BOTANY. PLANT MORPHOLOGY - O. A. Shevchuk - 2014

PLANT LIFE FORMS

Life form (biomorph) is the external appearance (habitus) of plants that has developed under the Influence of Environmental factors and become genetically fixed.

Environmental factors are the totality of environmental conditions that affect a particular Organism. They are divided into abiotic, biotic, and anthropic factors.

Abiotic factors include climatic environmental factors (METABOLISM/18.html">The Influence of moisture, warmth, light, etc.), edaphic factors (soil Composition and Structure, Water), and geomorphological factors (relief). Biotic factors encompass the Influence of other plants and animals on plant organisms. Anthropic factors refer to The impact of human activity.

Ecomorph is a plant life form that takes shape under the influence of specific environmental conditions and is reflected in its Morphology.

Many schemes and classifications of Plant life forms are described in literature. For morphological correlation, the most suitable and accessible is the Classification by the Danish botanist C. Raunkiær, which distinguishes the following life forms: phanerophytes — a plant life form in which renewal buds are situated high above the soil surface (oak, beech, ash, pine, spruce, buckthorn, hazel, guelder rose); chamaephytes — a plant life form in which renewal buds are located close to the ground surface and protected by scales, forest litter, and in winter by snow cover (cowberry, heather, bilberry, thyme); hemicryptophytes — a plant life form of perennial grasses whose renewal buds are formed close to the soil surface (wild strawberry, dandelion, buttercup); cryptophytes — a plant life form of perennial grasses whose renewal buds are located in tubers, rhizomes, bulbs, etc. (potato, lily of the valley, tulip); therophytes — a plant life form in which renewal buds are contained within seeds from which a new plant organism develops (shepherd's purse, hemp, rye, wheat, oats, poppy).

According to their structure and SHOOT lifespan, plants are divided into herbaceous and woody. In most herbaceous plants growing in the temperate zone, above-ground shoots exist for a single growing season and then die off completely or only in their apical part.

Depending on their lifespan, herbaceous plants can be annual, biennial, or perennial. Annual plants complete their development cycle within one year. Biennial plants are those whose development cycle spans two years: in the first year, they form vegetative Organs and accumulate nutrient reserves in their roots; In the second year, they flower and die after producing fruit. These include many cultivated plants (carrot, radish, beet, etc.). Perennial herbaceous plants have a development cycle lasting more than two years; every year, above-ground shoots develop from renewal buds, living for one year and dying at the end of the growing season. In plants of temperate and moderately cold climates, renewal buds are mostly located underground — on rhizomes, tubers, bulbs, corms, or less frequently, they are elevated to the soil surface (in many rosette plants) or raised above it. The plant parts bearing renewal buds live for many years or, dying in spring after shoots regrow, are formed anew by autumn.

Woody plants possess perennial, highly lignified above-ground shoots that do not die off in winter. They are represented by trees and shrubs. Trees are plants at least 2 m tall with a well-developed lignified main ROOT and shoot — the trunk, which usually reaches a significant size and forms a crown consisting of numerous lateral branches. In shrubs, the main shoot is usually short-lived or poorly developed. Numerous sturdy shoots, among which no single main one stands out, develop from axillary and adventitious buds at its base. Shrubs are generally shorter than typical trees. Subshrubs (dwarf shrubs) have perennial, poorly developed stems that remain thin and low-growing (up to 50 cm tall) throughout their life. In winter, they are completely or almost completely covered by snow (blueberry, lingonberry, cranberry, etc.). Half-shrubs are perennial plants over 1 m tall whose shoot bases become woody and persist for several years, while the upper PARTS OF THE shoots are herbaceous and die off for the winter. New shoots grow in the following spring from axillary buds located on the overwintering shoot parts (some species of Ephedra, Astragalus, Genista, etc.). A subshrub (half-shrublet) is a low-growing half-shrub that does not reach a height of one meter, with most of its above-ground shoots dying off annually (some species of wormwood, etc.).

Under extreme living conditions (deserts, tundras, high altitudes), these plants form cushion growth forms. Cushion plants (such as milkvetch, wormwood, lavender, spurge, dracaena) are characterized by very slow shoot growth and significant leaf reduction. The division of plants into the aforementioned life forms is quite conventional, and transitional forms exist between them.