Spring wood (early wood) differs with autumn wood (late wood) in -
The growth ring closer to the centre of the tree, and formed early in the growing season (when the growth is rapid) is usually composed of wider elements. It is usually light in color as compared to the outer ring and is called springwood (earlywood). The outer ring is called winterwood (latewood).
Most conspicuous annual rings form 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 temperate regions. In deserts annual rings are less distinct. Annual rings are bands of secondary xylem and xylem rays
So, the correct answer is 'Temperate deciduous plants'
Formation of vascular rays occurs in which order
The vascular cambium that gives rise to secondary xylem consists of fusiform and ray initials. The ray initials of the vascular bundle divide tangentially and produce cells on both sides, which differentiate as parenchymatous vascular rays.
These rays traverse from pith to cortex through secondary xylem and phloem. Growth pattern that moves towards the centre is called as 'centripetal', while those moving outwards away from centre is called as 'centrifugal'. Since the tangential, division is followed, the rays are produced in both directions.
Whereas acropetal order refers to development in succession from base to apex; it is normally used to refer the developmental pattern in leaves and flower.
Which of the following provide maximum mechanical strength to a tree trunk.
Youngest layer of secondary xylem is located
Diffuse porous woods are characteristic of plants growing in
Bottle cork is obtained from
Inner bark composed of
Living tissue in lenticel is called
A lenticel is a porous tissue consisting of cells with large intercellular spaces in the periderm of the secondarily thickened organs and the bark of woody stems and roots of dicotyledonous flowering plants. It functions as a pore, providing a pathway for the direct exchange of gases between the internal tissues and atmosphere through the bark, which is otherwise impermeable to gases.
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. Sometimes, complementary cells produced by phellogen towards outside instead of producing cork cells. Complementary cells are living cells in lenticles. Conjunctive tissue, connective tissue and phelloderm are not the living tissue in lenticel
Stem of date palm increases in girth due to activity of
Most monocots either have no secondary growth or else anomalous secondary growth of some type. For example, palm trees increase their trunk diameter due to division and enlargement of parenchyma cells, which is termed as 'diffuse secondary growth'. In some other monocot stems with anomalous secondary growth, a cambium forms but it produces vascular bundles and parenchyma internally and just parenchyma externally. Some monocot stems increase in diameter due to the activity of a primary thickening meristem, which is derived from the apical meristem. Stem of date palm increases in girth due to activity of apical meristem and not because of intercalary meristem and lateral meristem (involves in normal secondary growth of dicots).
Normal secondary growth takes place in
Select true statements :-
(a) Lenticels are absent in woody climbers
(b) Lenticels occur in most woody trees
(c) The spring wood is lighter in colour and has a lower density
(d) The sap wood also called as duramen
A lenticel is a porous tissue consisting of cells with large intercellular spaces in the periderm of the secondarily thickened organs and the bark of woody stems and roots of dicotyledonous flowering plants. It functions as a pore, providing a pathway for the direct exchange of gases between the internal tissues and atmosphere through the bark, which is otherwise impermeable to gases. Lenticels are absent in woody climbers.
Heart wood is also called as 'duramen'. The spring wood is lighter in colour and has a lower density.
Formation of secondary xylem and phloem respectively
A wood with scattered parenchyma is called
In dicot root which tissue becomes dead due to activity of phellogen
Pericycle is the outer most covering of stele, lying just beneath the endodermis. During secondary growth, the cells of pericycle present against protoxylem divide and form multiple layers of cells which are joined by cambial cells derived from conjunctive tissues and together they make a complete cambium ring. Cambial activity produces secondary tissues that push and rupture epidermal cell and outer cortex; a new protective layer, periderm is formed. Periderm divides to form cork cambium or phellogen. The cork cambium exhibit meristematic activity and produces cork or phellem towards the periphery and phelloderm on inside, i.e., extrastellar growth. These secondary tissues cause pressure and rupture the cells layers present outside the pericycle (endodermis and cortex)
A dicot root has tissues layers in following order: epidermis, cortex, endodermis, pericycle and vascular tissues, cork cambium activity rupture the cells layers present outside the pericycle. Hypodermis is the thickest layer of epidermis but is present in leaves not in roots
So, the correct answer is 'Tissue outside pericycle'
In dicot root, vascular cambium originates from
Dicot roots have little or no pith and thus pith rays are not the source of interfascicular cambium. The parenchyma cells present between xylem and phloem elements in the vascular bundles constitute conjunctive tissue. The parenchymatous cells present beneath phloem take on meristematic activity and form cambial strands. Similarly, the cells of pericycle present against protoxylem divide and form multiple layers of cells, which are joined by cambial cells derived from conjunctive tissues and together they make a complete cambium ring. Thus, the correct answer is option D.
In a hollow stem, what is most affected
Hollow stem is characterized by the disintegration of pith leaving the central space empty which is otherwise occupied by pith. The disintegration of pith is caused by rapid elongation and radial expansion of growing stem. Translocation of organic nutrient and water is the function of phloem and xylem respectively and hence, the disintegration of pith does not affect these functions. Pith serves to store and transport the nutrient while the hollow stem contains water, storage of food is most affected in hollow stem.
Thus, the correct answer is option C.
Formation of which tissue is example of dedifferentiation
In which stem, lateral meristem is absent
Abnormal secondary growth occurs in
In dicot stem cork cambium first derived from
What happens to primary phloem in stem after sec growth
Which tissue remains more active during autumn
The highest activity of cork cambium is in winter (Autumn) season. Ring of cork cambium remains living only for one year. Each year, a new cambium is formed below the previous cambium. This new cambium is derived from the secondary cortex or phelloderm.
Water conduction in stem of tree takes place by
Sapwood is the younger, outermost wood in the growing tree. It is living wood and its principal functions are to conduct water from the roots to the leaves and to store up and give back according to the season the reserves prepared in the leaves. 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. The more leaves a tree bears and the more vigorous its growth, the larger the volume of sapwood required.
What is "Rhytidome":
The outer bark on trees is also called as the rhytidome. It lies external to the last formed periderm. It covers the trunks of trees. It is composed mostly of dead cells and is produced by the formation of multiple layers of suberized periderm, cortical and phloem tissue. It is generally thickest and most distinctive at the trunk or bole the area from the ground to where the main branching starts of the tree. So, rhytidome is the dead tissue separated by periderm on the outside and not dead tissue separated by periderm on the inner side, secondary cortex and bark.
In a woody dicotyledonous tree, which of the following parts will mainly consist of primary tissues?
Study of wood is called
How many types of cells are present in vascular cambium
The vascular cambium is located between the xylem and the phloem in the stem and root of a vascular plant and is the source of both the secondary xylem growth inwards, towards the pith and the secondary phloem growth outwards. It is a cylinder of unspecialized meristem cells that divide to give new cells, which then specialize to form secondary vascular tissues. The vascular cambium usually consists of two types of cells - fusiform initials and ray initials. The fusiform initial cells are tall cells and axially oriented. The ray initials are small and round. Sometimes, they are angular in shape.
Annual ring involves
Bark includes all the tissues
Bark is the outermost layers of stems and roots of woody plants. Plants with bark include trees, woody vines and shrubs. Bark refers to all the tissues outside of the vascular cambium and is a non-technical term. It overlays the wood and consists of the inner bark and the outer bark. The inner bark, which in older stems is living tissue, includes the innermost area of the periderm.
The outer bark in older stems includes the dead tissue on the surface of the stems, along with parts of the innermost periderm and all the tissues on the outer side of the periderm. The outer bark on trees which lies external to the last formed periderm is also called as the rhytidome. So, bark includes the tissue lying outside the vascular cambium and not of formed by vascular cambium, formed by phellogen and phellem and phelloderm.
Thus, the correct answer is option A.