Introduction to Seeds and Linseed PDF

The Seed  The seed Definition: It is a fertilized ovule which is matured and enlarged. Insure the continuation and distribution of the plant. Angiosperm : Seeds are surrounded by flower or fruit (ovary wall is present) Gymnosperm: Seeds are naked (ovary wall is absent)...

The Seed  The seed Definition: It is a fertilized ovule which is matured and enlarged. Insure the continuation and distribution of the plant. Angiosperm : Seeds are surrounded by flower or fruit (ovary wall is present) Gymnosperm: Seeds are naked (ovary wall is absent)  The Ovule ❑ Ovules are arranged on placentae in the ovaries They attached to the placentae by small stalk called funicle Mature typical ovule consists of: Mass of parenchymatous tissues called nucellus , enveloped with one or two integuments (coats) except in the micropyle region. Micropyle: minute pore through which pollination occur Chalaza: basal swollen part of nucellus, from which arise the integuments Types of ovules 1- Atropous "orthotropous" Ovule is straight having funicle, chalaza and micropyle on one straight line showing no raphe 2- Anatropous (e.g. Linseed) Ovule is inverted (bent upon funicle and fused with it), micropyle near placenta, raphe run from one end to another 3- Hemianatropous The ovule is rotated on its stalk through an angle of 90ο (partly bent) Micropyle, chalaza are on line at right angel to funicle Short raphe present. N.B.: in all 3 kinds the nucellus is straight 4- Campylotropous Ovule bent upon itself instead upon funicle (curved nucellus) Micropyle, chalaza and funicle all are close to one another. A typical seed consists of: 1- Embryo: develop from fertilized ovum 2- Endosperm: surrounding the embryo and develop from 1ry endosperm nucleus 3- Perisperm: formed from nucellus 4- Testa: formed of one or two seed coats originate from the integuments of the ovule  Seed structure 1- Testa 2- Kernel Marks On Testa: 1- Hilum Scar left at the point of attachment of seed to placenta 2- Micropyle 3- Raphe Fusion of funicle with the integuments appear as ridge running from hilum to some distance of the seed  Linseed ‫الكتان‬ ❖ Origin: dried ripe seeds of Linum usi tati si mum ❖ Fam: Linaceae  Morphology Condition: Dry Shape: Oval with broad rounded end and narrow tapering one, at which a small depression containing both hilum and micropyle. Color: Dark brown. Taste: Mucilagenous oily taste.  Morphology Testa: Surface: Shiny glossy and finely pitted Hilum and micropyle: Present in a small depression at the narrow tapering end. Raphe: Distinct yellow along the seed (Anatropous). Texture and thickness: Smooth Kind: Albuminous Perisperm: Absent. Endosperm: Present. Embryo: Straight. T.S & L.S parallel and perpendicular Pigment layer, Endosperm Embryo Description Testa Epidermis: Polygonal radially elongated cells filled with striated mucilage. Hypodermis: One or two layer of collenchyma cells. Sclerides: One layer of sclerides. Hyaline layer: Collapsed parenchyma. Pigment layer: One layer of tabular cells containing dark brown pigment. Endosperm Polyhedral parenchyma containing fixed oil and aleurone grain. Embryo Elongated parenchymatous cells containing fixed oil and aleurone grain.  Powder and Isolated elements o Fragments of pigment layer o Fragments of Endosperm containing aleurone grains o Fragments of cross layer (Mat-like structure) (hypodermis – hyaline layer – scelerides) o Fragments of Embryo containing aleurone grains o Fragments of epidermis containing mucilage Pigment layer Pigment layer Cross layer Cross layer Cross layer Cross layer Endosperm Embryo Chemical test (for cyanogenic glycoside Linamarin) (Guignard’s test)  Mechanism of reaction - Powdered plant material + dil. Sulfuric acid Hydrogen cyanide (HCN) will evolve - HCN will react with the sodium picrate in the filter paper giving sodium picramate - The reaction can be summarized in this equation: O Na O Na H2N NO2 O 2N NO2 NO2 NO2 HCN Sodium picrate Sodium picramate