Anatomy of Flowering Plants Test - 83

The periderm is the secondary protective (dermal) tissue that replaces the epidermis during growth in thickness of stems and roots of gymnosperms and dicotyledons (i.e., secondary growth). 

Intrafascicular cambium is present between xylem and phloem in dicot stem and roots. It is also termed as fascicular cambium. This meristematic area spreads laterally from each bundle and eventually becomes continuous, forming a complete vascular cambium.

• 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. 
• Monocot stem vascular bundles are numerous in number and the xylem is endarch. 
• Dicot stem vascular bundles are eight in number, arranged in form of a broken ring. The vascular bundles are conjoint, collateral, and open. Xylem is on the inner surface and phloem on the outer surface. Xylem is described as endarch. 
• Dicot root vascular bundles are described as radial and tetrarch. There are four bundles each of xylem and phloem occurring alternately. Xylem is described as exarch. 

So, the correct answer is option B.

Dicot root vascular bundles are described as radial and tetrarch. There are four bundles each of xylem and phloem occurring alternately. Xylem is described as exarch. Pith is absent in older dicot roots. Vascular bundles are four in number. Thus, option D is correct.

More distinct annual rings are formed in that regions where climatic variations are sharp. More distinct annual rings are formed in temperate plants. Distinct annual rings are not formed in tropical plants. Distinct annual rings are not formed in India except, Himalayan regions. Least distinct annual rings are formed in seashore regions because the climate remains same throughout the year. More clear annual rings are formed in deciduous plants as compared to evergreen plants. In deserts, annual rings are less distinct. Annual rings are bands of secondary xylem and xylem rays. Sometimes drought conditions prevail during the middle of a growing season resulting in the formation of more than one annual ring. These are called as pseudo-annual rings. 

Endarch is the arrangement in which the protoxylem is directed towards the centre and metaxylem elements towards the periphery. The development of the xylems in this arrangement follows the centrifugal pattern. It is the characteristics of the stem of flowering plants.

Whereas exarch is the arrangement in which the protoxylem is directed towards the periphery and metaxylem towards the centre. The development of the xylem in this arrangement follows the centripetal pattern. It is the characteristics of roots.

Cork tissue is also known as phellem. Cork cells are dead when mature and hence form the outer layer in stems and roots of woody plants. They are impermeable to water and gases. 

Intrafascicular cambium is present between xylem and phloem in dicot stem. It is also termed as fascicular cambium. This meristematic area spreads laterally from each bundle and eventually becomes continuous, forming a complete vascular cambium.

Interxylary phloem is found in Calotropis stem. It is said to be interxylary due to its presence inside xylem. It is also found in same member of family of Solanceae.