Anatomy of Flowering Plants Test - 79

Passage cells are endodermal cells of older roots, which have retained thin walls and Casparian strips rather than becoming suberized and waterproof like the other cells around them, to continue to allow some symplastic flow to the inside. 

After the process of abscission of leaf, the tissue at the scar is exposed to the air. To protect these tissues from desiccation and infection a protective layer of cells is formed. This layer is either developed by the suberization of already existing parenchyma cells (primary protective layer) or by a typical periderm (secondary protective layer). So, the correct option is D.

Secondary meristem develops from permanent tissues during secondary growth and gives rise to secondary tissues. Cork cambium is the secondary meristem. It is found in many vascular plants. It is a part of periderm. The cork cambium is involved in the secondary growth in the plant. 
Thus, the correct answer is option C.

Cork is an impermeable, buoyant material, a prime-subset of bark tissue that is harvested for commercial use primarily from Quercus suber. Cork is composed of suberin, a hydrophobic substance and because of its impermeable, buoyant, elastic and fire retardant properties, it is used in a variety of products, the most common of which is for wine stoppers. 
Therefore, the correct answer is option D.

Plate meristem divides in two planes at right angle to each other. Such growth results in a flat plate of tissue. These meristems are found in uniseriate epidermis and multiseriate flat blade of leaf. 
Therefore, the correct answer is option A.

• Dicot root vascular bundles are described as radial. There are 2 to 6 bundles each of xylem and phloem occurring alternately. Xylem is described as exarch. 
• Monocot root vascular bundles are radial in the arrangement. There are eight bundles each of xylem and phloem. Hence, the condition is described as polyarch. Xylem is described as exarch. 

So, the correct answer is option D.

Lenticels originate beneath stomata, simultaneous with the initiation of the first layer or periderm or just before the initiation of periderm, during first growing season. As the lenticels formation starts, the parenchyma cells found near substomatal cavity lose their chlorophyll content and irregularly divide in different plants giving rise to a mass of colourless, rounded, thin walled, loosely arranged cells called as complementary cells. 
Some times complementary cells produced by phellogen towards outside instead of producing cork cells. As the complementary cells increase in number, pressure is exerted against the epidermis and it ruptures. Outer most cells gradually become dead and may replaced by cork cells. Beneath the outer layer some mass of closely packed cells alternate to loosely arranged cells are formed called as closing layer. From inner side continuous production of complementary cells cause rupture of closing layer at intervals. So, lenticels and its complementary cells are developed through the activity of phellogen and not of steler cambium, dermatogen and intercalary meristem. 
Therefore, the correct answer is option A.

Knots are common blemishes in trees, often causing lumps or holes within the trunk of the tree itself. In most cases knots are caused by the natural growth of the tree, though the specific circumstances under which they form determines how they will appear. As a tree grows and increases the circumference of its trunk, the growing trunk begins to overtake the branches that grow out from it. Knots form around these branches, building up trunk material as the tree continues to expand. Since, the branches are still growing as they are overtaken by the trunk, the knot that forms is solid and contains living wood throughout. The wood of the knot is typically tougher than the surrounding wood and may form a bulge around the branch emerging from its center. So, knots are formed in wood due to bases of the branches get buried in main stem and not because leaf scars, insect bites and injuries. 
Therefore, the correct answer is option B.

The vascular cambium is located between the xylem and the phloem in the stem and root of a vascular plant and is the source of both the secondary xylem growth and the secondary phloem growth. 

Date palm is a monocot and lack lateral meristem; the meristem present along the sides causing the increase in girth of the plant.