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For a critical study of secondary growth in plants. Which one of the following pairs is suitable?
Teak and pine is most suitable for the study of critical secondary growth because in secondary growth, secondary tissues are formed from lateral meristem which is well developed in these two cases and secondary growth occurs in gymnosperms and dicots.
A common structural feature of vessel elements and sieve tube elements are
In plant conducting tissue xylem has an important integral cell as xylem vessel which is without nucleus. The phloem on other hand has a row of sieve tubes which are also without nucleus at maturity.
In a woody dicotyledonous tree, which of the following parts will mainly consist of primary tissues?
Primary Meristems : They are those meristematic tissues which are dervied directly from the meristems of the embryo and retain their meristematic activity. They are present at root, shoot tip and leaf primordia.
Ectophloic siphonostele is found in
The central pith is surrounded by xylem, phloem, pericycle and endodermis . The phloem occurs only outside the xylem e.g Equisetum, Osmunda.
The most abundant element present in the plants is
Manganese and Iron are micronutrients required in trace amounts. Concentration of nitrogen in dry matter-15000 mg./ gm. Concentration of carbon in dry matter is 45,000 mg / gm.
In a longitudinal section of a root, starting from the tip upward, the four zones occur in the following order:
Root shows the following regions Root cap or calyptra - caplike protective covering over tip of the root Meristematic region is the subapical position Zone of elongation - receives news cells from the growing point Root hair zone - is the zone of differentiation Zone of mature cells - having thick walled impermeable cells.
Chlorenchyma is known to develop in the
Chlorenchyma cells are those parenchymatous cell which contain chloroplast in them. They are capable of photosynthesis. A spore capsule of moss can perform photosynthesis, therefore chlorenchyma are present in them.
The apical meristem of the root is present
The apical meristem of the root is present at all the root tips. Apical meristem is subterminal in position of the growing root tips and responsible for terminal growth of the root of plants.
The cells of the quiescent centre are characterised by
The quiescent centre or QC is a part of the root-promeristems that contains the initials of epidermis, cortex and stele.
The cells here divide less frequently as they are inactive and are present at the pole of cortex and stele.
The cells with QC have small dictyosomes, nuclei and nucleoli with little cytoplasm.
These cells also have little endoplasmic reticulum, mitochondria and contain low concentrations of RNA, DNA and protein than the other cells of the root apex.
So, the correct answer is 'Light cytoplasm and small nuclei'.
Which of the following statements is true?
Vessels are elongated, multicellular water conducting channels with wide lumen formed by end to end fusion of a large number of vessel elements. Tracheids are elongated dead cells with tapering ends having lignified walls and large or wide lumen. Their main function is conduction of water and minerals from root to leaf.
Axillary bud and terminal bud are derived from the activity of
Apical meristem is located at the apex of stem, root and their branches and forms axillary bud & terminal bud. Intercalary meristems take part in linear growth. Lateral meristem occur parallel to the circumference of the organs. They increase girth of the plant.
Four radial vascular bundles are found in
When xylem and phloem strands are present at different radii the vascular bundles are radial and 4 radial vascular bundles (tetrach condition) are present in dicot root. This is called tetrach conditions.
Vessels are found in
Generally gymnosperms do not have vessels but a few gymnosperms having vessels are Ephedra, Smilax etc. Most of angiosperms have vessels except of few e.g., Trochodendron.
Main function of lenticel is
Lenticel is a pore found in the epidermis of leaves,stem and other organs that are used to control gas exchange. It provides a way for the exchange of gases like carbon dioxide, oxygen and water vapour with the atmosphere through the bark, which is otherwise impermeable to gases.
Thus, the correct answer is option C.
Loading of pholem is related to
Phloem is involved in transport of organic food. According to mass flow hypothesis organic substances flow in solution form in sieve elements due to development of an osmotically generated pressure gradient.
What happens during vascularization in plants?
Vascularization of plant means the development of vascular bundle in the plant, which develops from the cambium.
Transition of radial vascular bundle in root to conjoint vascular bundle in stem occurs in which zone?
Transition of radial vascular bundle in root to conjoint vascular bundle in stem occurs in transition zone which is generally hypocotyl. Hypocotyl is the part of embryonal axis below the level of cotyledons.
Which of the following meristems is responsible for extrastelar secondary growth in dicotyledonous stem?
Intrafascicular cambium occurs inside the vascular bundles in between xylem and phloem. Interfascicular cambium develops in the form of strips at the level of intrafascicular cambium of vascular bundles. Intercalary meristem lie in between areas of permanent tissues.
A leaf primordium grows into the adult leaf lamina by means of
A leaf primordium grows into the adult leaf lamina by means of first by apical meristem and later by marginal meristems.
At maturity which of the following is enucleate?
At maturity all physiological functions of sieve tube takes place in companion cell, since the sieve tube elements lose their nucleus at maturity.
What is not true about sclereids?
Sclereids are small bundles of sclerenchyma tissue in plants that form durable layers, such as the cores of apples and the gritty texture of pears. Sclereids are variable in shape. The cells can be isodiametric, prosenchymatic, forked or fantastically branched. The cell walls fill nearly all the cell’s volume. The shell of many seeds like those of nuts as well as the stones of drupes like cherries or plums are made up from sclereid.
As the secondary growth takes place (proceeds) in a tree, thickness of
Heartwood is the central wood of mature dicot stem and is the nonfunctional part of secondary xylem.
The meristematic tissue which forms the primary xylem and phloem is konown as procambium . The term procambium is used to indicate the meristematic tissue that give rise to the morphological vascular units.
A narrow layer of thin walled cells found between phloem/bark and wood of a dicot is
Vascular cambium is produced by two types of meristems, fascicular and interfascicular cambium.
Periderm is produced by
Secondary ground tissue or periderm is formed from phellogen or cork cambium. The phellogen forms phellem on the outer face and phelloderm on the inner. The three layers i.e., phellem, phellogen and phelloderm jointly constitute the periderm.