Tag: internal structure of root, stem and leaf

Stoma (plural stomata) is a pore, found in the epidermis of leaves, stems and other organs that is used to control gas exchange. Monocots have isobilateral leaf and dicots have dorsiventral leaf. Dicotyledons usually have more stomata on the lower epidermis than the upper epidermis. Monocotyledons, on the other hand, usually have the same number of stomata on the two epidermis. In plants with floating leaves, stomata may be found only on the upper epidermis and submerged leaves may lack stomata entirely.
Thus, the correct answer is option B.

In the dorsiventral leaf or dicot leaf, mesophyll is differentiated into palisade parenchyma and spongy parenchyma. Palisade parenchyma is present on the upper side and spongy parenchyma is present on the lower side.

The region present between the upper and lower epidermises is called mesophyll. In dicot leaves, mesophyll is differentiated into upper palisade parenchyma and lower spongy parenchyma. It is found in dicot leaves.

So, the correct answer is ‘Dicot leaves’

In dorsiventral leaf, more number of stomata occur on lower epidermis and less number of stomata present on upper epidermis.

So, the correct option is ‘occur on lower epidermis'.

in dorsiventral or dicot leaf, midirib or main vein represents the vascular bundles. In this, xylem is present towards upper epidermis and phloem present towards the lower epidermis. These are collateral, conjoint, closed the position of protoxylem and metaxylem is not specified clearly.

So, the correct answer is 'Adaxial and abaxial respectively'.

In dorsiventral leaves, less stomata are present in the upper epidermis and more stomata are present on the lower epidermis.

So, the correct option is ‘Fewer on upper surface and more on lower surface’.

Stele with four vascular bundles is called tetrarch stele. it is generally found in dicotyledons. In the vascular bundles xylem and phloem are on different raidii. So the vascular bundles are called radial vascular bundles. In the xylem protoxylem is faced towards the pericycle and metaxylem is faced towards the medulla.  eg:Cicer arietinum  roots. 

Xylem comprises of vessels, tracheids, xylem parenchyma, and restricted xylem strands.  the vessel is Y-molded with bigger two round set metaxylem vessels shaping the arms and littler yearly or winding protoxylem vessels, framing the base.

Every year one spring ring and one autumn rings make one annual ring which is used to estimate the age of the plant.

The semilunar valves are present inbetween the aorta and the left ventricle (aortic semilunar valve) and between the right ventricle and the pulmonary artery (pulmonary semilunar valve). The aortic semilunar valve functions to pevent backflow of blood into the ventricle. Damage to chordae tendinae of the aortic semilunar valve will therefore cause backflow of blood to the left ventricle. The first heart sound is produced by the closure of the mitral and the tricuspid valve, that are the atrioventricular valves.