Whereas lower vascular plants, such as club mosses and ferns, are mostly homosporous (produce only one type of spore), all seed plants, or spermatophytes, are heterosporous. They form two types of spores: megaspores (female) and microspores (male).
How is heterospory related to seed habit?
The adoption of heterospory and the retention and germination of a single megaspore within megasporangium to form a female gametophyte, led to the phenomenon of “seed habit”, a characteristic feature of the spermatophytes. A seed is that ovule which contains an embryo developed as a result of fertilization.
What is heterospory give example?
Heterospory is referred to the production of two types of spores, which differ in size. The smaller male microspores and bigger female megaspores. Gymnosperms are heterosporous, e.g. Pinus, Cycas. … Pteridophytes are mostly homosporous but a few genera, e.g. Selaginella and Salvinia are heterosporous.
What do you mean by Hetrospory?
Heterospory is the production of spores of two different sizes and sexes by the sporophytes of land plants. The smaller of these, the microspore, is male and the larger megaspore is female. … This occurred as part of the process of evolution of the timing of sex differentiation.
Is pteris Homosporous or heterosporous?
All bryophytes are homosporous and all gymnosperms are heterosporous. This condition is advanced as sexual dimorphism result in cross fertilization. Primitive or earlier Pteridophyta are homosporous later pteriodophytes are heterosporouse. g., Dryopteris, Pteris homosporous Selaginella, Salvinia-heterosporous.
What is precursor of seed habit?
The development of the zygotes into young embryos take place within the female gametophytes. This event is a precursor to the seed habit considered an important step in evolution.
What is seed habit?
‘Seed habit’ involves the origin and formation of seed from non-seed bearing. plant and it involves in following changes in non-seed bearing plants:– 1. Production of two kinds of spore i.e. evolution of heterospory.
What is the origin of seed habit?
Meaning of Seed Habit:
Seed is a ripened or fertilised ovule. … Thus seeds provide parental care to the land plants, where megagametophyte is retained within the indehiscent megasporangium and is well-protected by the integument.
What is heterospory in selaginella?
Heterospory is a character of Selaginella. In this plant, two different kinds of spores are produced i.e. microspores formed in microsporangia and megaspores formed in megasporangia. Microspores produce male gametophytes and megaspores produce female gametophytes. Heterospory is essential for seed habit.
What is a gymnosperm plant?
gymnosperm, any vascular plant that reproduces by means of an exposed seed, or ovule—unlike angiosperms, or flowering plants, whose seeds are enclosed by mature ovaries, or fruits.
Why gametophyte is called so?
The gametophyte is the sexual phase in the life cycle of plants and algae. It develops sex organs that produce gametes, haploid sex cells that participate in fertilization to form a diploid zygote which has a double set of chromosomes.
What is heterospory short answer?
Heterospory is a phenomenon in which two kinds of spores are borne by the same plant. These spores differ in size. The smaller one is known as microspore and the larger one is known as megaspore. The microspore germinates to form the male gametophyte and the megaspore germinates to form the female gametophyte.
Is Strobili or cones are found in pteris?
It belongs to pteridophytes which are the first terrestrial plants to possess vascular tissues – xylem and phloem. It belongs to the Sphenopsida class of pteridophytes. Sporophylls are compactly arranged into structures called strobili or cones.
What is the role of heterospory in the evolution of seed?
One of the most important advantages of heterospory is the formation of seed habitat. … In heterosporous plants, the male and female gametangia are separated both in time and space. This reduces the chance of self-fertilization and increases the chance of variability in the progenies.
What is Telome explain the Telome theory?
telome theory The theory that the leaves (megaphylls) of ferns and seed plants evolved by the modification of terminal branches (telomes) of stems. It envisages that firstly, instead of the primitive equal (dichotomous) branching of the stem, there developed a main axis with lateral side branches.
Which plant group shows seed habits?
Seed habit is seen in plants from pteridophytes. It is not seen in other lower plants. Pteridophytes are the most advanced flowerless and seedless plants. One must know that they form the largest living group of primitive vascular plants.
Which is an essential for the formation of seed?
A seed is formed when fertilised ovule divides by mitosis. After reaching stigma, the male gametes fuses with the egg in the ovule and forms a zygote. … Thus fertilization takes place and so formed zygote divides and develops into an embryo.
Which group of plants shows events as precursor to seed?
Heterosporous pteridophytes show certain characteristics, which are precursors to the ‘seed habit’ in gymnosperms.
Why does the primary root appear first?
root anatomy and function
The primary root, or radicle, is the first organ to appear when a seed germinates. It grows downward into the soil, anchoring the seedling. … …from the embryonic root (radicle), which grows out of the seed after the seed has absorbed water. This is the primary root of a new plant.
What is Homosporous?
homosporous. / (hɒˈmɒspərəs, ˌhəʊməʊˈspɔːrəs) / adjective. (of most ferns and some other spore-bearing plants) producing spores of one kind only, which develop into hermaphrodite gametophytesCompare heterosporous.
What is annulus in pteris?
The region of the wall of a fern sporangium that is specialized for spore dispersal.
Is marsilea is Homosporous?
They are homosporous but a few plants are heterosporous also e.g., Isoetes, Selaginella, Marsilea, Regnellidium, Pilularia, Azolla and Salvinia. In Selaginella the sporangia are borne in relation to sporophylls which constitute a strobilus. … In ferns the sporangia are borne in sori on the sporophylls.