Thick cuticle on leaves are typical of plants growing in
Wet habitats
Warm habitats
Dry habitats
Cool habitats
Histogens are component of or The histogens are differentiated in
In which of the following, there is no differentiation of bark, sap wood and heart wood
$A$ : Complementary cells are cut-off by phellogen towards outside.
$R$ : Phellogen is partially secondary in origin.
Phloem parenchyma is absent in
Wilting of plants takes place when one of the following takes place