Morphological, Anatomical & Physiological Adaptations of Hydrophytes Aarif Maqbool Department of Botany Govt. Degree College Bijbehara

Learning Objectives: What is adaptation? Plant groups based on adaptations. Hydrophytes Classification of Hydrophytes Adaptations of Hydrophytes Morphological Adaptations of Hydrophytes Anatomical Adaptations of Hydrophytes Physiological Adaptations of Hydrophytes

What is an Adaptation? Any feature of an organism or its part which enables it to exist under conditions of its habitat is called adaptation. Adaptations are for: Withstand adverse conditions of an environment. Utilize maximum benefit of environment.

Plant groups based on adaptations Classification of plants: On the basis of their water requirement, Warming (1909) primarily recognized three major groups of Plants. Hydrophytes: Plants which live in water. Xerophytes: Plants that live in conditions where water is scare. Mesophytes: Land plants living in environment with moderate amount of moisture.

Hydrophytes: Free floating hydrophytes Submerged floating hydrophytes Hydrophytes are plants that grow in regions, where, there is plenty of water supply or wet soils. The hydrophytes are generally classified into the following five categories: Free floating hydrophytes Submerged floating hydrophytes Rooted submerged hydrophytes Rooted hydrophytes with floating leaves Rooted emergent hydrophytes

Free floating hydrophytes: They float freely on the surface of water. e.g., Eichornia, Pistia, Wolffia, and Lemna) Eichornia Wolfia Lemna

Submerged floating hydrophytes: These are the plants in contact with only water, being completely submerged & not rooted in mud e.g., Utricularia, Ceratophyllum, Najas, etc. Najas Ceratophyllum

Rooted submerged hydrophytes: They are submerged in the water but roots are fixed. E.g., Hydrilla, Vallisneria, Potamogeton. Hydrilla Vallisneria Potamogeton

Rooted hydrophytes with floating leaves: The roots of the plants are fixed in the soil while leaves are floating on the surface of water. E.g., Nymphaea, Victoria, Trapa. Nymphaea Victoria Trapa

Rooted emergent hydrophytes: They grow in marshy areas Rooted emergent hydrophytes: They grow in marshy areas. Plants that partly in water and partly in air. E.g., Ranunculus, Sagitaria, Typha. Typha Sagitaria Ranunculus

Adaptations of Hydrophytes: Morphological Adaptations Anatomical Adaptations Physiological Adaptations

Morphological Adaptations of Hydrophytes: Roots: Poorly developed or absent in plants like Wolfia, Ceratophyllum. Root hairs are absent in certain plants. Root caps are replaced by root pockets(Eichornia, pistia). The roots act as a balancing and anchoring organs. Aerial roots are developed in certain plants like Jussiaea.

Stem: It is long, slender & thin. It is green in color so carry out photosynthesis. In some floating forms stem is spongy (Eicchornia). Stem helps in reproduction by stolons and offsets. Stem is a rhizome in rooted plants with free floating leaves E.g.,: Nymphaea and Nelumbo.

Leaves: are deposited with wax •In many floating forms leaves are deposited with wax (Nymphaea,Victoria regia). •In submerged forms they are reduced and thin. •In emergent hydrophytes leaves are of two types dissected leaves in water and aerial leaves are well developed. •The spongy petiole is observed in Eicchornia which help in buoyancy. •The leaves are dissected in Ceratophyllum.

Anatomical Adaptations: Cuticle is absent. Epidermis is single layered made up of thin walled parenchyma cells. So they can absorb water. Cortex is well developed made up of parenchyma cells. There are large air spaces surrounded by parenchyma cells called aerenchyma cells. They help in gaseous exchange and give buoyancy to plants.

Anatomical Adaptations: Mechanical tissues are absent to avoid rigidness of stem Vascular tissues are poorly developed. Xylem consists of only tracheids. In Nympheaea, special type of star shaped lignified cells are present which give mechanical support. In submerged leaves stomata are totally absent so the exchange of gases is carried out by all the cells. In floating leaves stomata are present on upper epidermis.

Physiological adaptations These plants have low rate of absorption of minerals. Transpiration is negligible. Rate of photosynthesis is low.

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