Question

The peristomial teeth in Funaria are:
A. Hydric
B. Xeric
C. Mesic
D. Hygroscopic

Answer 1

HINT:
Peristome in mosses is the specialised structures in sporangium which allow the gradual release of spores. When the spores inside the capsule are matured, the operculum (the lid) falls off and reveals an opening called stoma (mouth) which is surrounded by one or two peristomes.

COMPLETE STEP BY STEP ANSWER:
Each peristome consists of triangular "teeth" which are formed from the remnants of dead cells. There are 16 such teeth in each peristome. Both of the peristomes are separated from each other and are able to fold in or fold back to cover or expose the stoma respectively. This condition is called arthrodontous. Funaria belongs to bryophyta, where the sporophyte is differentiated into foot, seta and capsule. Funaria has two rings of peristomial teeth containing 16 teeth in each ring (total of 32 peristomial teeth) around the mouth of the capsule. The peristomial teeth of Funaria can change their shape depending on the climate i.e; whether the conditions are dry or wet. Such peristomial teeth are called hygroscopic.
Thus, the correct answer is hygroscopic.

Option ‘D’ is correct

NOTE:
In some mosses, the peristomial teeth are solid and composed of dead cells. Such peristomial teeth are called nematodontous. For example, Polytrichum.
The arthrodontous peristome has two subtypes:- haplolepidous and diplolepidous. The haplolepidous peristome has single ring of 16 peristomial teeth whereas in diplolepidous, there are two rings, an inner endostome and an outer exostome. In some mosses, the peristomial teeth are absent in their capsule, these mosses still undergo cell division but the teeth are not fully developed.