Morphology of Angiosperms - 2

As the cells reach their maximum length, many epidermal cells develop lateral protrusions called root hairs. These serve to increase surface area for better absorption.

Seed coat dormancy is observed when the seed coat is impermeable to water, and gases (oxygen). It requires action by weathering, microorganisms, passage through an animal's digestive track, or fire to soften the seed coat.

Dormancy that is caused by an impermeable seed coat is known as physical dormancy. Physical dormancy is the result of impermeable layer(s) that develops during maturation and drying of the seed or fruit. This impermeable layer prevents the seed from taking up water or gases. As a result, the seed is prevented from germinating until dormancy is broken.

Each microsporangium is lined with a nutritive tissue layer called the tapetum and initially contains diploid pollen mother cells.

Central placentation is also known as free placentation. Here, the placentae are arranged in a central column within a non-sectioned ovary and is seen in compound carpel.

In open aestivation the petals or sepals do not overlap or even touch each other. Example: Corolla in Brassica.

Compound umbel is where the peduncle is branched from the tip of each branch a luster of flowers is produced in an umbellate manner called a compound umbel. Example: Coriander, carrot.

A samara is a winged achene, a type of fruit in which a flattened wing of fibrous, papery tissue develops from the ovary wall. It is sometimes called a key and is often referred to as a wingnut, helicopter, whirlibird, whirligig, polynose etc.

Within the megagametophyte one of the two sperms unites with the egg, forming a zygote, and the second sperm enters the central cell forming the endosperm mother cell, which completes the double fertilization process.

A small bract is called a bracteole or bractlet. Technically this is any bract that arises on a pedicel instead of subtending it as in Adhantoda.
Bracts that appear in a whorl subtending an inflorescence are collectively called an involucre. An involucre is a common feature beneath the inflorescences of many Apiaceae, Asteraceae, Dipsacaceae and Polygonaceae.

Spike inflorescence has a long peduncle which bears a number of sessile flowers in acropetal succession. Example: Amaranthus.

A hesperidium is a modified berry with a tough, leathery rind. The peel contains volatile oil glands in pits. The fleshy interior is composed of separate sections, called carpels, filled with fluid-filled vesicles that are actually specialized hair cells. Oranges and other citrus fruits are common examples.

It is a simple fleshy fruit and generally many-seeded. It develops from an inferior, monolocular ovary, having parietal placentation. e.g. cucumber, watermelon.

Presence of multicapellary, syncarpous and multilocular gynoecium. The ovules are borne all over the inner surface of the ovary. Superficial placentation is also known as the laminar placentation. This type of placentation is observed in Nymphaeceae and Butomaceae.