Morphology of the stem - class-XI

The plant organs are classified into vegetative structures that include leaf, root, stem etc and reproductive structures like the flower, fruits and seeds 

Apical cell theory by Nageli in 1858, stated that in large number of cryptogams single solitary cell has been found to form the growing point and it was supposed that similar condition exists in higher plants too. The presence of complex growing apices in higher plants cannot be explained by this theory. 
Thus, the correct answer is option A.

Scape is the stalk of the stem that attaches the flower to its inflorescence. Onion plants produce a leafless flowering stem which exhibits scape. These have 2-4 leaves that are circular and hollow in cross-section, easily flattened when young. Whereas Torus is the thickened part of the stem from which flower grows. The older name of the torus is thalamus. Pedicel is short flower stalk that attaches the flower to inflorescence.
Thus, the correct answer is option B.

Interfascicular cambium originates from the cells of the medullary rays located between adjacent vascular bundles, becoming meristematic to form a complete ring of vascular cambium during secondary growth in stems.

The main functions of stems are as follows,

• The stems bears branches and leaves and also gives place from where flowers and fruits grow.
• Conduction of fluids and minerals between the roots and the shoots in the xylem and phloem.
• Storage of food.
• Stems have meristems that generate new living tissue.
  Thus, the correct answer is option D.
  

• An excurrent stem is the type of stem in which the main stem grows indefinitely. The side branch grows in an acropetal manner. The tree takes a pyramidal form due to development of racemose branching. This type of branching is mostly seen in pinus. This type of branching is mostly seen because the apical meristem has the dominance on the lateral ones which leads to an increase in the height of the plant.
  
• Hence in Pinus excurrent stem is found.
• So, the correct answer is  'Pinus'.

Bamboo, grass and mint stem elongate by the activity of Intercalary meristems. Intercalary meristem at base of leaves or nodes of grasses is responsible for primary growth. Meristems are classified by their location as apical located at root and shoot tips, lateral in the vascular and cork cambia, and intercalary at internodes, or stem regions between the places at which leaves attach and leaf bases. Intercalary meristem cells possess the ability to divide and produce new cells, as do apical and lateral meristems. They differ, however, in being situated between regions of mature tissue, such as at the base of grass leaves, which are themselves located on mature stem tissue.
Thus, the correct answer is option C.

Sagittaria is known for having an elongated reproductive apex, which is a specific morphological characteristic of its inflorescence development.

In some plants, the stem has been modified to perform different functions. These are the adaptations shown by the plants due to adaptation and evolution. 

Cuticle is a protecting film covering the epidermis of leaves, young shoots and other aerial plant organs without periderm. 

Erect, unbranched stems with distinct nodes and internodes are called culms, nodes are swollen giving a jointed appearance. For example, bamboo.

Cactaceae have many adaptations that make them drought resistant in dry areas. They have a thick and hard-walled stem that helps in water storage. The stems of Cactaceae are fleshy and photosynthetic. A thick and waxy coating of it helps the cactus from evaporating excess water. Instead of leaves, most of them have spines or scales which are modified leaves. These spines and scales do not lose water through evaporation and protect the cactus from herbivores.

Shoot or stem develops from plumule. Shoot or stem develops from plumule. Plumule is the future shoot of a plant as radicle is the future root of the plant. Plumule is positively phototrophic.
Thus, the correct answer is option A.

Cucurbita stem has lacunar collenchyma or tubular collenchyma which is characterized by the presence of distinct intercellular spaces and deposition of pectocellulose is on the wall of intercellular spaces. Sunflower stem has lamellar or plate collenchyma which is characterized by cell wall thickening on the tangential walls giving the cell lamellar or plates like appearance. Brinjal stem has angular collenchyma which is characterized by deposition of pectocellulose are at the angles of the cell. Maize stem has sclerenchymatous hypodermis.
Therefore, the correct answer is option A.