Lecture 8 - Plant Anatomy PDF

Lecture 8 –permanent tissues BOT1131: Plant Anatomy 27.11.2024, 8-9 AM  Collenchyma Tissues Collenchyma is a simple, permanent tissue typically found in the shoots and leaves of plants. Collenchyma cell walls are thickened with cellulose. Due to the thickened corne...

Lecture 8 –permanent tissues BOT1131: Plant Anatomy 27.11.2024, 8-9 AM  Collenchyma Tissues Collenchyma is a simple, permanent tissue typically found in the shoots and leaves of plants. Collenchyma cell walls are thickened with cellulose. Due to the thickened corners, this tissue provides strength, particularly in growing shoots and leaves. The cells are tightly packed and have fewer intercellular spaces. Characteristics of Collenchyma It is typically located between the cortex of the stem and the endodermis of its vascular bundles. Characteristics of Collenchyma Collenchyma consists of living cells. Shapes of the cells are elongated, oval, spherical, or polygonal. Collenchyma cells contain an unevenly thickened primary cell wall. Characteristics of Collenchyma The intercellular spaces are small. Collenchyma can expand radially and tangentially on absorbing water due to their weak lignified cell walls. It contains chloroplasts for food storage. During the secondary growth of the plant, collenchyma tissues get crushed. Based on the thickening of the cell wall, collenchyma is divided into 4 types: Corner uniformly thickened continuous layers thickening are more of thickening around intercellular spaces  Lacunar Collenchyma: Lacunar Collenchyma contains intercellular spaces, and thickening is more around these spaces. Cucurbita Angular Collenchyma: In this type, the thickening occurs at the corners of the cells, giving them a distinct angular appearance. It is the most common collenchyma tissue. Cucurbita Annular collenchyma: In annular collenchyma, the cell wall is uniformly thickened. Carrot plants, Nerium Lamellar Collenchyma: Lamellar Collenchyma cells have continuous layers of thickening in their cell walls. The cell walls are unevenly thickened, with the thickest regions forming these layers. Collenchyma Structure Function Cells are spherical, oval or This allows for close packing to polygonal in shape with no or little provide structural support. intercellular spaces. Corners of cell wall are thickened, Provides mechanical strength. with cellulose and pectin deposits. Cells are thin-walled on most Provides flexibility, sides. allowing plant to bend in the wind.  Functions of collenchyma tissues Collenchyma cells provide structural support, protecting the plant by serving as an inner framework, much like bones do for humans and other animals. Plants are exposed to numerous structural challenges and without these cells, most plants would be too fragile to withstand the damage caused by heavy rains, high winds, and other stresses. The thickened walls of the collenchyma cells enable them to provide additional support to the areas where they are found. Most notably, collenchyma cells serve growing parts of the plant, such as shoots and leaves, both by providing support and by filling in vacant spaces that will be used for later growth.