As secondary growth proceeds, in a dicot stem, the thickness of
sapwood increases
heartwood increases
both sapwood and heartwood increases
both sapwood and heartwood remains the same
B.
heartwood increases
In a woody stem, due to secondary growth, secondary xylem constitutes the bulk of the stem and is commonly called wood. Width of secondary xylem increases continuously with the age of the plant.
Older stem have two regions- younger sapwood and older heartwood. Both sapwood and heartwood increase in size initially, but when a tree reaches a certain age, amount of heartwood increases and the amount of sapwood remains constant.
Assertion : Cork prevents the loss of water by evaporation.
Reason : Cork cells contain tannins.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false
Select the correct pair amongst the following
Spring wood- light colour, high density
Spring wood - dark colour, low density
Autumn wood - light colour, high density
Autumn wood - dark colour, high density
In monocot roots which types of vascular bundles are found?
Collateral, conjoint and closed
Radial with exarch xylem
Bicollateral, conjoint and closed
Radial with endarch xylem
Why are vascular bundles closed in monocots?
Xylem and phloem are present.
Xylem and phloem occur in separate bundles.
Vascular cambium is present between xylem and phloem.
Vascular cambium is not present.
Bark refers to
phellem + phellogen + phelloderm
periderm + cortex
phellem + phelloderm + secondary phloem
periderm + cortex + pericycle + secondary phloem
Jute fibres deteriorate quickly because
cellulose content is high
lignin content is high
cellulose content is low
lignin content is low
Periderm includes
cork cambium only
cork cambium and cork
cork and secondary cortex
cork cambium, cork and secondary cortex
In a woody dicotyledonous tree, which of the following parts will mainly consist of primary tissues?
Stem and root
All parts
Shoot tips and root tips
Flowers, fruits and leaves
Assertion : Protostele is the simplest stele.
Reason : Protostele is the most advanced type of stele.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
