Plant Kingdom Test - 12

In diplontic life cycle,  diploid sporophyte is the dominant, photosynthetic, 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 exhibits diplontic life cycle.

The sperms or male gamete of Cycas are the largest in the biological world. It is top shaped .In Cycas revoluta the size of the sperm ranges between 180 to 210 μm and they are clearly visible to the naked eye. 

In haplontic life cycle , the dominant, photosynthetic phase is the free-living gametophyte which is seen in Volvox, Spirogyra and Chlamydomonas.

A dominant, independent, photosynthetic, thalloid or erect phase of Bryophytes and pteridophytes is represented by a haploid gametophyte

In bryophytes the dominant phase in the life cycle is the gametophytic plant body. However, in pteridophytes, the main plant body is a sporophyte which is differentiated into true root, stem and leaves.

All seed-bearing plants i.e.,gymnosperms and angiosperms follow diplontic alternation of generation where the diploid sporophyte is the dominant, photosynthetic, independent phase of the plant. The gametophytic phase is represented by the single to few-celled haploid gametophyte.

Megasporangium of seed plants are called ovule. Ovule is present inside the ovary which become seed on maturation after fertlization. It produce megasporocytes or Megaspore mother cells  that yield megaspores. 

Angiospermic plants have roots to hold the soil and remain erect. Similarly Rhodophytes have holdfast by which they remain attached with substratum to absorb water and minerals.

Fusion of two polar nuclei with one male gamete is called triple fusion. Primary endosperm nucleus is formed by  triple fusion and  divide mitotically to form endosperm.

Gymnosperms and lower vascular plants have sieve cells as their sieve elements, while sieve tubes and companion cells are characteristic of flowering plants (angiosperms).Phloem transport food form leaves to all other parts of plants.