Intermediate UNIT-VII (First Year) Only one chapter, Plant Ecology is included in the Unit VII. Interaction of plants, with other plants and animals and with their environment is explained very briefly in this chapter. Interaction of plants can be studied at different levels like individual plants, group of similar plants (populations) and groups of different plants (communities). Eugen Warming's classification of plant communities on the basis of their water requirements and their adaptations is given elaborately in this chapter All the information given here is already studied by the student in the earlier chapters like Morphology (5) and Anatomy (12), but with a different approach. For all types of examinations this information is essential. For the student it will be easier and interesting if studied properly. As it is an applied topic more understanding questions are possible from this chapter. Many statements are given and the reasoning is left to the students understanding .
The four levels of biological organizations with their increasing variation and complexity areorganisms, populations, communities, biomes.
Desert, rain forest, grasslands and tundras are some examples of biomes.
Adaptations can be seen more in plants rather than in animals.
As a result of a long time evolutionary process many adaptations are genetically fixed and can be
seen generation after generation.
Plants growing in sunlight and shade conditions are heliophytes and sciophytes respectively.
Eugen Warming classified plants based on water requirements.
Hydrophytes with no contact with soil are free floating and submerged suspended plants.
Salvinia is a Pteridophyte with leaves modified to appear like roots.
Plants with contact with water and soil are rooted hydrophytes and submerged rooted plants.
Hydrilla is a monoecious plant and Utricularia is an insectivorous plant without roots.
Roots, root hairs, root caps are poorly developed or absent in hydrophytes.
Root caps in Pistia, Eichornia and Lemna are replaced by air pockets. All these three show balancing roots.
In hydrophytes like Nymphea, Nelumbo, and in aquatic ferns stem is rhizome.
Cuticle is generally thin. In completely submerged water plants cuticle is absent.
Epidermal cells show plastids and are assimilatory.
Epistomatous in floating leaves. Astomatous in completely submerged water plants.
Aerenchyma is the most important feature of hydrophytes.
Mechanical tissue and xylem is less developed as they do not need mechanical support in water.
In Hydrilla stem more phloem is present. Xylem cavity is present to help them float in the water.
Mesophytes show least modifications. Xerophytes show maximum modifications.
Mesophytes are very extensive on the surface of the land as extreme conditions are isolated.
Ephemerals appear like mesophytes.
All plants with storage roots, storage stems and storage leaves are xerophytes.
Non-succulents are true xerophytes. Casuarina, Ficus are xerophytes.
Extensive roots, well developed root hairs and root caps are xerophytic adaptations.
Spines, Thorns, Phylloclades, Phyllodes, Scaly leaves are xerophytic modifications.
Thick epidermis, multiple epidermis, impregnation of silica in epidermal cells, hypostomatous condition, sunken stomata are xerophytic adaptations.
Secretions of latex, gums, resins, tannins are xerophytic adaptations.
Mechanical tissue and vascular tissue is well developed in xerophytes to absorb more water.
Nerium shows multiple epidermis on both surfaces. Palisade and spongy also distributed below both upper and lower epidermis. Hypostomatous and sunken stomata are present.
In plant succession sequence of communities are specific. Each community is a sere.
Climax community is always a forest.
Hydroseres or Xeroseres ultimately become mesic.
Primary succession is always slow.
Secondary succession begins due to destruction of primary succession as a result of natural or human induced disturbances.
Secondary succession is faster as some soil is already present. Earlier seral stages may appear. Some new species may appear or some species may disappear.
In hydrarch, diatoms are pioneers followed by free floating plants, rooted submerged plants, sedges, grasses and small trees.
In xerarch lichens are pioneers followed by certain bryophytes.
Supporting services are -Soil formation, nutrient cycling, oxygen production. Soil formation accounts for 50% contribution.
Water purification, food protection, Climate regulation are regulatory services.
Honey bees are most important pollinators. Pollination is supporting service.
In plants per every gram organic matter production requires 1.63 grams of CO2.
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