Test: Secondary Growth- 1

30 Questions MCQ Test Botany for Class 11 - Notes and Tests | Test: Secondary Growth- 1

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Which will decay faster if exposed freely to the air


Sapwood is the younger and outermost wood. It is living wood and its principal functions are to conduct water from the roots to the leaves and to store the reserves. However, by the time they become competent to conduct water, all xylem tracheids and vessels have lost their cytoplasm and the cells are therefore functionally dead. All wood in a tree is first formed as sapwood. They can be decayed faster if freely exposed to air. Heartwood is made up of dead cells and hence is not destroyed easily.
Thus, the correct answer is option B.


Periderm is formed from -

Solution: Periderm—the Outer Defense Layer. The first defense line in conifer stems is the outer surface of the bark, the periderm. Inside the periderm is the cork cambium (or phellogen), a secondary meristem that produces cork tissue (phellem) outwards and secondary cortex (phelloderm) inwards.so option B.

Abnormal secondary growth is observed in -

Solution: Dracaena is a genus of about 120 species of trees and succulent shrubs. In the APG IV classification system, it is placed in the family Asparagaceae, subfamily Nolinoideae. It has also formerly been separated into the family Dracaenaceae or placed in the Agavaceae.

Statement–1 : The heart wood is more durable and resistant to the attack of the micro organisms and insects as compared to the sap wood.

Statement–2 : The heart wood contains organic compounds like oils, aromatic substances, gums, resin, tannins and phenol etc.


Heart wood of most of the woody trees, fails to conduct sap due to the obstruction by ?


Heart wood of most of the woody trees, fails to conduct sap due to the obstruction by tyloses. Tyloses are found in secondary xylem. They are outgrowths on parenchyma cells of xylem vessels. When the plant is stressed by drought or infection, tyloses will fall from the sides of the cells and dam up the vascular tissue to prevent further damage to the plant. Tyloses can aid in the process of making sapwood into heartwood in some hardwood trees, especially in trees with larger vessels. These blockages can be used in addition to gum plugs as soon as vessels become filled with air bubbles and they help to form a stronger heartwood by slowing the progress of rot.


Dendrochronology is the study of -


Noting the similarity in the response of trees across the region, he invented a technique that would prove to be a fundamental tool in tree-rings studies: cross-datingis a technique that ensures each individual tree ring is assigned its exact year of formation by matching patterns of wide and narrow rings between cores.


A timber merchant told his customer that log of wood which he was purchasing comes from a 20 years old tree, he told so by inspecting the -


Growth rings provide knowledge plant age .two growth rings formed in one year,one in spring season and one in winter season.


Commercial cork is obtained from :-


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.


Annual rings are well demarcated in trees growing in -


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, annual rings are well demarcated in trees growing in Shimla compared to Bombay, Delhi, Madras and Udaipur, because of sharp climate changes.


The trees growing in deserts will -

Diameter Growth. Each year, the tree forms new cells, arranged in concentric circles called annual rings or annual growth rings. These annual rings show the amount of wood produced during one growing season. At first, the cambium produces numerous large cells with thin walls that form the springwood (earlywood).


Protective layer found at the site of abscission is

Solution: In the area where the petiole of the leaf joins the twig, theres an abscission zone made up of two kinds of tissue the abscission layer and the protective layer. The protective layer is closest to the twig. The abscission layer is between the protective layer and the petiole. Both of these layers are only a few cells thick. During the growing season this layer of cells is healthy and keeps the leaves attached to the tree. But when the days become shorter, things begin to change in this zone. The protective layer begins a process called as suberization in which suberin, a waxy chemical found in cork, builds up in the cells. This provides an area of tissue thats impervious to the outside elements.The suberized protective layer prevents leaf fall from leaving open wounds on the twigs. While the protective layer is becoming filled with corky tissue, the abscission layer also transforms.

In trees, the growth rings represent

Solution: Trees have two types of growth: primary growth and secondary growth. ... Cambium lies between the old wood and the bark of the tree. The vascular cambium is a thin layer cells that produces conducting cells – xylem and phloem.

Annual rings are the bands of


The fibres usually occur in clusters or as bands alternating with bands of sieve tubes and parenchyma cells. As the vascular cambium continues to produce more secondary xylem to the inside, the older (most exterior) portions of the secondary phloem are crushed, die, and are sloughed off as part of the bark.


Annual rings and growth rings are formed due to the fluctuations in the activity of


Due to differential seasonal activity of cambium,alternate light & dense wood is cut off leading to formation of annual rings.


Growth rings are formed due to the activity of

Solution: As we know that Intrafascicular/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, 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.

Complementary cells are formed by the activity of

Solution: Complementary cells are a mass of cells in plants , formed from the cork cambium .... Cork cambium is also known as PHELLOGEN ... complementary cells are formed at the position of Lenticels ... it is a group of lossely arranged cell that .... aid in gaseous exchange throughout cork ... Hence , option C is correct ...

Knots are formed in the wood due to -

Solution: 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. Some knots are formed by fungal infections, however, and can spread to other trees on your property as well.

When a tree grows older which of the following increase rapidly -

Correct Answer: C
Solution :
As tree grows older, xylem vessels of heart wood are no longer involved in water transport and gets impregnated with organic compound like tannin, resin and oil due to which it becomes dark and increase in thickness. Cortex is commonly of thin walled parenchymatous cells that lies between endodermis and hypodermis or epidermis. Phloem is a tissue in the vascular system of plants that moves dissolved sugars and other products of photosynthesis from the leaves to other regions of the plant. Phloem tissue consists of cell called sieve tubes and companion cells. Sapwood is the layer of secondary xylem that are still functional in older woody plants, visible as the outer lighter areas in the cross section of a tree trunk.

Sap wood differ from heart wood in being -


Sapwood is the living, outermost portion of a woody stem or branch, while the heartwood is the dead, inner wood, which often comprises the majority of a stems cross-section. Sapwood is usually lighter in color than heartwood. Heartwood is also called as 'duramen', dead, central wood of trees. It's cells usually, contain tannins or other substances that make it dark in color and sometimes aromatic. Heartwood is mechanically strong, resistant to decay and less easily penetrated by wood preservative chemicals than other types of wood. One or more layers of living and functional sapwood cells are periodically converted to heartwood. Thus, option C is correct.


Sap wood is

Sapwood is the living, outermost portion of a woody stem or branch, while heartwood is the dead, inner wood, which often comprises the majority of a stem's cross-section. You can usually distinguish sapwood from heartwood by its lighter color.

In which of the following there is no differntiation heart wood and sap wood


Heart wood and sap wood are the result of sufficient activity of vascular cambium. Heart wood is the central region of old trees, that is formed earlier during secondary growth, with tannins, resin and other substances imparting it the black color. It serves to provide mechanical support. Sap wood in outer region of recently formed wood which is lighter in color. Vascular cambium is a lateral cambium which is produced by primary permanent tissues and divides to produce secondary tissues during secondary growth which in turn increase the girth of the plants. Monocots do not produce lateral cambium and hence lack secondary growth which means that heart wood and sap wood are not produced. Among the given options, palm is a monocot which does not produce secondary wood and rest three plants are dicots that exhibit secondary growth to produce secondary tissues. 


In older woody tissue, the gaseous exchange takes place through

Solution: Respiration In Stems. In the plants having herbaceous stem exchange of gases takes place through stomata and the carbon dioxide produced during the process gets diffused into the air via stomata only. While in the plants having hard and woody stems the exchange of gases takes place through lenticels.

Lenticels do not occur on

Solution: A leaf is an organ of a vascular plant and is the principal lateral appendage of the stem. The leaves and stem together form the shoot. Leaves are collectively referred to as foliage, as in "autumn foliage".In woody plants, lenticels commonly appear as rough, cork-like structures on young branches. Underneath them, porous tissue creates a number of large intercellular spaces between cells. ... Discoloration of lenticels may also occur, such as in mangoes, that may be due to the amount of lignin in cell walls.

Lenticels and its complementary cells are developed through the activity of


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. 


External Protective tissues are

Solution: Answer: As the plants grow older, the outer protective tissue (i.e., epidermis) undergoes certain changes. A strip of secondary moisten, called halogen or cork cambium replaces the epidermis of the stem.It's cells prevent desiccation (loss of water from plant body), infection and mechanical injury.

Successive ring of vascular cambium is found in :-
(a) Cycas stem
(b) Gnetum ula stem
(c) Pinus stem
(d) Sunflower stem


Cycas and Gnetum are gymnosperms and show wide range of distribution from tropical rain forest to temperate and desert i.e. they are found in the places showing clear transition of season from winter-autumn-summer-spring.Temperate plants exhibit cambial activity in spring and autumn seasons i.e. twice a year. Cambium is more active in spring and forms more number of vessels with wider cavities. The increased number of leaves during spring puts a demand for additional vessels to supply sap to new leaves. Autumn season is marked by lesser number of leaves and hence, decreased sap transport which makes cambium less active. It produces narrow pitted vessels and tracheids. Thus, spring and autumn woods form distinct concentric rings in temperate regions. Due to absence of visible difference between early and late wood of tropical angiosperms (sunflower), caused by more or less uniform climate, pores are uniformly distributed throughout the ring Alpine and cold winter regions are covered with ice throughout the year and thus no differential activity of cambium which is prerequisite for annual growth ring formation. Pinus is present in alpine, snow covered regions where winters last for  months in a year and there is no clear demarcation of different seasons. 
Therefore, the correct answer is option B.


If a stem is girdled


Girdling refers to a process in which the bark encircling the tree is removed completely. The phloem layer of tissue is present just beneath the bark, and it is responsible for the transportation of food prepared in the leaves of the plant through photosynthesis to the roots. Thus, phloem facilitates downward movement of food, and if the stem is girdled the roots of the plant will not able to capture food and die first.


Which would do maximum harm to a tree


The loss of half of branches does not harm the tree much, as half of the branches are present to carry out photosynthesis and transpiration. This condition we can see in real day to day life also that if the half of the branches are cut down then also tree can be alive. 
Shedding of all leaves is carried out by the plant itself but it does not harm the tree. Soon after shedding, the new leaves can be observed on the tree. 
The bark is the outermost layer of the stems of the woody plants. All the tissues outside the vascular cambium are called as bark. It protects the tree from wear and tear, bacterial infection and water loss. If all of the bark of the tree is removed then water loss will dry out the tree and tree will also become vulnerable to infections. 
So, the correct answer is 'Loss of all its bark'


Cambium cells divide in which plane


Cambium cells are the layer of delicate meristematic tissue found between the phloem and the xylem. Present in the stems and roots, the division of these cells gives rise to new phloem on the outside and new xylem on the inside thus bringing about the  secondary growth in plants and forming the annual rings. These cells divide tangentially in a plane parallel to the surface of the stem.


Vascular cambium cuts cells more activity -


The lateral flow of auxin determines the differential activity of vascular cambium. Phloem differentiation requires lower auxin concentrations as compared to those required by xylem differentiation. The initial increase in auxin concentration initiates the phloem differentiation which in turn induces xylem differentiation when the required auxin concentration is reached which is maintained towards the inner side. That’s why vascular cambium exhibit higher activity towards centre and differentiation of xylem is always associated with that of phloem.
Therefore, the correct answer is option A.

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