Question

The second stage of hydrosere is occupied by plants like
A) Typha
B) Salix
C) Vallisneria
D) Azolla

Answer 1

Hydrosere is a plant succession that leads to the change in the species structure in the ecology over time and mainly occurs in the area of freshwaters as the area near the freshwater
will form a woodland.

Complete step by step answer: There are various intermediate stages in a hydrosere where the freshwater area will develop into a woodland finally. Some stages are so short that they can hardly be observed.
-The first stage is the Phytoplankton stage where phytoplankton, diatoms, blue-green algae, etc. colonize in the pond or lake, and when they die their dead bodies form humus, and slowly the soil
builds up and the pond becomes shallower.
-The second stage is the Submerged stage where Myriophyllum, Vallisneria, Elodea, Hydrilla, and Ceratophyllum form as the rooted submerged species can grow more due to the pond becoming shallower and allows more rapid changes.
-The third stage is the floating stage where floating plants like Nymphaea, Nelumbo and
Potamogeton are rooted in the mud and these plants decay to form more organic mud and making
the ponds shallower.
-The fourth stage is the reed swamp stage where plants like Phragmites (reed-grasses), Typha (cattail), and Zizania (wild rice) invade the pond and form red sweep and converts the surface of the pond into marshy land.
-The fifth stage is the sedge-meadow stage where Cyperaceae and Gramineae colonize and allows
extending the vegetation and then later edge peat accumulates above the water level and soil is no
longer totally waterlogged.
-The last two stages are the woodland stage and forest stage where Lantana, Salix, Populus colonize in the woodland stage, and in the forest stage, Tropical rainforests, tropical deciduous forests are formed.
Hence, the correct answer is option (C).

Note: In the Submerged stage the submerged species colonize and allow the successional changes to be rapid and mainly autogenic as organic matter accumulates and inorganic sediment enters the lake and is trapped more quickly by the net of plant roots and rhizomes growing on the pond floor.