Biologically most resistant plant material is
sporopollenin
cutin
lignin
suberin
A.
sporopollenin
Sporopollenin is biologically most resistant plant material and is present in pollen exine. It is contributed by the tapetum layer of the another wall.
The lack of fruit formation in gymnosperm is due to
absence of fertilization
lack of seeds
naked ovule
sheding of immature seed
In gametophyte of fern
prothallus is independent from sporophyte
prothallus is attached with sporophyte
it is main plant body
a structure attached with rhizome
In living beings ammonia is converted into urea through
ornithine cycle
citrulline cycle
fumarine cycle
arginine cycle