Anatomy of Flowering Plants
Anatomy and functions
- Anatomy of Dicot Root: Young dicot root has an optical growing point made up of primary permanent tissues. Which is cylindrical in outline and passes following tissue.
- Epiblema / Piliferous layer / Rhizodermis: Consists of trichoblast that helps in absorption.
- Cortex: Thin walled parenchymatous cells [rounded eg: Cicer / Singular Eg: Sunflower]. Which contain inter cellular spaces.
- Endodermis: Biological checkpoint of cells because of presence of Casparian strips that is formed due to suberin/lignin deposition restricting apoplastic pathway.
- Pericycle is found next to endodermis (layered - Eg: Sunflower)(2/more layered - Eg: Mulberry)
- Pericycle → part of vascular combium
Pericycle → cork cambium
Pericycle → lateral roots.
- Vascular strand contains 2-6 alternately arranged bundles of xylem and Phloem.
- Vascular bundles for radial arrangement.
- Xylem bundles → Tetrarch (gram, sunflower)
Xylem bundles → Triarch (Pea)
Xylem bundles → diarch (Tomato)
- In between 2 adjacent Xylem bundles and Phloem there exist a conjunctive parenchyma tissue called vascular combium.
- Pith is generally absent and if it is present there is no intercellular space.
- Anatomy of mono cot root:
- In a mono cot root there is no distinction between young and old root as they show no secondary growth.
- Epiblema and cortex layer resembles dicot root
- Caspariant strip soon gets indistinguishable because of additional thickening of Endodermis.
- The cells opposite to protoxylem ends remain primary called Transfusion cells or passage cells.
- Pericycle is uniseriate in maize and multiseriate in similar and it does not give rise to cambium.
- Several radial, Xylem and Phloem bundles arrange in alternate way where it is 20-30 bundles in maize and 100 or more in palm and so the condition is called polyarch.
- Pith stores food with no Intercellular spaces.
- Anatomy of dicot stem: Various tissues of dicot stem arrange themselves is concentric rings where in outline if it is circular for sunflower and angular for cucurbita.
- Epidermis: In sunflower, unbranched multi cellular hair (or) trichomes are present and contain stomata.
- Cortex is of 3 main types:
(i) Hypodermis [Made of collenchyma tissue with inter cellular spaces]
(ii) General cortex [With intercellular spaces containing chloroplast and also passes running oil ducts called glandular cells]
(iii) Endodermis is a wary layer containing barrel shaped cells with no inter cellular space and casparian strips, but contain starch [starch sheath]
- Pericycle is heterogeneous containing both parenchyma and sclerenchyma (bundle cap) exception [Cucurbita - homogeneous]. Sclerenchymatous pericycle is also called hard bast.
- Arrangement of Xylem and Phloem is conjoint / collateral and open
- Arrangement of Xylem and endarch
- A narrow strip of primary meristematic cells called cambium is between Xylem and phloem which is also called Fascicular cambium, whose functions to give rise to secondary Xylem and phloem.
- Medullary rays or pith rays are the strips of parenchyma present between adjacent vascular bundles that connects pith to pericycle / cortex which allows radial conduction of food and water.
- Pith forms the centre of the stem. [cucurbita → central cavity]
- Anatomy of Monocot Root:
- Various tissues are not arranged in concentric fashion, where the stem is solid [maize] or fistular [grass]
- Epidermis - Outer walls have the deposition of silica and cutin and the dumb bell shaped stoma is also present for gaseous exchange.
- Hypodermis is made of sclerenchymatous fibers that acts as heat screen.
- Ground tissue is not distinguished into cortex, endodermis etc., where as the whole is made of parenchyma.
- Large number of vascular bundles are scattered in the ground tissue and it is termed as Atactostele.
- Vascular bundles → conjoint / closed.
- Bundle sheath cells surrounding Xylem and Phloem is absent in asparagus.
- Anatomy of leaf:
⇒ Leaf is of 3 different types → (i) Dorsiventral, (ii) Isobilateral, (iii) Unifacial
- Dorsiventral mesophytic leaf:
- The upper epidermis / adamial epidermis has no chlorophyll but cuticle and hairs may be present.
- The lower epidermis / abquial type bear large number of pores called Hypostomata
- Mesophyll is arranged into palisade and spongy parenchyma.
- Palisade : Compactness ∝ light intensity
Marrow inter cellular space.(ICS)
Chloroplast is the main seat of photosynthesis
- Spongy: Many shapes where chloroplast is less and the cells are loosely arranged with large I.C.S.
- The vascular bundles are conjoint and collateral where X and P lies on the same radius.
- Xylem contain all its 4 components but fibers are rare for phloem.
- In the midrib, mesophyll is absent.
- Isobilateral leaf:
- Epidermis is single layered in both sides of leaf, where it is compactly arranged with cuticle.
- At some places, bulliform / motor cells for the rolling / unrolling leaves are present.
- Stomatal presence: Amphistomatic condition
- The leaf contains no palisade and the whole layer resembles spongy.
- Mesophyll is chlorine chymatous.
- Large number of closely placed small and large vascular bundles are parallel to one another with bundle sheath cells being chlorenchymatous.
- Xylem exhibits endarch condition.
- Other leaf types:
- Multilayered epidermis [Eg: Ficus, Begonia, Nerium]
- Xerophytic leaves [spongy parenchyma is reduced] / sunken stomata.
- Spongy sandwiched between palisade : Nerium
- Epistomatic activity in Nymphal.
View this video for the topic from 0:59 to 51:09
Disclaimer: Compete.etutor.co may from time to time provide links to third party Internet sites under their respective fair use policy and it may from time to time provide materials from such third parties on this website. These third party sites and any third party materials are provided for viewers convenience and for non-commercial educational purpose only. Compete does not operate or control in any respect any information, products or services available on these third party sites. Compete.etutor.co makes no representations whatsoever concerning the content of these sites and the fact that compete.etutor.co has provided a link to such sites is NOT an endorsement, authorization, sponsorship, or affiliation by compete.etutor.co with respect to such sites, its services, the products displayed, its owners, or its providers.