Plant Apex: Root and Shoot Apices

Bud is a condensed rudimentary shoot. Such buds developed into leafy shoots.

Option (B) Shoot tip transform into flower.

Accessory buds are buds that occur in addition to the main axillary bud at a leaf axil. They are essentially a type of axillary bud.

The buds found on the eyes of a potato tuber are axillary buds located in the axils of scale leaves. These buds are responsible for the vegetative propagation of the potato plant.

Even, if there is more than one tunica layer in the stem apex, only the outer layer will develop into the epidermal cells. The stem has three simple cell types, i.e. the parenchyma, collenchyma and sclerenchyma cells which are responsible for the metabolic functions, repairing and healing wounds and storing starch.

The correct option is B.

Schmidt has postulated tunica- corpus theory on the basis of studies of shoot apices of angiosperm. This theory is concerned with planes of cell division in the apex. In contrast to apical cell theory, the tunica-corpus theory is applicable only to shoot apex and not to root. There are three types of meristematic tissues like apical (at the tips), intercalary (in the middle) and third as lateral (at the sides).

Schmidt distinguished two tissue zones in the shoot apex and termed as tunica and corpus.

The correct answer is B.

Heaping soil around the base of the potato stem, known as earthing up, encourages the development of more underground stems (stolons) from the axillary buds, which then swell to form tubers.

Apical dominance is the phenomenon where the shoot apex inhibits the growth of lateral buds. The apical meristem produces auxins (IAA), which travel down and suppress the development of lateral buds closer to the apex.

The 'eye' of a potato is essentially a node where an axillary bud is present. These buds are capable of sprouting to form new plants.

A simple leaf can be differentiated from the pinnae of a compound leaf on the basis of the presence or absence of 'axillary bud'.

Actually there are generally three buds in the region of eye. Only one is axillary. The other two are accessory. 

The histogen theory was given by Hanstein (1870). The three principal tissues of the root vascular cylinder, cortex and epidermis originate from three groups of initial cells or histogens, in the apical meristem plerome, periblem and dermatogen respectively. A fourth histogen, the calyptrogen, produces the root cap.    
Thus, the correct answer is option A.    

 The formation of the root apex involves derivatives of both the basal and apical cells of the two-cell embryo, the hypophyseal region derived from the topmost cell of the suspensor is incorporated into the embryo proper, giving rise to part of the root cap.

• Promeristem is a group of young meristematic cells in its early embryonic stage from which other meristems are derived. 
  
• Apical meristems are derived from promeristem and are present below the promeristem at shoot tip and root tip.
  
• The shoot apical meristem (SAM) consists of three distinct meristematic zones called the histogens.
  
• These histogens are present at the growing tips of a stem or a root.
• These tips consist of three histogens and each of these histogens gives rise to tissues which are different from one another- dermatogen, periblem, plerome (principle tissues)
• The dermatogen or the outer layer gives rise to the epidermis, periblem or middle layer gives rise to the cortex as well as the epidermis, plerome or the inner layer gives rise to vascular tissues.
• So, the correct answer is 'Promeristem derivative destined to produce specific areas'.

Promeristem is the area of new development in a plant body where the establishment of new organs or parts of organs is started. Some of the time, it is additionally called primordial meristem, meristem and embryonic meristem.

• The quiescent centre is that part of the root-promeristems that contains the initials of epidermis, cortex and stele.
  
• These cells divide less frequently as they are inactive and are present at the pole of cortex and stele.
  
• The cells with QC have small dictyosomes, nuclei and nucleoli with little cytoplasm.
  
• These cells also have little endoplasmic reticulum, mitochondria and contain low concentrations of RNA, DNA and protein than the other cells of the root apex.
  
• So, the correct answer is 'Light cytoplasm and small nuclei'.

• The shoot apical meristem (SAM) form three distinct meristematic zones called the histogens.
  
• These histogens are present at the growing tips of a stem or a root.
  
• These tips consist of three histogens based on the type of cells they form.
• Each of these histogens gives rise to tissues which are different from one another- dermatogen, periblem, plerome (principle tissues)
  
• The dermatogen or the outer layer gives rise to the epidermis, periblem or middle layer gives rise to the cortex as well as the endodermis, plerome or the inner layer gives rise to vascular tissues.
  
• This is called histogen theory which was proposed by Hanstein in 1870.
  
• So, the correct answer is 'Type of cells they form'

A zone of inactive cells is present in the central part of the root apex called quiescent centre.

The histogen theory was given by Hanstein (1870), According to this, there are 3 groups of initials in the shoot apex. According to Hanstein, the three principal tissues of the root; vascular cylinder, cortex and epidermis originate from three groups of initial cells or histogens, in the apical meristem plerome, periblem and dermatogen respectively. A fourth histogen, the calyptrogen produces the root cap.
Therefore, the correct answer is option C.  

• The Tunica-corpus theory explains the planes of cell division in the shoot apex.
  
• It was proposed by Schmidt in 1924.
• It was proposed on the basis of the study of shoot apex.
• This theory is applicable only to shoot apex and not to root. 
  
• This theory divides the region (shoot apex) into two tissue zones known as tunica and corpus.
• The shoot apex is composed of two layers of cells of tunica and corpus  (layer L1, L2 and L3 to denote the outer layer of tunica, the inner layer of tunica and corpus respectively).
• The plasmodesmata connections exist between the cells of tunica and corpus.
• So, the correct answer is 'Shoot apex'

Calyptrogen is the specific layer of meristematic cells in the root apex that gives rise to the root cap.

According to the waiting meristem concept, the 'anneau initial' (initial ring) is the peripheral zone of the shoot apex that remains active and contributes to leaf and stem formation.

In embryogeny, the apical cell of the 2-celled embryo contributes to the embryo proper, while the basal cell contributes to the suspensor. The torpedo stage involves cotyledon emergence, and the globular stage involves the differentiation of the embryo proper.

Statement 1 is incorrect because fungal hyphae in endomycorrhizae do not bypass the Casparian strip to enter vascular tissue in that manner; rather, they typically colonize the root cortex intercellularly or intracellularly without breaching the endodermal Casparian strip directly to enter vascular tissue. Statement 2 is incorrect because the globin part of leghemoglobin is encoded by the host plant nuclear genome, while the heme group is synthesized by the bacteroid/bacterium. Thus, both statements are incorrect.

The root system forms the underground system of the plant that absorbs water from the soil along with various organic and inorganic nutrients. It exerts the root pressure due to which the absorbed water is transported to the shoot system.

Calyptrogen is the histogen responsible for forming the root cap, which is a structure unique to roots and not found in shoots.

The cells of the quiescent centre are characterised by 'light cytoplasm and small nuclei'.

Root is the most important organ of a plant which generally lies below the soil in the vascular plants.

Vascular bundles are scattered in the spongy parenchyma. These can be seen in the veins and the midrib of the leaves. The dicot leaves possess reticulate venation in which veins form a network. The xylem forms the top layer and phloem is present at the bottom in the arrangement of the vascular tissues. The veins vary in thickness in the reticulate venation.