pinus leaves contain sunken stomata
4. Pinus are coniferous, evergreen resinous trees which are popularly known as pine. The antherdial cell again divides to form a small generative cell above and a large tube cell below. They are formed in clusters of 1-4 in the axils of scale leaves of long shoots. Besides these, white, black, Himalayan, and stone pines are cultivated as ornamental pine trees. Each megasporophyll consists of two types of scales, known as bract scales and ovuliferous scales. Below the secondary xylem are present a few groups of endarch primary xylem. Megasporophylls present in the middle of the strobilus are very large and they decrease in size towards the base and apex. 9. The plant body represents the sporophyte. The root is mycorrhizal because fungus grows on the surface of the root. Few resin canals are present in the mesophyll, adjoining the hypodermis. These are closed but cambium may also present in the sections passing through the base of the needle. What are the types of tissue systems found in the various organs of plants? Leaves are dimorphic: the long green needle shaped foliage leaves and small, brown, membranous scale leaves. Individual vascular bundles are separated by means of medullary rays. of young long shoot except following differences: 1. The male cones develop in clusters (Fig. 3. amzn_assoc_default_browse_node = "672123011"; amzn_assoc_placement = "adunit0"; A mature archegonium consists of a neck of eight cells, one ventral canal cell and a large egg. 3. (v) Sex organs are present in the form of cones…………. It is placed just underneath the epidermis. In the endosperm or female gametophyte are present 2 to 5 archegonia. 7. 1. Microsporophylls are arranged spirally on the central axis and forms male cone. In fact, only one of these embryos attains maturity and the others undergo degeneration. Each microsporangium produces a several microspores (pollen grains). Outer fleshy layer disappears. The anatomy of leaves shows xerophytic structure: thick cuticularised epidermis with sunken stomata and sclerenchymatous hypodermis. Crushed primary phloem is present outside the secondary phloem (Fig. (vi) Pericycle: It consists of albuminous cells and tracheidal cells. They also develop in the axil of scaly leaves on long shoots (Fig. It is hard woody and dry structure. 13. Endodermis and pericycle are indistinguishable. Often a branch roots are infested with mycorrhizal fungus and hence it is called the mycorrhizal root. The wall of each microspore is covered by inner intine and an outer exine. Turpentine oil is produced from the pine tree which is used as a solvent for varnishes, paints and in perfumery industry. Tracheids are composed of rectangular cells. 13. Between xylem and phloem, a narrow strip of cambium is present. 5. Radial Longitudinal Section (R.L.S.) amzn_assoc_region = "US"; 5. Cells of the mesophyll are polygonal and filled with chloroplasts. You might also read: Reproduction in Algae. 1. 12. amzn_assoc_tracking_id = "mywebsit03240-20"; 48C) details: 1. 10. Vascular bundles are radially arranged and diarch to tetrarch with exarch protoxylem. The phloem is composed of sieve tubes and phloem parenchyma without companion cells. 9. The lateral roots are well developed with insufficient root hairs. Many peg-like infoldings of cellulose also arise from the inner side of the wall of mesophyll cells. Each megasporophyll has short stalk with a large ovuliferous scale on the upper surface and a small bract scale on the lower surface. It is wavy in outline. 1. coniferales. Central part of the stem is filled with the parenchymatous pith. Transfusion tissue consists of tracheidial cells. One of the male gamete unites with the egg to form a diploid zygote. 4. Female gametophyte: The functional megaspore is the first cell of the female gametophyte. Uniseriate medullary rays run horizontally. 5. Pine oil from the pinewood is used in pharmaceutical industries, textile industries, leather industries, etc. 27) has two scaly leaves called prophylls, followed by 5-13 cataphylls arranged in 2/5 phyllotaxy, and 1-5 needles. 42). 3. If a section of distal end of dwarf shoot is cut, the needles get separated, each having the same structure. 2. 6. The stem is cylindrical and erect, and remains covered with bark. 4. It is green to reddish-green in colour. Reproductive Structures. 3. Many sunken stomata are present on the epidermis (Fig. 3. 4. In a bifoliar spur two needles are present while in a trifoliar spur there are present three foliage leaves or needles (Fig. the longitudinal section is cut along the tangent of the wood. 5. 11. 2. 7. 15. The leaf contains both the assimilating and conducting tissues, and either or both tissues could be affected by CO 2 (Assmann, 1999). amzn_assoc_ad_mode = "search"; 44). (v) Presence of resin canals in pith, cortex and wood. A single layered endodermis is present which is followed by a pericycle. The zygote is the first cell of the sporophyte which germinates almost immediately after its formation. 1. The number of the resin canals present in the cortex is not indefinite but generally six (Fig. The pine bears tap root system with insufficient hairs but it disappears soon. Scale leaves are thin and brownish in color which is developed only on long as well as dwarf shoots while the foliage leaves are large, needle-like and found only at the apex of the dwarf shoots. The nutritive tissue lies surrounding the embryo. 4. A dwarf shoot (Fig. Further development of microspores takes place when it reaches the ovule due to pollination. Plants. In between the hypodermis and endodermis is present the mesophyll tissue. Name the types of nitrogenous bases present in the RNA. It consists of a single layer of tubular close compact parenchymatous cells with a thick cuticle. Many scaly leaves are present on the long shoot. Sunken stomata are a feature of many plants in deserts and other dry environments. Branching is monopodial. 5. Secondary growth, similar to that of a dicotyledonous stem, is present in the old stem of Pinus. Cut thin sections of different parts of the plant (Young root, old root, young long shoot, old long shoot, T.L.S. Resin ducts are present in the mesophyll tissue and the cells of the mesophyll have ridges on the walls which project inside the cell cavities. 8. Leaf: The pine tree bears two types of leaves: The scale leaves: Both long and dwarf shoots bear scale-leaves and fall off as the branches attain maturity. Some pine trees are also sources of wood tars, resin, turpentine, and oils while some produce edible seeds such as pine nuts, piñons, or pinyons. (v) Vascular bundles: They are collateral, closed and two in number. Botany. Outermost layer is epidermis, which consists of thick-walled cells. It starts to produce in winter and become ready for pollination during the spring. Sunken stomata are a feature of many plants in deserts and other dry environments. It is bounded externally by cork, cork cambium, secondary phloem and crushed primary phloem. It strengthens the tissue of the leaf. or more in length. The male cones are simple, compact, oval structures and about 2-3 cm long. 6. Each dwarf shoot bear two scaly leaves which is also known as prophylls. Megasporophylls (Fig. It is covered by a very strong cuticle. Observe the external features and longitudinal section of a young female cone and also study 1st year, 2nd year and 3rd year female cones. It is also woody in nature like the 2nd year cone. Each ovuliferous scale bears two inverted megasporangia on its upper surface towards the base. Phloem is present alternate to the protoxylem. Some of the species with different types of spurs are as follows: (i) Pinus monophylla-unifoliar (having only one needle); (ii) P. sylvestris-bifoliar (having two needles); (iii) P. gerardiana-trifoliar (having three needles); (iv) P. quadrifolia-quadrifoliar (having four needles); (v) P. wallichiana-pentafoliar (having five needles). 3. They develop in clusters at the apex of the dwarf shoots and can form the spur. There is no neck canal cell. Thin-walled ray parenchyma is also present. Besides these, 2-3 archaegonia are formed with a neck of eight cells. Vascular bundles are conjoint, collateral, open and endarch, and resemble greatly with that of a dicot stem. Each ovuliferous scale bears two anatropous ovules or megasporangia.
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