Table: Comparison between dicots and monocots
Features Dicots Monocots
Cotyledons Usually two One cotyledon
Flowers Penta or tetramerous Trimerous
Pollen grains Three germ pores Single germinal furrow
Leaf venation Reticulate Parallel except a few
Primary root Often long lived forming tap root system. Adventitious roots occur
in some.Short-lived
Tap roots absent, instead adventitious roots are found.
Stem tissue Concentric arrangement of epidermis, cortex, endodermis, pericycle,
pith, etc.Undifferentiated, a ground tissue occurs.Vascular bundles of stem In a ring, cambium (open), thus secondary growth present. Scattered, cambium is absent (closed).
Root Pith absent or small. Vascular bundles 8 or less. Pith present. Vascular bundles more than 8.
Xylem vessels Polygonal Rounded
Flowering plants or angiosperms have exploited insects, birds and several other animals as agents of pollination, fruit and seed dispersal. It is one
major reason for present day dominance of flowering plants.ALTERNATION OF GENERATION
- During the life cycle of sexually reproducing plants, there
is an alternation between gamete producing haploid
gametophyte and spore producing diploid sporophyte. - Different plant groups as well as individuals representing
them, differ in the following patterns : - Haplontic life cycle - Sporophytic generation is
represented by one-celled zygote. Meiosis in zygote results
in the formation of haploid spores. The haploid spore forms
free living gametophyte by mitosis. It is represented by many
algae such as Volvox, Spirogyra and Chlamydomonas. - Diplontic life cycle - Diploid sporophyte is dominant,
photosynthetic and independent phase of the plant. The
gametophytic phase is represented by the single to few-
celled haploid gametophyte. All seed bearing plants,
i.e., gymnosperms and angiosperms and an alga Fucus
exhibit this kind of pattern. - Haplodiplontic life cycle - Bryophytes and pteri-
dophytes exhibit this kind of pattern. In bryophytes, a
dominant independent, photosynthetic, thalloid phase
is represented by a gametophyte and it alternates with
short-lived multicellular sporophyte totally or partially
dependent on the gametophyte for its anchorage and
nutrition. - In pteridophytes, the diploid sporophyte is represented by a dominant, independent, photosynthetic, vascular plant body. It
alternates with multicellular, saprophytic / autotrophic, independent but short-lived haploid gametophyte. - Some algal genera such as Ectocarpus and Polysiphonia are also haplodiplontic.
4. What is the meaning of alternation of generation in plants? Briefly describe diplontic life cycle
with examples.
5. What is double fertilisation? It is a characteristic feature of which group of plants?
6. Give the characteristic features of cycadopsida.