Please refer to the Anatomy of Flowering Plants Notes Class 11 Biology given below. These revision notes have been designed as per the latest NCERT, CBSE, and KVS books issued for the current academic year. Students will be able to understand the entire chapter in your class 11th Biology book. We have provided chapter-wise Notes for Class 11 Biology as per the latest examination pattern.
Revision Notes Chapter 8 Anatomy of Flowering Plants Class 11 Biology
Students of Class 11 Biology will be able to revise the entire chapter and also learn all important concepts based on the topic-wise notes given below. Our best teachers for Grade 11 have prepared these to help you get better marks in upcoming examinations. These revision notes cover all important topics given in this chapter.
1. Study of internal structure of plants is called Anatomy. (Plant Anatomy)
2. Different organs in a plant show differences in their internal structure due to different functions.
3. Within angiosperms, the monocots and dicots are also seen to be anatomically different.
4. Internal structures also show adaptations to diverse environments so environment influence the anatomy of organism.
5. A tissue is a group of cells having a common origin and usually performing a common function.
6. On the basis of division capacity, plant tissue is of two type.
o Meristematic tissue
o Permanent tissue.
7. Meristematic tissue:
o Cells of meristematic tissue have division capacity.
o Root tip and shoot tip are the example of apical meristem.
8. Axillary bud is the “left behind “part of the shoot tip. Such buds are present in the axils of leaves and are capable of forming a branch or a flower.
9. Intercalary meristem is the meristematic tissue present between permanent tissue and they are responsible for primary growth. They occur in grasses and regenerate parts removed by the grazing herbivores.
10. Both apical meristems and intercalary meristems are primary meristems because they appear early in life of a plant and contribute to the formation of the primary plant body.
11. Secondary / lateral meristem/ cylindrical meristems: Fascicular vascular cambium,interfascicular cambium and cork-cambium are examples of lateral meristems. These are responsible for producing the secondary tissues (increase in girth).
12. Permanent tissue:
o These are newly formed cells from meristematic tissue
o Structurally and functionally specialised.
o They don’t have division capacity.
o Permanent tissue is of two types à Simple tissue and Complex tissue.
o Permanent tissues having all cells similar in structure and function à simple tissues.
o Permanent tissues having many different types of cells à Complex tissues.
o Simple tissue is of three types:
§ Parenchyma.
§ Collenchyma
§ Sclerenchyma.
13. PARENCHYMA:
o Forms the major component within organ.
o Their walls are thin and made up of cellulose.
o The parenchyma performs various functions like photosynthesis, storage,secretion.
14. COLLENCHYMA:
o It consists of cells which are much thickened at the corners due to a deposition of cellulose, hemicellulose and pectin.
o Intercellular spaces are absent.
o They provide mechanical support to the growing parts of the plant such as young stem and petiole of a leaf.
o They make hypodermis in dicots.
o It is found either as a homogeneous layer or in patches.
15. SCLERENCHYMA:
o It consists of long, narrow cells with thick and lignified cell walls having a few or numerous pits.
o They are usually dead and without protoplasts.
o sclerenchyma tissue is two type fibres and sclereids.
o FIBRES are thick-walled, elongated and pointed cells, generally occurring in groups.
o SCLEREIDS are spherical, oval or cylindrical, highly thickened dead cells with very narrow cavities (lumen). These are commonly found in the fruit walls of nuts; pulp of fruits like guava, pear and sapota; seed coats of legumes and leaves of tea.
o Sclerenchyma provides mechanical support to organs.
16. COMPLEX TISSUE:
o Made of more than one type of cells and these works together as a unit.
o Xylem and phloem are complex tissue.
17. XYLEM:
o Conduct mineral and water in upward direction
o Also provide mechanical support to plant because of lignified wall.
o It is composed of four different kinds of elements, namely,
§ tracheids,
§ vessels,
§ xylem fibres and
§ xylem parenchyma.
o Gymnosperms lack vessels in their xylem.
o Tracheids are elongated or tube-like cells with thick and lignified walls and tapering ends. These are dead and are without protoplasm.
o Vessel is a long cylindrical tube-like structure made up of many cells called vessel members.
o Each cells of vessel are with lignified walls & a large central cavity and dead.
o Vessel members are interconnected through perforations in their common walls.
o The presence of vessels is a characteristic feature of angiosperms.
o Xylem fibres have highly thickened wall so there is no lumen.
o Xylem parenchyma cells are the only living cell in xylem and thin-walled, and their cell walls are made up of cellulose.
o The radial conduction of water takes place by the ray parenchymatous cells.
o Protoxylem (early formed xylem) & metaxylem (late formed xylem) are two type of primary xylem.
o Stem shows ENDARCH arrangement of xylem in which protoxylem is towards centre and metaxylem is towards periphery.
o The root shows EXARCH condition where protoxylem is towards periphery and meta xylem is located towards centre.
18. PHLOEM:
o Phloem transports food materials, usually from leaves to other parts of the plant.
o Phloem in angiosperms is composed of sieve tube elements, companion cells(parenchymatous), phloem parenchyma and phloem fibres.
o Gymnosperms have albuminous cells and sieve cells. But they lack sieve tubes and companion cells.
o Sieve tube elements are also long, tube-like structures, arranged longitudinally and are associated with the companion cells.
o Their end walls are perforated in a sieve-like manner to form the sieve plates.
o A mature sieve element possesses a peripheral cytoplasm and a large vacuole but lacks a nucleus.
o The functions of sieve tubes are controlled by the nucleus of companion cells.
o The sieve tube elements and companion cells are connected by pit fields present between their common longitudinal walls.
o The companion cells help in maintaining the pressure gradient in the sieve tubes.
o Phloem parenchyma is made up of elongated, tapering cylindrical cells, having cellulosic cell wall and has plasmodeta connection through pits.
o Phloem parenchyma is absent in most of the monocotyledons.
o Phloem fibres (bast fibres) are made up of sclerenchymatous cells.
o These are generally absent in the primary phloem but are found in the secondary phloem.
o Phloem fibres of jute, flax and hemp are used commercially.
o The first formed primary phloem consists of narrow sieve tubes and is referred to as protophloem and the later formed phloem has bigger sieve tubes and is referred to as metaphloem.
19. The Tissue System:
o THE EPIDERMAL TISSUE SYSTEM forms the outer-most covering of the whole plant body and comprises epidermal cells, stomata and the epidermal appendages – the trichomes and hairs.
o It is the outermost (usually single layer) layer of the primary plant body. It is made up of parenchyma cells.
o Epidermis of aerial parts of plant has waxy deposition called cuticle to prevent loss of water.
o Cuticle is absent in root.
o Stoma(plural: stomata) is the aperture, composed of two guard cells and present in epidermis for gaseous exchange and transpiration.
o In dicot guard cells are bean shaped whereas in monocots (grass) it is dumbbell shape.
o The outer walls of guard cells (away from the stomatal pore) are thin and the inner walls (towards the stomatal pore) are highly thickened.
o The guard cells possess chloroplasts and regulate the opening and closing of stomata.
o Subsidiary cells are specialized cells epidermis cells near the guard cell.
o The stomatal aperture, guard cells and the surrounding subsidiary cells are together called stomatal apparatus.
o The root hairs are unicellular elongations of the epidermal cells and help absorb water and minerals from the soil.
o The epidermal hairs on stem are called trichomes.
o Trichomes are generally multicellular whereas root hair is unicellular.
o The trichomes help in preventing water loss due to transpiration.
20. THE GROUND TISSUE SYSTEM
o All tissues except epidermis and vascular bundles constitute the ground tissue.
o It consists of simple tissues such as parenchyma, collenchyma and sclerenchyma.
o Parenchymatous cells are usually present in cortex, pericycle, pith and medullary rays, in the primary stems and roots.
o In leaves, the ground tissue consists of thin-walled chloroplast containing cells and is called MESOPHYLL.
21. THE VASCULAR TISSUE SYSTEM
o The vascular system consists of complex tissues, the phloem and the xylem and make vascular bundle.
o The vascular bundles form the conducting tissue and translocate water, minerals and food material.
o Open vascular bundle: In dicotyledonous stems, cambium is present between phloem and xylem.
o Cambium forms secondary xylem and secondary phloem during secondary growth i.e. increase in girth.
o CLOSED VASCULAR BUNDLE: cambium is absent between xylem and phloem in monocot stem.
o RADIAL VASCULAR BUNDLE: When xylem and phloem within a vascular bundle are arranged in an alternate manner on different radii. E.g. roots.
o CONJOINT TYPE: The xylem and phloem are situated at the same radius of vascular bundles’. e.g. leaves and stem.
o The conjoint vascular bundles usually have the phloem located only on the outer side of xylem.
22. STELE à All tissues on the inner side of the endodermis such as pericycle, vascular bundles and pith constitute the stele.
23. MONOCOTYLEDONOUS ROOT
o Monocot root differ from dicot root in:
§ there are usually more than six (polyarch) xylem bundles in the monocot root. (in dicot it is 2 -4 xylem bundle).
§ Pith is large and well developed.
§ Monocotyledonous roots do not undergo any secondary growth.
24. DICOTYLEDONOUS STEM
o In typical young dicotyledonous stem shows that the epidermis is the outermost protective layer of the stem having cuticle, trichomes and few stomata.
o Cortex is consist of three sub layers namely Hypodermis, Cortex and Endodermis.
o Hypodermis: The outer layer of cortex, consists of a few layers of collenchymatous cells just below the epidermis, which provide mechanical strength to the young stem.
o Cortical layers below hypodermis consist of rounded thin walled parenchymatous cells with conspicuous intercellular spaces.
o The innermost layer of the cortex is called the ENDODERMIS.
o The cells of the endodermis are rich in starch grains and the layer is also referred to as the STARCH SHEATH.
o PERICYCLE is made up of sclerenchyma and present above the phloem in semi-lunar patch and few celled thick.
o Medullary cells are radially placed parenchyma cells between vascular bundles.
o Each vascular bundle is conjoint, open, with endarch protoxylem and arranged in ring.
o Pith occupy central place of stem.
25. MONOCOTYLEDONOUS STEM
o The monocot stem has a sclerenchymatous hypodermis, a large number of scattered vascular bundles, each surrounded by a sclerenchymatous bundle sheath, and a large, conspicuous parenchymatous ground tissue.
o Vascular bundles are conjoint and closed.
o Peripheral vascular bundles are smaller than the centrally located ones.
o The phloem parenchyma is absent, and water-containing cavities are present within the vascular bundles.
26. DORSIVENTRAL (DICOTYLEDONOUS) LEAF
o There are mainly three types of tissue namely epidermis, mesophyll and vascular bundle.
o Epidermis present both side upper(adaxial) and lower side (abaxial side).
o Abaxial surface has more stomata than adaxial surface.
o Cuticle present both side.
o Mesophyll present between upper & lower epidermis.
o Mesophyll cells are basically parenchyma cell having chloroplast.
o They are differentiated in elongated PALISADE TISSUE and rounded
SPONGY PARENCHYMA.
o Palisade tissue are towards adaxial side and spongy parenchyma is located towards lower epidermis.
o Spongy parenchyma has large air cavities and intercellular space.
o Vascular bundles are located at midrib and veins.
o The size of vascular bundle is depending upon size of vein.
o The vascular bundles are surrounded by a layer of bundle sheath cells.
o Dicot leaf has reticulated venation.
27. ISOBILATERAL (MONOCOTYLEDONOUS) LEAF
o Stomata present on both side of leaf.
o Mesophyll cells are not differentiated into palisade and spongy parenchyma.
o Bulliform cells are modified epidermal cells on veins regulate the leaf surface exposure and curling in monocot leaf.
o Bulliform cells are larger than epidermal cells. When they are turgid the leaf surface is exposed, if they are flaccid the leaf curling occur.
o Because of parallel venation, there is almost vascular bundles are similar in size except midrib.
o Mid rib vascular bundles are bigger in size.
28. SECONDARY GROWTH
o Secondary growth is increase in girth/diameter.
o The tissues involved in secondary growth are the two lateral meristems: VASCULAR CAMBIUM AND CORK CAMBIUM.
o Vascular cambium is meristematic in nature and present between xylem and phloem is called intrafasicular cambium.
o Interfasicular cambium is present between two intrafasicular cambium, it is secondary in origin .
o Medullary cells present between vascular bundle become meristematic and change into interfasicular cambium.
o Intrafasicular and interfascicular cambium make a complete ring which produce secondary phloem toward periphery and secondary xylem towards central side.
o The cambium is generally more active on the inner side than on the outer.
So, the amount of secondary xylem produced is more than secondary phloem and forms a compact mass.
o The primary and secondary phloem is crushed due to continuous formation of secondary xylem.
o The primary xylem remains more or less intact, in or around the centre.
o Secondary medullary rays are produced by cambium ring.
o They pass through secondary xylem and secondary phloem and responsible for radial conduction of mineral water and food.
29. SECONDARY GROWTH IN ROOTS
o In the dicot root, the vascular cambium is completely secondary in origin and originate from pericycle.
o Pericycle located just below the primary phloem and above the protoxylem forming a complete and continuous wavy ring, which later becomes circular.
o After cambium ring formation, the pattern of secondary growth is same in dicot root and dicot stem.
30. SPRING WOOD AND AUTUMN WOOD
o The activity of cambium is under the control of many physiological and environmental factors.
o In the spring season, cambium is very active and produces a large number of xylary elements having vessels with wider cavities. (due to favourable season).
o This wood is lighter in colour and has a lower density is called spring wood or early wood.
o In winter, the cambium is less active and forms fewer xylary elements that have narrow vessels (less availability of water) and this wood is called autumn wood or late wood. the autumn wood is darker and has a higher density.
o The two kinds of woods (spring +autumn) that appear as alternate concentric rings, constitute an annual ring. Annual rings seen in a cut stem give an estimate of the age of the tree.
31. HEART WOOD:
o In old trees, the greater part of (centrally located) secondary xylem is dark brown due to deposition of organic compounds like tannins, resins, oils,
gums, aromatic substances and essential oils.
o These substances make it hard, durable and resistant to the attacks of microorganisms and insects. This region comprises dead elements with highly lignified walls and is called heartwood.
o The heartwood does not conduct water but it gives mechanical support to the stem.
32. SAP WOOD:
o The peripheral region of the secondary xylem, is lighter in colour and is known as the sapwood.
o It is involved in the conduction of water and minerals from root to leaf. (physiological active)
o Heart wood and sap wood both contain spring wood as well as autumn wood.
33. CORK CAMBIUM
o Cork cambium is lateral meristem and secondary in origin.
o It is originated in cortical zone.
o Cork cambium or phellogen is a couple of layers thick. It is made of narrow, thin-walled and nearly rectangular cells.
o Phellogen cuts off cells on both sides.
o The outer cells differentiate into cork or phellem while the inner cells differentiate into secondary cortex or phelloderm.
o The cork is impervious to water due to suberin deposition in the cell wall. It performs the function of epidermis i.e. protection as epidermis is destroyed by activity of cambium ring during secondary growth.
o The cells of secondary cortex are parenchymatous.
o Phellogen, phellem, and phelloderm are collectively known as PERIDERM.
o Due to activity of the cork cambium, pressure builds up on the remaining layers peripheral to phellogen and ultimately these layers die and slough off.
34. BARK is a non-technical term that refers to all tissues exterior to the vascular cambium.
o Bark includes a number of tissue types, viz., periderm and secondary phloem.
o Bark that is formed early in the season is called early or soft bark.
o Towards the end of the season, late or hard bark is formed.
35. LENTICELS:
o At certain regions, the phellogen cuts off closely arranged parenchymatous cells on the outer side instead of cork cells.
o These parenchymatous cells soon rupture the epidermis, forming a lens shaped opening called lenticels.
o Lenticels permit the exchange of gases between the outer atmosphere and the internal tissue of the stem. These occur in most woody trees
