the ground and form large mats over the surface. They can be found in terrestrial or semi-aquatic environments and are often referred to as weeds because they can easily take over farm land if the land is moist enough.

How are the water and nutrients transported through the plant? Explain.(5 points)

Non-Vascular plants have no true roots, leaves, or any structure with tissue, so they transport nutrients from cell to cell. In such plants almost all the cells are in contact with surrounding water; so there is not a problem of water and nutrients movement. That is why there is restriction on their height . The vascular plants have specialized tissues to do that work ( Xylem and phloem). So they can reach great heights. Mosses that have height of a centimeter or so , still show primitive conducting elements.This show the importance of conducting elements in the life of terrestrial plants. Aquatic plants have no such problem.

MountainMoss_Montage_007.jpg

In what kind of environment must a moss live in order for fertilization to take place? Explain your answer.(5 points)

It has been found in habitats ranging from the humid tropics to the polar regions, fallen logs to lakes, rivers, and streams. In fact, moss has been found just about everywhere, except in salt water. Moss is a relatively uncomplicated plant, lacking the leaves, stems, roots, and buds we often associate with “vascular plants" such as ferns, pine trees, and flowers. As a nonvascular plant, the body of moss has no roots; rather, it uses tiny threads to anchor itself to the stones, trees, or ground where it grows. The best environment for a moss to live and in order for fertilization to take place is cool,moist, and dark. Most species prefer shady ground, rock ledges, or tree trunks. Though moss prefers moist environments, it has adapted to survive periods of dry weather.

Draw a archegonium. (5 points)

Draw a antheridium. (5 points)

Describe the process by which bryophytes go from the gametophyte generation to the sporophyte generation. (5 points)

The sporophyte produces spores (hence the name), by meiosis. These meiospores develop into a gametophyte. Both the spores and the resulting gametophyte are haploid, meaning they only have one set of homologous chromosomes. The mature gametophyte produces male or female gametes (or both) by mitosis. The fusion of male and female gametes produces a diploid zygote which develops into a new sporophyte. This cycle is known as alternation of generations or alternation of phases. A multicellular gametophyte, which is haploid with n chromosomes, alternates with a multicellular sporophyte, which is diploid with 2n chromosomes, made up of n pairs. A mature sporophyte produces spores by meiosis, a process which reduces the number of chromosomes to half, from 2n to n. Because meiosis is a key step in the alternation of generations, it is likely that meiosis has a fundamental adaptive function. The nature of this function is still unresolved (see Meiosis), but the two main ideas are that meiosis is adaptive because it facilitates repair of DNA damage and/or that it generates genetic variation.