Parts of a flowerThe four kinds offloral organs arethe sepals,petals, stamens,and carpels. epals and petals are Snonreproductive organs. tamens and carpels Sare the male and femalereproductive organs,respectively.
The stamen he microsporangia/pollen T sacs contain the pollen grains made up ofanther and filament
The stamen: tissue differentiation endothecium 10 parietal layer **middle layer TapetumArchesporial * (nourishment of the developing PMC) layer Meiosis*** 10 sporogenous Micro microspores tissue sporocytes *periclinal division **in eudicots originate from outer parietal layer; in monocots from inner parietal layer ***cytokinesis is usually simultaneous in dicots and successive in monocots
Illustration of a new models for plant archesporial initiation in theovule and anther.Cells colored in red, blue, yellow, magenta, orange and greenindicate archesporial cells, sporogenous cells (sc), primaryparietal cells, tapetal cells, middle layer cells and endotheciumcells, respectively.
Pollination and FertilizationPollination – is the transfer of the pollen to the stigma of the flowerSelf pollination – transfer within the same flower or between flowers of the same plantCross pollination –transfer to a genetically distinct flower Double fertilization gives rise to the zygote and endosperm • ndosperm development usually E precedes embryo development.
Endosperm he endosperm is rich in nutrients, which it provides to Tthe developing embryo. n most monocots and some eudicots, the endosperm I also stores nutrients that can be used by the seedling after germination. n many eudicots, the food reserves of the endosperm I are completely exported to the cotyledons before the seed completes its development, and consequently the mature seed lacks endosperm.
Embryo and suspensor he first mitotic division of the zygote is transverse, splitting the Tfertilized egg into a basal cell, and a terminal cell which givesrise to most of the embryo. he basal cell continues to divide transversely, producing a T thread of cells, the suspensor, which anchors the embryo to its parent.
Embryo and suspensor he suspensor pushes the embryo into the endosperm T he suspensor may develop into a large haustorium which T draws nutrients to the embryo from the parent he terminal cell divides several time and forms a spherical Tproembryo attached to the suspensor. otyledons begin to form as bumps on the proembryo. C -A eudicot, with its two cotyledons, is heart- shaped at this stage. -Only one cotyledon develops in monocots.
The embryo After the cotyledons appear, the embryo elongates. -Cradled between cotyledons is the apical meristem of the embryonic shoot. -At the opposite end of the embryo axis, is the apex of the embryonic root, also with a meristem. After the seed germinates, the apical meristems at the tips of the shoot and root will sustain growth as long as the plant lives. -The three primary meristems - protoderm, ground meristem, and procambrium - are also present in the embryo. During the last stages of maturation, a seed dehydrates until its water content is only about 5-15% of its weight. - The embryo stops growing until the seed germinates. - The embryo and its food supply are enclosed by a protective seed coat formed by the integuments of the ovule.
The Seed In the seed of a common bean, the embryo consists of an elongate structure, the embryonic axis, attached to fleshy cotyledons. - Below the point at which the fleshy cotyledons are attached, the embryonic axis is called the hypocotyl and above it is the epicotyl/ plumule, consisting of the shoot tip with a pair of miniature leaves. - The hypocotyl terminates in the radicle, or embryonic root.
The Seed While the cotyledons of the common bean supply food to the developing embryo, the seeds of some dicots, such as castor beans, retain their food supply in the endosperm and have cotyledons that are very thin. - The cotyledons will absorb nutrients from the endosperm and transfer them to the embryo when the seed germinates.
The Seed The seed of a monocot has a single cotyledon. - Members of the grass family, including maize and wheat, have a specialized cotyledon, a scutellum. - The scutellum is very thin, with a large surface area pressed against the endosperm, from which the scutellum absorbs nutrients during germination. The embryo of a grass seed is enclosed by two sheaths, a coleorhiza, which covers the young root, and a coleoptile, which cover the young shoot.
Types of seed germination 1. ypogeal germination H2. pigeal germination E