Plant Biology: Anatomy, Physiology, and Reproduction

Dehiscence is the opening, at maturity, of a plant structure, such as a fruit, anther, or sporangium, to release its contents. Sometimes this involves the complete detachment of a part. Structures that open in this way are said to be dehiscent.

Gibberellins (GAs) are plant hormones that regulate growth and influence various developmental processes, including stem elongation, germination, dormancy, flowering, sex expression, enzyme induction, and leaf and fruit senescence.

Xerochasy is dehiscence that occurs upon drying.

A perennial plant is a plant that lives for more than two years.

Semelparous organisms reproduce only once in their lifetime, such as annual plants (including all grain crops), and certain species of salmon, spiders, bamboos and centru plants. Often, they die shortly after reproduction.

Galls or cecidia are outgrowths on the surface of lifeforms caused by invasion by other lifeforms, such as parasites or bacterial infection. Plant galls are abnormal outgrowths of plant tissues and can be caused by various parasites, from fungi and bacteria to insects and mites.

Epicormic buds lie dormant beneath the bark, their growth is suppressed by hormones from active shoots higher up the plant.

A spadix is a form of spike in which the florets are densely crowded along the axis. They are enclosed or accompanied by a highly specialized bract called a spathe and are a characteristic of the Araceae family.

Adventitious roots arise out-of-sequence from the more usual root formation of branches of a primary root, and instead originate from the stem, branches, leaves, or old woody roots. They commonly occur in monocots and pteridophytes, but also in many dicots, such as clover (Trifolium), ivy (Hedera), strawberry (Fragaria) and willow (Salix). Most aerial roots and stilt roots are adventitious.

The epidermis is the outer layer of cells covering the leaf. It forms the boundary separating the plant's inner cells from the external world. The epidermis serves several functions: protection against water loss by way of transpiration, regulation of gas exchange, secretion of metabolic compounds, and (in some species) absorption of water.

Here the leaves form a rosette. A rosette is a circular arrangement of leaves with all the leaves at the same height.

Pinnately compound leaves have the leaflets arranged along the main or mid-vein.

The large roots that have undergone considerable secondary thickening and provide mechanical support to woody plants and trees.

These are the roots of parasitic plants that can absorb water and nutrients from another plant, such as in mistletoe (Viscum album) and dodder.

These are the roots that have undergone secondary thickening and have a woody structure. These roots have some ability to absorb water and nutrients, but their main function is transport and to provide a structure to connect the smaller diameter fine roots to the rest of the plant.

Adventitious roots arise out-of-sequence from the more usual root formation of branches of a primary root, and instead originate from the stem, branches, leaves, or old woody roots. They commonly occur in monocots and pteridophytes, but also in many dicots, such as clover (Trifolium), ivy (Hedera), strawberry (Fragaria) and willow (Salix).

These specialized aerial roots enable plants to breathe air in habitats that have waterlogged soil. The roots may grow down from the stem, or up from typical roots.

A piece of detached twig or shoot. The scion usually contains two or three buds, although it may contain more. When the scion is only a single bud, the form of grafting is known as budding.

Development of an embryo directly from an egg cell without fertilization is called parthenogenesis.

Division, is a method of asexual plant propagation, where the plant (usually an herbaceous perennial) is broken up into two or more parts. Both the root and crown of each part is kept intact.

Grafting is the act of joining two plants together. The upper part of the graft (the scion) becomes the top of the plant, the lower portion (the understock) becomes the root system or part of the trunk. Although grafting usually refers to joining only two plants, it may be a combination of several.

In this type, the flowers are replaced by bulbils or other vegetative propagules, which frequently germinate while still on the plant. Vegetative apomixis is important in Allium, Fragaria, some grasses, etc.

Mound (stool) layering is useful with heavy-stemmed, closely branched shrubs and rootstocks of tree fruits. Cut the plant back to 1 inch above the soil surface in the dormant season. Dormant buds will produce new shoots in the spring. Mound soil over the new shoots as they grow . Roots will develop at the bases of the young shoots. Remove the layers in the dormant season e.g., apple rootstocks, spirea, quince, daphne, magnolia, and cotoneaster.

Another type of  vegetative reproduction is the production of bulbs. Plants like onion (Allium cepa), hyacinth (Hyacinth), narcissus (Narcissus) and tulips (Tulipa) reproduce by forming bulbs.

A corm is a short, vertical, swollen underground plant stem that serves as a storage organ and used by some plants to survive winter or other adverse conditions such as summer drought and heat (estivation).