Anatomy of Flowering Plants Class 11th PDF

# Anatomy of Flowering Plants ## Tissues ### Meristematic Tissues * Meristematic tissue * Growth in plants is largely restricted to specialized regions of active cell division called meristems. * Permanent tissue. #### Meristematic Tissue * **Apical meristem**: Occurs at root tips and shoot ti...

# Anatomy of Flowering Plants ## Tissues ### Meristematic Tissues * Meristematic tissue * Growth in plants is largely restricted to specialized regions of active cell division called meristems. * Permanent tissue. #### Meristematic Tissue * **Apical meristem**: Occurs at root tips and shoot tips. * **Root apical meristem**: Occupies the tip of a root * **Shoot apical meristem**: Occupies distant most region of the stem * **Intercalary meristem**: The meristem which occurs between mature tissues. They occur in grasses. * **Lateral meristem**: Meristem that occurs in body of plant * Contribute to the formation of secondary or lateral meristem: Cylindrical meristems * **Eg:** Fasicular vascular cambium, cork cambium, interfasicular cambium. * Responsible for producing the complex tissues. ### Permanent Tissues * **Simple tissue**: only one type of cells similar in structure & function * **Complex tissue**: 4 types of elements #### Simple tissues | Tissue | Characteristics | |---|---| | Parenchyma | Spherical, oval, round, polygonal or polygonal, elongated, thin walls, closely packed, small intercellular spaces, photosynthesis, storage, secretion | | Collenchyma | Oval, spherical, or polygonal, elongated, thickened corners, homogeneous layers, & without intercellular spaces, have chloroplasts, & mechanical support | | Sclerenchyma | Provides mechanical support, numerous parts, thick & lignified, usually dead, thickened cell walls, & without protoplast, types: Sclereids, fibers | ###### Parenchyma * Spherical, oval, round, polygonal or polygonal, elongated. * Thin walls, * Closely packed. * Small intercellular spaces. * Photosynthesis, storage, secretion. ###### Collenchyma * Oval, spherical, or polygonal, elongated. * Thickened corners. * Homogeneous layers, & without intercellular spaces. * Have chloroplasts, & mechanical support. ###### Sclerenchyma * Provides mechanical support. * Numerous parts. * Thick & lignified, usually dead. * Thickened cell walls, & without protoplast. * Types: * Sclereids - thick-walled spherical or elongated oval cells. * Fibers - highly thickened, dead cells with very narrow cavities. #### Complex Tissues | Tissue | Characteristics | |---|---| | Xylem | Conducting tissue for water & minerals from roots to stem & leaves, Mechanical strength | | Phloem | Conducting tissue for water & minerals, from leaves to other parts of plant | ###### Xylem * Conducting tissue for water & minerals (from roots to stem & leaves). * Mechanical strength. * It has 4 kinds of elements: * **Tracheids**: Elongated tube-like cells, thick & lignified walls, tapering ends, dead without protoplasm. * **Vessels**: Long vascular tube-like cells, lignified walls, vessel cells devoid of protoplasm. Vessels are absent in gymnosperms. * **Xylem fibers**: Highly thickened walls, obliterated central lumens, septate or aseptate. * **Xylem parenchyma**: Living cells, thin-walled, cell walls of cellulose, store food as starch. * *Note: Radial conduction of water takes place by the ray parenchymatous cells.* * **Protoxylem**: 1st formed xylem elements. * **Metaxylem**: Later formed xylem elements. ###### Phloem * Transports food materials from leaves to other parts of the plant. * 4 Types of elements: * **Sieve tube elements**: Long, tube-like structures, mature-peripheral cytoplasm, large vacuole, but lacks nucleus. * **Companion cells**: Closely associated with sieve tube elements, specialized parenchymatous cells. * **Pholem parenchyma**: Elongated, tapering cylindrical cells, dense cytoplasm & nucleus, cell-wall & cellulose, stores food - resins, latex & mucilage. * *Note: Pholem parenchyma is absent in most of the monocotyledons.* * **Pholem fibers**: Made up sclerenchyma cells, longated, unbranched & have pointed needle-like apices, cell wall - quite thick, mature - later formed waxy material & impermebale strips. ## Tissue Systems ### Epidermal Tissue System * **Epidermis**: Outer covering layer of plant body. * Elongated, single layer, compactly arranged cells. * Parenchymatous cells. * Small amount & large vacuole * Outerside - thick layer of cytoplasm * Innermost layer - cuticle prevents loss of water. * **Guard cells**: Outer wall - thin, inner wall - highly thickened, have chloroplasts, regulate opening & closing of stomatal aperture. * **Subsidary cells**: Specialized cells in their shape and size - occur on stem epidermis. * **Stomatal apparatus**: * **Guard cells**: * *In dicots*: * **Dumb-bell shape in grasses.** * **Mutual arrangement is present.** * **Anisocytic type of guard cells.* * **In monocots**: **Paracytic type of guard cells.* * **Subsidary cells**: Present only in dicotyledonous plants. ### Vascular Tissue System * Also called conducting tissue. * Consists of complex tissues. * Xylem & pholem vascular bundles. * **Xylem**: * **Open-type xylem**: Ability to form cambium. * **Closed-type xylem**: Cambium absent. * **Pholem**: * **Conjoint arrangement**: Xylem & phloem are arranged in alternate manner in different radii. * **Radial arrangement**: Xylem & phloem are jointly situated along the same radius. * **Conjoint vascular bundles usually have xylem on the outer side.* ### Ground Tissue * All tissues except epidermis & vascular bundles. * Consists of simple tissues - also called fundamental tissue. * **Leaves**: Have mesophyll cells. ## Secondary Growth * Most dicotyledonous plant exhibits an increase in girth; it's called secondary growth. * **Tissues Involved:** * **Vascular cambium**: Meristematic layer responsible for cutting off vascular tissues. * **Cork cambium**: Also called phellogen, it's a lateral meristem. * **Vascular cambium:** * Forms a continuous layering during spring wood & autumn wood. * Functions: It cuts off new cells on both sides. * Forms a ring and forms both xylem and phloem. * **Cork cambium:** * Develops from cortex region. * Forms a ring and forms cork (phellum) & secondary cortex (phelloderm). * **Phellogen + phellum + phelloderm = periderm (a new cortex)** ## Root * **Positively geotropic**: Grows towards the earth's center. * **Negatively phototropic**: Grows away from light. * **Root hairs are present.** * **Xylem is exarch**: Protoxylem is present near the periphery, while metaxylem is present towards the center. * **Conjunctive tissue is present.** * **Endodermis is clearly demarcated.** ## Stem * **Negatively geotropic**: Grows against the earth's center or upwards. * **Positively phototropic**: Grows towards light. * **Stem hairs are present - also called trichomes.** * **Xylem is endarch**: Metaxylem is present near the periphery, while protoxylem is present towards the center. * **Endodermis is present but not clearly demarcated.** ## Dicotyledonous root * **Outermost layer**: Endodermis. * **Cortex**: Parenchymatous cells with intercellular spaces. * **Innermost layer**: Pericycle - single layer, without intercellular spaces. * **Pith**: Large & well-developed. * **Xylem**: More than 6 (polyarch) xylem bundles are present in monocots. * **Pholem**: Absent. ## Monocotyledonous root * Similar to dicot roots. * Contains epidermis, cortex, endodermis, pericycle, vascular bundle & pith. * Have more than 6 polyarch xylem bundles. * Pith is large & well-developed. * **Secondary growth is absent.** ## Dicotyledonous stem * **Trichomes are present.** * **Cortex is well-developed & thicker.** * **Endodermis is present & demarcated.** * **Xylem is endarch.** * **Xylem bundles are highly reduced and represent atactostele.** ## Monocotyledonous stem * **Trichomes are absent** * **Cortex is highly reduced.** * **Endodermis is present in the form of fibrous sheath.** * **Xylem bundles are present in a scattered arrangement.** * **Pith is large & well-developed.** * **Bulliform cells are present.** * **Parallel venation.** ## Dicotyledonous leaf * **Trichomes are present.** * **Mesophyll is differentiated into palisade & spongy tissue.** * **Reticulate venation.** ## Monocotyledonous leaf * **Trichomes are absent.** * **Mesophyll is not differentiated into palisade & spongy tissues.** * **Parallel venation.** ### Note: * Stem hairs are present in dicot but absent in monocots. * **Secondary growth is absent in monocotyledonous plants.*