Question

1) List 5 adaptations that allow plants to live in relatively dry conditions. What is the order in which these evolved?

2) List two of the earliest adaptations plants developed to live on dry land. Why were these first adaptations, coming before vascular tissue, roots, or leaves?

Answer 1

1) Adaptations that allow plants live in relatively dry conditions include,

• Presence of cuticle which is thick and waxy, inorder to avoid the loss of water from plant.
• Plants pocess lesser number of stomata as stomata is involved in loss of water through leaves (transpiration). These stomata can be also found in sunken pits.
• In addition, the stomata will be closed during the day time, where there can be excess loss of water and instead it opens during the night time.
• The leaves are usually reduced to spines (eg: cacti) inorder to reduce their surface area to volume ratio.
• Plants pocess both deep roots and shallow roots. Deep roots are to babsorb maximum of underground water availabe and shallow roots which spreads helps in getting water from occassional rainfall.

2) Presence of rhizoids and Falcate and Secund leaf.

Water absorbtion through the leaf like gametophyte.

In the evolutionary history of plants Non vascular plants were followed by vascular plants. Non vascular plants doesnot posess vascular tissues like Xylem and Phloem for tansport. They doesnot pocess true stem, leaves or roots. So, these plante are closely associated with moist habitats. However, in order to survive water stress, they have Falcate and secund leafs where the leaves are turned to one side and strongly curved. Rhizoids have role with structural support. These plants absorb water through leaf like gametophyte.

Since vascular plants that pocessed vascular tissue evolved later, the non vascular plants pocessed these adaptions to overcome water stress.