Govt. Exams
Entrance Exams
Casparian strips are bands of suberin deposited on the radial and transverse walls of endodermal cells, preventing lateral water movement.
Dicot roots show radial arrangement of vascular bundles with xylem rays alternating with phloem strands.
Mesophyll tissue consists of palisade and spongy parenchyma and is located between the two epidermal layers.
The shift from gametophytic to sporophytic dominance in pteridophytes is advantageous because: (1) Sporophytes with indeterminate growth can produce more spores, increasing reproductive success, and (2) Spores with thick protective walls (sporopollenin) can survive in drier environments, reducing dependence on moisture. This represents a major evolutionary transition.
The archegonium is a flask-shaped female reproductive organ that protects the egg cell and provides a passage (neck canal) for sperm entry, requiring moisture for fertilization.
These characteristics are typical of pteridophytes/ferns: independent sporophyte and gametophyte, sporangia on fern fronds, and reproduction through spores without seeds.
The integument develops from the chalaza end of the nucellus and grows upward to cover the nucellus, leaving only the micropyle opening for pollen entry.
The prothallus (gametophyte) in pteridophytes is homologous to the gametophytic generation in bryophytes as both are haploid structures producing gametes.
Gemma cups in liverworts produce small vegetative bodies (gemmae) that are dispersed for asexual reproduction, allowing rapid colonization.
Angiosperms can be monocots (one cotyledon) or dicots (two cotyledons), so not all angiosperms have two cotyledons.
