Bachelor’s Degree Programme (BSCG) – Plant Anatomy and Embryology Assig. Answer | BBYCT – 135 (Q-2)
2. a) Explain different types of meristems found in plants with the help of a well labelled diagram.
b) Enumerate the major features of Tunica Corpus Theory of shootapical organization.
a) The meristem is divided into three types on the basis of the positions – apical meristem, intercalary meristem and lateral meristem.
(i) Apical meristem is found at the tips of roots, stem and branches. It is responsible for the increase in the length of the plant. It is divided into three zones-protoderm, procambium and ground meristem. Protoderm gives rise to epidermal tissue, procambium gives rise to primary vascular tissues and ground meristem gives rise to cortex and pith.
(ii) Intercalary meristem is present in the nodal region and is prominently found in monocotyledons, e.g grasses. As the name indicates, it is present in between the permanent tissues. It is derived from the apical meristem and is responsible for the elongation of internodes.
(iii) The meristem that is present along the longitudinal axis of stem and root is called lateral meristem. Vascular cambium and cork cambium are examples for lateral meristem. It produces secondary permanent tissues which result in the thickening of stem and root.
b) The Tunica corpus theory was proposed by ‘Schmidt’ in 1924. This theory is relevant only to shoot apex. It is based on the plane of division of cells. According to this theory, the shoot apex consists of two distinct layers, namely, Tunica and Corpus.
-Tunica: i) It is single-layered and creates epidermis. The cells of tunica are smaller as compared to corpus and divided by anticlinal divisions mostly.
ii)Tunica forms a protoderm which gives rise to the sterna and leaves the epidermis.
-Corpus: i) It represents the central core with larger cells. The cells divide into all planes (anticlinal and periclinal).
ii) Corpus is the inner mass that splits to create procambium and terrestrial meristem.