The variety of flora Classification of plants

The variety of flora. Classification of plants by the presence of indicators of physiological and anatomical adaptations to specific environmental conditions 409 -1 Lena Krasko

v Plant ecology is the study of relationships between plants and their physical environment. v Plants have adaptations to help them survive (live and grow) in different areas. v Adaptations are special features that allow a plant or animal to live in a particular place or habitat.

v The way in which plants and animals grow and carry out their different activities is a result of several abiotic factors. These factors are water, light, temperature, soil, atmospheric gases, wind and other factors. v Plants are usually classified into ecological units based on the characteristics evolved in order to survive in a particular ecosystem. This is known as ecological classification.

Vegetation types according to water regime Hydrophytes Plants that have adapted to living In or on aquatic environments. Mesophytes plants adapted to medium moisture levels Xerophytes Plants adapted to survive in very dry habitat

Hydrophytes • • • Cuticle generally absent or thin Stomata are open most of time An increased number of stomata, that can be on either side of leaves A less rigid structure (water pressure supports them) Leaves thin, narrow, linear, some with long petioles and large lamina, covered with wax or haris Large flat leaves on surface water and air sacs for flotation. Roots generally unbranched, without root hairs or even absent Specialized roots designed to take in oxygen. Large intercellular spaces to reduce weight. Examples: water lily, water hyacinth. Water chestnut , reedmace

Mesophytes • • • Root system well developed, tap or fibrous roots with root haris Stem is rigid and stout Leaves large, thin, generally without waxy surfaces Leaves are broad to provide a large surface area for maximum light absorption Cuticle developed to reduce water loss & protect internal tissues from heat. Stomata on one or both the surfaces. Palisade well developed and differentiated Chlorophyll mostly in leaves. Epidermal cells thick. Meachanical and vascular tissues well developed Examples: daffodil, rose, corn, clover

Xerophytes • • • Root system generally very deep, extensive, reaching deeper layers of soil; hard, woody Stem much dwarfed, branched, sometimes underground. Leaves small or modified into spines or leathery and thick with shining surface and waxy coating, covered with hairs Aerenchyma lacking. Cuticle thick, well developed, Stomata less in number, generally on lower surfaces of leaves. Epidermal cells conspicuously thick-walled. Mechanical and vascular tissues very well developed Shedding leaves in dry, cold season. Examples: cacti , aloe, agave, spurge

Vegetation types according to light Heliophytes Plants which grow well in bright sunlight Sciophytes Plants which grow well in shady conditions

Heliophytes • • • Have a high rate of photosynthesis as well as respiration. The leaves thinner and more widely spaced Vertical orientation of leaf blades Thicker stem, Well developed conducting elements and mechanical tissues, Longer root, Shorter internodes, More branching, Lower chlorophyll content, Higher respiration rate, Higher osmotic pressure Examples: sugar cane, sunflower and maize.

Sciophytes • • • Have lower rate of photosynthesis and more a lower rate of respiration. Shade leaves are thinner, weakly lobed, have large surface area per unit weight, Fewer stomata and less support and conduction tissues. Have low growth rates, Cuticle generally thin Epidermis is thin, single layer Examples: mint, currant, sorrel

Vegetation types according to temperature Megatherms plant that needs a constant and high temperature for their growth throughout the year Mesotherms plants which can tolerate low temperature for a longer or a shorter period of the year Microtherms plants that grow very well under low temperature but can not tolerate high temperature Hekistotherms Plants require a constant low temperature for there growth

Plant adaptation to high temperatures: • • The transition to a state of suspended animation, Development of a thick cuticle, multilayered epidermis, dense pubescence, contribute to the reflection of sunlight. Reduce surface body of the plant due to fall of the branches, reduction of the leaves and curling of leaf blades Development of heat-insulating layer, for example, a light crust Enhanced transpiration Increase in the viscosity of the cytoplasm, High concentrations of substances that reduce the amount of free water (mucus, carbohydrates, organic acids, chlorides, sulfates, etc. )

Plant adaptation to low temperatures: • • • The transition to the resting state. Woody plants shed their leaves, in perennial herbaceous plants die back above ground shoots, in annual grasses - all vegetative organs. Development of special forms of growth. (Dwarfism, creeping and polster shape). Contractile roots bury overwintering of plants in soil. Development of protective covers (periderm) Formation of a thick cuticle, downiness leaves, Development of glandular hairs, Forming rosettes of leaves at the ends of shoots, protecting the growing point. Reduction in the intensity of physiological processes, Reducing the number of free water by binding to its sugar and hydrophilic colloids (amino acids, salts of sodium and potassium).

Vegetation types according to soil types Lithophyte - plants rocky surfaces Psammophyte - plant of sandy soils Chasmophyte - higher plants gravelly soils Halophytes - adapted to saline soils Acidophyte - plants that do best in soils that are very acidic. Metallophytes - plants that require soil with lots of metals present.

Lithophyte • Feed off moss, nutrients in rain water, litter, and even their own dead tissue. • Roots are aerial to help in absorption of water from the atmosphere. • Development of special forms of growth. (Dwarfism, creeping and polster shape). • Examples several paphiopedilum orchids, the pitcher plant nepenthes campanulata, and several utricularia species Chasmophyte • Contractile roots contributing to their burial and retention of plants on dry soil • Examples cottonwood, lithops Psammophyte • Shallow or deep-seated roots. Shallow root system is located in the upper soil layer and an unusually branched. • Saxaul , aristide cirrus

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