Morphology of leaf - class-XI

The leaves of the plant possess the mesophyll tissue which contains the cellular organelle chloroplast. This organelle contains the chlorophyll pigments which are responsible for the absorption of light and conversion of this energy to synthesize food by the process of photosynthesis. 

In spinach, leaves have modified functions. They are modified to store food and water. They store their food in leaves. So, leaves of spinach are a rich source of nutrition and are frequently consumed. 

Amphistomatic: A leaf is said to be called as amphistomatic when the stomata are present on both the side of the leaf.

A simple leaf has a single leaf blade or lamina inserted into the petiole. It may have incisions but these incisions do not divide the blade into leaflets. It shows the presence of an axillary bud at its axil. For example mango. 

When white light is incident on an object , it absorbs some constituent colours of white light and some are reflected back , the combination of reflected colours decides the colour of an object that we see. 

Amphistomatic: A leaf is said to be called as amphistomatic when the stomata is present on both the side of leaf.

Amphistomatic: A leaf is said to be called as amphistomatic when the stomata are present on both the side of the leaf.

Stomata are the openings surrounded by the guard cells, present in the epidermis of the leaves. It helps in the gaseous exchange in plants. The position of guard cells varies in different plants on the basis of climate. They are found in cavities, called stomatal crypts in Nerium oleander (non-succulent xerophyte). They are sunken (lower the epidermis) in xerophytic plants to recuce the water loss. They are found in grooves in Ericales lined with epidermal hair. So, the correct answer is 'Stomatal crypts'.

The large, bubble-shaped epidermal cells that occur on the upper surface of the leaves of monocots are called as bulliform cells. They are also called as motor cells. They help in the unfolding of developing leaves. It involves in the rolling and unrolling of mature leaves in response to alternating wet and dry periods.

Palisade parenchyma is found immediately below the upper epidermis. It is 2 to 3 layered, with compactly arranged tubular cells, rich in parietal chloroplasts. The adaxial surface is the upper surface of a leaf. The abaxial surface is the lower surface of a leaf.

Epistomatic stomata is having stomata on the upper surface of the leaf. This type of stomata is mostly found in aquatic plants. Aquatic plants float on the surface of the water and therefore stomata are not found in the lower epidermis. Stomata are found on the upper epidermis because for direct exchange of gases between the leaf and the atmosphere. 

Bulliform cells are found in the axial or upper surface of the epidermis of monocots. These are large, colourless, bubble-shaped (empty) cells found in clusters near the mid vein. In the presence of insufficient water, these cells loose water and become flaccid. In response to this condition, the leaf rolls inward (to expose the minimum part of the leaf) to minimise the water loss. So, the correct 'Bulliform cells'.

The cuticle is comprised of polymers of wax. This layer is present on the surface of the epidermis of leaf and stem. This is the waxy and waterproof layer. This layer prevents the loss of water from the leaves and stem. This protective layer allows the retention of the water. This helps to reduce the loss of water in the form of water vapour by transpiration. 

Relative growth is the increase in size relative to the size of the plant leaf present at the start of a given time interval. It can be also expressed as percentage increase.

Phyllode is a green, expanded structure formed by the modification of petiole or rachis of the leaf. In most of the xerophytes, leaves are reduced to prevent water loss in such plants phyllodes develop to carry out photosynthesis.

A swelling at the base of a petiole is known as pulvinus. It is a joint-like thickening at the base of a plant leaf or leaflet that facilitates growth-independent movement. For example, mango, pea and gram.
Therefore, the correct answer is option B.

Leaves develop from nodes. Apart from leaves, branches and aerial roots also develop from nodes from the stem. It also holds buds. Adventitious roots may also develop from it. Internodes are the intervals between the nodes. 

The few epidermal cells surrounding the guard cells are modified to act as subsidiary cells. They lack chloroplasts and help in functioning of the guard cells by maintaining the water and solute balance with the guard cells.

Leaves are exogenous (develop away from the plant body) in origin and develops from the swollen leaf primordium of the growing apex.

• Guard cells are specialized epidermal cells present on the surface of leaves and stems of plants that control the gaseous exchange in plants.
• The guard cells form stomatal pores through which gaseous exchange and transpiration take place.
• In monocots, the guard cells are dumbbell shape.
• In dicots, they are kidney or bean shaped.
• So, the correct answer is 'Beans'.

Stomata are the openings surrounded by the guard cells that are specialized epidermal cells. These are present on the underside of the leaves and perform the functions of exchange of gases and transpiration.

Broad part of leaf is lamina. The lamina is the expanded portion of a leaf and it is specialized for photosynthesis. For this purpose, a leaf is typically flat and thin, to expose the chlorenchyma to light over a broad area and to allow light to penetrate fully into the tissues. 
Thus, the correct answer is option C.

Exogenous, flattened, green, lateral appendages arising from nodes of the stem or branches in acropetal succession are called as leaves. Leaves arise from shoot apical meristem and bear buds in their axils and help in assimilation of food, exchange of gases and transpiration. So, leaf is a lateral outgrowth of stem.  

• Node: The leaves arise in the regions of the plant known as the plant nodes and are therefore the point of attachment of the leaves. 
• The region of the plant between two nodes is known as the internode.
•  The angle between the upper surface of the leaf and the stem from which it arises is known as the axil. 
• The petiole is the stalk which attaches the leaf to the stem. 

leaf is a green outgrowth of a stem. It performs photosynthesis and provides food to the rest of the plant body. There are different types of leaves found due to climate, water availability, etc. A leaf consists of lamina and petiole, leaves can be monocot or dicot. It contains stomate which helps in gaseous exchange.

Marginal meristem is the meristem located along the margin of a leaf primordium and forming the leaf blade. The apical meristem or growing tip, is a completely undifferentiated meristematic tissue found in the buds and growing tips of roots in plants.
Intercalary meristems are capable of cell division, and they allow for rapid growth and regrowth of many monocots. Intercalary meristems at the nodes of bamboo allow for rapid stem elongation, while those at the base of most grass leaf blades allow damaged leaves to rapidly regrow.
In mass meristem the cells divide in all planes to form bulk of tissue. this type of meristem takes part in the formation of cortex, pith, endosperm and sporangia.
Therefore, the correct answer is option D.

A hydathode is a type of secretory tissue in leaves, usually found in angiosperms, that secretes water through pores in the epidermis or margin of leaves, typically at the tip of a marginal tooth or serration. 

• A leaf is said to be hypostomatous where stomata are present on abaxial surface only (lower surface). Most tree species of dicotyledons possess such leaves. Ex. Ficus, Nerium etc.
• Hypostomatous plants are non-aquatic plants in which stomata are present on the lower surface because their function is to regulate the amount of water in the leaf and being on the bottom prevents it from absorbing too much water in the rain or transpirating too much in the sun.

Palisade tissues are present just beneath the epidermis and are composed of elongated cells arranged parallel to each other in one to three layers. These cells are marked by the presence of abundant chloroplast and thus provide the site for photosynthesis. Loosely arranged irregular cells with large intercellular spaces make the spongy parenchyma, which is present just beneath the palisade tissue. They contain less chloroplast as compared to that of palisade tissue. Thus, the correct answer is option A.

Plants have three types of meristems, the apical meristem, the intercalary meristem and the lateral meristem. Leaves are derived from shoot apical meristem which swells to form undifferentiated leaf primordium which divides into two systems that develop leaf blades and leaf sheaths. The growth of leaf blades occurs due to cells division but is mainly from cell elongation. The flattened blade form is derived from the marginal meristem present at the margins of leaf axis. Meristem present at the sides and causes increase in girth of the plant is termed as lateral meristem and is not involved in leaf formation.
Therefore, the correct answer is option C.

If the veins on the the leaf run parallel to each other throughout the leaf, it is known as parallel venation. It is a feature of monocotyledonous plant. This type of veins are found in grasses.

Plant with single leaf, Monophyllea (angiosperm) plant with two leaves only Welwitschia (gymnosperm).

A ligule is an outgrowth present at the junction of leaf sheath and lamina in grass leaf. It occurs at the end of petiole at the leaf base. It is a strap-shaped extension of the corolla. It is a membranous appendages. Grass leaf also has sheathing leaf base. 

Petiole is a stalk that attaches a leaf to the stem of a plant. A leaf without petiole is called as sessile leaf. It is a transition between the stem and the lamina.

The smallest leaf occurs in Wolffia. In Wolffia, the leaf is fused with the stem to form minute flat thallus. Thus, the correct answer is 'Wolffia.'

A. Spongy tissue – parenchyma with less number of chloroplast.

B. Palisade tissue – parenchyma with more number of chloroplast.

C. Guard tissue – modified epidermal cells with chloroplast, present in the stomata.

D. Bundle sheath – Thick walled parenchymatous sheath present around the vascular bundles in leaves.

So, the correct option is ‘Palisade tissue’.

The foliage leaf consists of three parts, namely leaf base, petiole and lamina. The leaf base is also called as hypopodium. The petiole part of the leaf is also called as mesopodium. The lamina part of the leaf is called as epipodium.

Winged petiole is the petiole in which there is a thin flange of tissue along the length of the petiole. It is a green flattened petiole. Plants like Citrus and Dionaea possess winged petiole. Thus, the correct answer is 'Citrus.'

The largest leaf belongs to Victoria regia in plant kingdom. The approximate diameter of Victoria leaf is 1.3 meter. It is an aquatic plant. It has a floating leaves. 

In grasses and many monocots, the leaf base (petiole) is broad and surrounds the stem as an envelope. Such a leaf base is known as sheathing leaf base. In grasses such as wheat, maize and grass, the sheathing leaf base protects the intercalary meristem. Hence, the plants belonging to family Poaceae have sheathing leaf base.

• Minerals crystals are found in plant cell walls in the form of calcium oxalate, carbonate or silica.
  
• Silicon is found on the leaf surface in the form of spines and other sharp bodies which are known as phytoliths.
  
• It makes the grasses abrasive and foliage indigestible to organisms feeding on them (herbivores).
• Silica incrustation is the deposition of silicon on the leaf surface, it is a defence mechanism found in closely related species of grasses which makes its leaves abrasive.
• So, the correct answer is 'Grasses'.

• Plastochron is the time interval between the two successive events during the growth of plants.
  
• As in the case, when the shoot tip of a plant grows new leaves are produced at regular time intervals.
• This time interval between the beginning of leaf growth at 2 consecutive nodes in a growing shoot apex by keeping the temperature constant is called Plastochron.
• So, the correct answer is 'Period between two successive leaf primordia'

Veins have vascular tissues xylem and phloem. Xylem fulfills the requirement of water of the leaves. Phloem transport food energy to the leaves. They also provide support for the leaf.

• Minerals crystals are found in plant cell walls in the form of calcium oxalate, carbonate or silica.
  
• Cystoliths refers to the deposition of calcium carbonate in the epidermal cells of leaves of the plants belonging to the genus Acanthaceae and Urticaceae (stinging nettles).
• So, the correct answer is 'Cystoliths'.

• A leaf base is also known as hyphopodium, it is the lowermost part of the leaf which is slightly expanded region where the leaf get attached to the stem.
  
• It is indistinct in most of the plants which act as a cushion for the leaves.
• The vegetative shoot apex consists of two regions i.e, summit and flank.

1. Summit-  The rate of division is slow and it is located at the apex.
   
2. Flank- The rate of division is very fast and it lies behind the summit.
   

• Leaf primordium is formed on the flanks by the flank meristem.
  
• So, the correct answer is 'Leaf base'

In an unifacial leaf, the stomata are present in lower and upper epidermis. Unifacial leaf is also called as isobilateral or amphistomatic. Unifacial leaf is a leaf that develops from one side of the leaf primordium only and in consequence has only an encircling adaxial or abaxial epidermis (may be secondarily flattened and appear dorsiventral).
Thus, the correct answer is option C.

Stoma (plural stomata) is a pore, found in the epidermis of leaves, stems and other organs that is used to control gas exchange. The pore is bordered by a pair of specialized parenchyma cells known as guard cells that are responsible for regulating the size of the opening.
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. 

A leaf which possesses stomata exclusively its upper side is called as lotus type. Aquatic plants are plants that have adapted to living in aquatic environments. They are also referred to as hydrophytes or macrophytes. These plants require special adaptations for living submerged in water or at the water's surface. The most common adaptation is aerenchyma, but floating leaves and finely dissected leaves are also common.
Thus, the correct answer is option C.

There are different types of stipules present in plants such as lateral, ventral, scaly, intrapetiolar, interpetiolar, ochreate, spinous, tendrillar. In ochreate, the stipules are in the form of a tubular sheath around the internode. These are seen in leafy vegetables like Rumex and Polygonum. Foliaceous stipules occur in Lathyrus aphaca. Tendrillar stipules occur in Smilax. Thus, the correct answer is 'Rumex.

In peltate leaf, the leaf blades are deeply lobed. In this, the petiole is attached to the middle of the adaxial side of the leaf. Examples of leaves having peltate leaf blade include Nelumbium, Victoria, Tropaeolum. In this, the petiole is attached to the surface of lamina. Thus, the correct answer is 'Peltate.'

A swollen leaf base is called as Pulvinus. This type of leaves are seen in Fabaceae family. The swelling results due to change in the turgor pressure. Night closure movement of legume leaves shows this pulvinar movement. The pulvinus protects the young axillary bud.

Pulvinus is a swollen leaf base. Pulvinate leaf base is found in leguminous plants. It is seen in mango leaves. It is seen in Fabaceae family. Example includes Trifolium pratense.

Compound leaves are of two types, namely pinnately compound leaves and palmately compound leaves. In palmately compound leaf, the leaflets are arranged at the tip of the petiole. It is further divided into 5 types depending upon the number of leaflets present at the tip of the petiole. In unifoliate, there is only one terminal leaflet is attached at the top of petiole. Example includes Citrus. In bifoliate, two leaflets are attached side by side at the terminal end of petiole. Example includes Balanites roxburghii. In trifoliate, three terminal leaflets are attached at the terminal end of petiole. Example includes Aegle marmelos. In quadrifoliate, four leaflets are attached to the tip of petiole. Example includes Paris quadrifolia. In multifoliate, five or more leaflets are present at the tip of petiole in the form of fingers of the palm. Example includes Bombax malabarica.

A ligule is a variously modified extension of the sheath lying at the
base of the blade. While this vegetative part of the leaf blade of the family of grasses, is often a vertical membrane present as an outgrowth at the inner junction of the leaf sheath and blade, in heterosporus lycophytes, this is one of the enigmatic structures. The term which means a little tongue is an appendage that is found at the adaxial side of the leaves. Found in mostly Selaginellales and Isoeteles, the mature ligule shows four regions, sheath, glossopodium, main body and apex. The sheath is the base of the ligule which is composed of long tube shaped cells. The glossopodium is found just above the sheath as vaculoted cells.
Therefore, the correct option is A.

Leaves, in which stomata are present on the upper epidermis are called epistomatic leaves. In Nympheae, Nelumbo, Victoria, epistomatic leaves are present.

So, the correct option is ‘All of the above’.

The function of the stomata is to allow water vapor and gases to pass in and out of the leaf. The stomata are also responsible for the process of transpiration, the rate at which a plant loses water. Air enters the plant through the stomata. The air contains carbon dioxide which is used in the photosynthesis process. Then the transpiration and photosynthesis are the main functions of leaves.

Hydrophytes, in which root system is rooted in the soil and their leaves float on the surface of water. In these leaves, stomata are present on the upper epidermis or surface. Such leaves are called Epistomatous leaves. Eg:Nelumbo, Nympheae.

So, the correct option is ‘Upper surface’.

In the vascular bundles of leaves, xylem is situated towards the adaxial or upper epidermis side and phloem is situated towards the abaxial or lower epidermis side.

So, the correct option is ‘lower epidermis’.

The main function of leaf is photosynthesis. It produces food for the plant. It has a photosynthetic pigment chlorophyll which converts solar energy into chemical energy. The leaf is also involved in the transpiration process. The transpiration process helps in cooling of plant. The exchanges of gases takes place through stomata present on the leaves.