In succulent plants the stomata open in night and close in day. Which among the following would be best hypothesis to explain the mechanism of stomatal action in night only?

(1) CO₂ accumulates, reduces pH, stimulate enzymes resulting in accumulation of sugars.

(2) Increase in CO₂ concentration, conversion of organic acids into starch resulting in the increased conversion into sugars resulting in K⁺ transport.

(3) Low CO₂ concentration accumulates organic acids resulting in the increased concentration of cell sap.

(4) CO₂ used up, increase pH results in accumulation of sugars.

Bark refers to 

(1) Phellem + Phellogen + Phelloderm

(2) Periderm + Cortex

(3) Phellem + Phelloderm + Secondary phloem

(4) Periderm + Cortex + Pericycle + Secondary phloem

The branched sclereids present in hydrophytes are:-
(1) osteosclereids

(2) trichosclereids

(3) macrosclereids

(4) astrosclereids

Why are vascular bundles closed in monocots?

(1) Xylem and Phloem are present

(2) Xylem and phloem occur in separate bundles

(3) Vascular cambium is present between xylem and phloem

(4) Vascular cambium is not present

Given figure shows:-

(a) structure of lenticel
(b) hydathode showing gaseous vapour exchange
(c) fungus reproducing by spore formation
(d) algae reproducing by spore formation

Select the correct pair amongst the following.
(1) Spring wood  - light colour, high density

(2) Spring wood  - dark colour, low density

(3) Autumn wood - light colour, high density

(4) Autumn wood - dark colour, high density

As secondary growth proceeds, in a dicot stem, the thickness of.

(1) sapwood increases

(2) heartwood increases

(3) both sapwood and heartwood increases

(4) both sapwood and heartwood remains the same

The desert grasses, often curls their leaf to minimise water loss due to presence of 

1. Spines

2. Palisade parenchyma

3. Bundle sheath cells

4. Bulliform cells

Tyloses are balloon-like outgrowths in the lumen of secondary xylem tracheids and vessel of duramen region. These are actually:-
(1) outgrowth of vessels of xylem

(2) ingrowth of vessels

(3) outgrowth of parenchymatous cell

(4) swelling of xylem fibres for no function

Pith cavity occurs in the stem of ?
(1) Helianthus

(2) Zea mays

(3) Cucurbita   

(4) Dracaena