Botany and Plant Science

In the life cycle of Dryopteris, the asexual sporophyte is the dominant individual. This is perennial and evergreen and differentiates into rhizome (stem), roots and leaves ( fronds). When the fronds mature these become fertile and are called as sporophylls since they contain sori. In each sorus stalked sporangia is present arising from the placenta, the swollen outgrowth on the divisions of the pinna or leaflets.

Strobilus is called the fertile branch, because it bears the reproductive structures such as microsporophylls and megasporophylls.

In Dryopteris, the neck consists of a wall or jacket layer of 4 vertical rows of sterile neck cells. The neck cells enclose a central neck canal. They contains a single, long neck canal cells with two nuclei.

Selaginella and Salvinia are considered the first plants to exhibit a significant step toward the evolution of seed habit because embryo develops in female gametophyte which is retained on parent sporophyte. It occurs because Selaginella and Salvinia both are heterosporous, i.e., these plants produce two kinds of spores, macro (large) and micro (small) spores. In the heterosporous species, the female gametophyte remains on the parent sporophytes for variable periods. The development of the zygotes into young embryos takes place within the female gametophytes. This event is a precursor to the seed habit (tendency towards seed formation) considered an important step in evolution. Hence, heterospory leads to seed habits in plants.

The presence of Ligule - a small tongue shaped appendage on the adaxial side of the leaf near the leaf base is a distinctive feature of the Selaginella. This consists of elongated secretory cells the glossopodium which tends to keep the sporangium wet. Another distinctive feature is the cones or strobilus on which the sporophylls are present.

The megaspores and microspores germinate and give rise to female and male gametophytes, respectively. The female gametophytes in these plants are retained on the parent sporophytes for variable periods. The development of the zygotes into young embryos take place within the female gametophytes. 

The four megaspores derived from a megaspore mother cell may not always be functional. i.e. In S.rupestris single megaspore is functional.

The retention of the megaspore and the development of the embryo within the female gametophyte, which remains attached to the parent sporophyte, is a crucial evolutionary step toward the seed habit.

In Dryopteris, on the lowerside of the leaflet an outgrowth is present. It consists of a stalk like placenta and a flap, that protects group of sporangia. This is called as true indusium.

In Dryopteris, the annulus and the stomium help in the dehiscence of the sporangium and dispersal of spores. At maturity, the sporangium dehisces by drying action, which exerts pressure on mouth assisted by shrinkage of the annulus. Lastly mouth of sporangium open and spores are liberated.

• Colour of rose petals is due to water-soluble pigment present in the vacuoles.
  
• The plant vacuoles consist of various water-soluble pigments such as carotenoids, anthocyanins and xanthophylls etc.
• Anthocyanins are also water-soluble pigments which are red, purple, or blue in colour depending on the pH (blueberry, raspberry etc).
  
• The colour of flower petals (red, pink, blue and purple) is mainly from the pigments called anthocyanins.
  
• So, the correct answer is 'Vacuoles'.

The antheridium (male organ) is located on the lower surface of the fern prothallus and the archegonium (female organ) is located on the upper surface of the fern prothallus.

Cryptogams are plants, that reproduce by spores without flowers or seeds but angiosperms possess flowers and seeds. Angiosperms are more advanced than the gymnosperms. They consist of covered seeds as compared to the naked seeds of the gymnosperms. Angiosperms bear true fruits. They show characteristics of double fertilization.

The spermatophyta comprises of all those land plants that produce flowers and seed. In angiosperms, and other seed plants, gametophytes are not independent seed plants, instead they are small structures found embedded within the sporophyte.

Stele can be defined as the central core of the stem and root of a vascular plant, consisting of the vascular tissue (xylem and phloem) and associated supporting tissue.