Anatomy of Flowering Plants Test - 22

Pith or medulla, is a tissue in the stems of vascular plants. Pith is composed of soft, spongy parenchyma cells, which store and transport nutrients throughout the plant. In dicots, pith is located in the centre of the stem. In monocots, it extends also into flowering stems and roots. The pith is encircled by a ring of xylem. The xylem, in turn, is encircled by a ring of phloem. The monocot root has a pith, whereas the dicot root does not. Absence of pith is the diagnostic feature of dicot root. Pith is present in dicot stem, monocot stem, monocot root and dicot stem. 
Thus, the correct answer is option D.

Parenchymatous cells are thin walled polyhedral, isodiametric living cells with sufficient cytoplasm and one or more nuclei. Collenchymatous cells have thick non lignified walls that provide mechanical support and tensile strength to the growing organs. Sclerenchymatous cell are thick walled dead lignified cells without any secretory function; these cells together with collenchyma makes major part of mechanical tissues of plant. Cell with ability to produce new cells are said to have meristematic activity and are termed as meristematic cells. Maize stem has single layered epidermis which is covered with well developed cuticle. It is followed by sclerenchymatous hypodermis which is 5-7 layers thick outer cortical region which in turn surrounds aerenchymatous ground tissues. 
Therefore, the correct answer is option C.

The ground tissues in dicot stem are well differentiated into cortex, endodermis, pericycle and pith but are undifferentiated in monocot stem. Dicot stem has pith with thin walled parenchymatous cells but monocot stem lacks it. Primary dicot root has no or reduced pith, whereas a large pith, sometimes sclerenchymatous, is present in the monocot root.
Therefore, the correct answer is option A.

Pericycle is a primary tissue of plant roots and is the site for the initiation of lateral roots and two secondary meristems, the vascular cambium and cork cambium (phellogen). 

Cortex is the ground tissue present between epidermis and endodermis. It is mostly composed of parenchymatous cells. Parenchymatous cells are thin walled polyhedral, isodiametric living cells with sufficient cytoplasm, one or more nuclei and nucleolus. They serve to store food. Chlorophyll is present in chlorenchyma which are specialized to perform photosynthesis and are present in leaves. Thus, the correct answer is option A.

Hard bast is the patch of sclerenchyma present on outside of each vascular bundle, thereby forming a bundle cap over each bundle. They serve to provide additional mechanical support to the stem and are present in Sunflower stem. Wheat stem represent a monocot stem in which each vascular bundle is surrounded by thick walled bundle sheath, they do not have hard bust. Root is marked by presence of primary xylem and phloem in different radii, separated from each other.
Therefore, the correct answer is option A.

As we know that Intrafascicular or intrastelar cambium is present between xylem and phloem in dicot stem and roots. Pith rays, present between the edges of intrafascicular cambium, divide to form a new cambium strip between the two vascular bundle i.e. interfascicular cambium. Thus, inter and intra fascicular cambium together forms a complete cambium ring called as vascular cambium or just cambium which forms secondary xylem on inner side and secondary phloem on outer side. Differential cambial activity during autumn and spring season result in narrow and wide secondary xylem rings respectively which together forms the annual growth ring. Thus annual growth ring is derived from vascular cambium which is derived from inter and intrastelar cambium.

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 formation of more than one annual ring. These are called as pseudo annual rings. So, sea shore trees do not show annual rings because there is little climatic variations and not because, they belong to monocots, there is enough moisture or soil is sandy.
Therefore, the correct answer is option A.

Phellogen is the extrastelar lateral meristem that produces extrasteler secondary tissue system. Epidermis is the outermost covering of the primary stem that delimits cotex on outer side and is ruptured by stelar secondary growth, therefore cannot produce phellogen. Cortex is the ground tissue which surrounds the central stele and is derived from ground meristem. Hypodermis refers to 5-7 layers of cortical cells present just beneath the epidermis which resume the meristematic activity and produce phellogen just beneath the epidermis. The innermost layer of cortex forms endodermis while the phellogen is produced just beneath the epidermis. The outermost covering of stele forms pericycle it is an intrasteler tissues present in a stele which means that phellogen (extrastelar lateral meristem) cannot be produced by pericycle. The phellogen or cork cambium produces cork or phellem towards the periphery. 
Therefore, the correct answer is option A.

Vascular cambium is a lateral cambium which is produced by intrafascicular (present between xylem and phloem) and interfascicular cambium. Vascular cambium adds phloem or xylem mother cell that differentiates into their respective cell types, thus, it causes secondary stellar growth. Hypodermis, the cortical cells present just beneath the epidermis, resume the meristematic activity and produce phellogen just beneath the epidermis. Phellogen is the extrastelar lateral meristem that produces extrasteler secondary tissue system. The cork cambium or phellogen produces phelloderm on inside and phellem or cork on outside thereby adding extrastelar secondary tissues.
Therefore, the correct answer is option B.