Fruit And Seed Dispersal

Seed Dispersal

Why are so many species of orchids rare, while dandelions, shepherd's purse, and other weeds occur all over the world Why are some plants confined to single continents, mountain ranges, or small niches occupying less than a hectare 2.47 acres of land The answers to these questions involve many different factors, including climate, soil, the adaptability of the plant, and its means of seed dispersal. How fruits and seeds are transported from one place to another is the subject of the following...

External Form Of A Woody Twig

Stipules Buds Bud Scales Scars

A woody twig consists of an axis with attached leaves Fig. 6.1 . If the leaves are attached to the twig alternately or in a spiral around the stem, they are said to be alternate, or alternately arranged. If the leaves are attached in pairs, they are said to be opposite, or oppositely arranged, or if they are in whorls groups of three or more , their arrangement is whorled. The area, or region not structure , of a stem where a leaf or leaves are attached is called a node, and a stem region...

Tissue Patterns In Stems

Singular Detailed Meristem Cell

Primary xylem, primary phloem, and the pith, if present, make up a central cylinder called the stele in most younger and a few older stems and roots. The simplest form of stele, called a protostele, consists of a solid core of conducting tissues in which the phloem usually surrounds the xylem. Protosteles were common in primitive seed plants that are now extinct and are also found in whisk ferns, club mosses see Chapter 21 , and other relatives of ferns. Siphonosteles, which are tubular with...

Where Are Seeds Developed In Figure 8.1

Coleorhiza

The concave side of an ordinary kidney bean a dicot has a small white scar called the hilum. The hilum marks the point at which the ovule was attached to the ovary wall. A tiny pore called the micropyle is located right next to the hilum. If this bean is placed in water for an hour or two, it may swell enough to split the seed coat. Once the seed coat is removed, the two halves, called cotyledons, can be distinguished Fig. 8.28 . The cotyledons, which have a tiny immature plantlet along one...

Asexual Plant Propagation

Plant Propagation Crown Division

In recent years, we have heard amazing stories about scientists who have cloned animals such as sheep and cows. Botanists are far ahead in that arena. They have been cloning plants for centuries Many plants are easy to propagate asexually, using vegetative parts rather than seeds. For example, crown division is a simple technique in which a plant is separated into several pieces, each of which contains a crown and a portion of the root system Fig. 14.17 . This is commonly used for many...

Apomixis and Parthenocarpy

Some embryos of seeds can develop apomictically that is, without development or fusion of gametes sex cells but with the normal structures e.g., ovaries otherwise being involved. An embryo may develop, for example, from a 2n nutritive cell or other diploid cell of an ovule, instead of from a zygote. After germination, this makes the plant that develops from such a seed the equivalent of a vegetatively propagated plant. Fruits that develop from ovaries having unfertilized eggs are said to be...