STD 12 - 11. organisms and populations — NEET STD 11 Science — Question

Mitosis in plants is seen in....

Species which occupy a similar ecological niche in similar communities occupying different biogeographical regions are

The cut flowers and vegetables can be kept fresh a long period by this plant hormone

Which one of the following statements are correct ?
(i) In flowering plants, tracheids and vessels are the main water transporting element.
(ii) The first formed primary xylem elements are called protoxylem.
(iii) In roots, the proto xylem lies towards periphery and meta xylem lies toward the centre. Such arrangement of primary xylem is called endarch.
(iv) Phloem in angiosperms is composed of sieve tube elements, companion cells, phloem parenchyma and phloem fibers.
(v) The functions of sieve tubes are controlled by the nucleus of companion cells.
(vi) The companion cells are specialized sclerenchymatous cells, which are closely associated with sieve tube elements.
(vii) The sieve tube elements and companion cells are connected by pit fields present between their common transverse walls.
(viii) The companion cells help in maintaining the pressure gradient in the sieve tubes.
(ix) Phloem parenchyma is absent in most of the diocotyledons.
(x) Phloem fibres are made up of sclerenchymatous cells.
(xi) The first formed primary phloem consists of narrow sieve tubes and is referred to as protophloem.
(xii) The outside of the epidermis is often covered with a waxy thin layer called cuticle which prevents the loss of water. Cuticle is absent in roots.
(xiii) Each stoma is composed of two bean-shaped cells known as guard cells. In grasses, those cells are dumb-bell shaped.
Choose the correct option given below :-

Select wrong statement.

Pteridophytes are characterized by

Oxidation of succinate to fumerate in the Kreb's cycle is due to

Which of the following will determines the shape of the cells and provides a strong structural support to prevent the bacterium from bursting or collapsing?