Botany: Sexual reproduction in flowering plants

Hilum

A critical point on the ovule where it connects with the funicle, playing a significant role in the ovule's attachment and nutrient transfer.

Sporoderm

The intricate protective cell wall of pollen grains, comprised of two layers: the exine (outer) and the intine (inner).

Exine

The robust outer layer of pollen grains, constructed from sporopollenin, known for its exceptional durability and resistance to degradation.

Intine

The delicate inner layer of the pollen grain wall, formed from cellulose and pectin, providing internal support and structure.

Sporopollenin

Considered the most resilient organic compound, it forms the exine of pollen grains, effectively protecting them from environmental extremes.

Pollen viability

The specific duration during which pollen grains maintain their ability to successfully germinate upon reaching the stigma of a flower.

Cryopreservation

An advanced technique involving the preservation of pollen grains at extremely low temperatures, utilizing liquid nitrogen to extend their viability for future fertilization.

Vegetative cell

The larger component of a mature pollen grain, characterized by abundant food reserves essential for supporting pollen tube growth.

Generative cell

The smaller yet crucial cell found within a mature pollen grain, responsible for dividing to form two sperm cells needed for fertilization.

Cleistogamy

A reproductive condition in which flowers remain closed and do not open, ensuring self-pollination without reliance on external pollinators.

Geitonogamy

A form of pollination that involves the transfer of pollen between two flowers that are located on the same plant, promoting genetic similarity.

Xenogamy

The process of pollination in which pollen grains are transferred from one plant to a different plant, facilitating genetic diversity and hybrid vigor.

Antipodal cells

Cells situated at the chalazal end of the embryo sac, typically degenerate as development proceeds, reflecting their non-essential role post-fertilization.

Apocarpous pistil

A type of pistil composed of carpels that remain distinct and separate from one another, allowing for independent development and fertilization.

Syncarpous pistil

A pistil formed from fused carpels, creating a unified structure that allows for a collective development of ovules.

Polar nuclei

Two nuclei located centrally within the embryo sac that unite during fertilization in a process termed triple fusion.

Specialized cells positioned at the micropylar end of the embryo sac, which play a supportive role in guiding the pollen tube towards the egg cell.

Synergids

Zygote

The resultant diploid cell formed when a male gamete successfully fertilizes an egg cell, marking the beginning of a new organism.

Triple fusion

A critical process in fertilization, wherein a male gamete fuses with two polar nuclei to create a triploid primary endosperm nucleus, vital for nourishing the developing embryo.

Endosperm

The tissue formed within seeds that surrounds and provides essential nutrients for the developing embryo, playing a key role in seed viability.

Dormancy

A physiological state in which the seed embryo remains inactive and unable to germinate until specific environmental conditions are met.

Germination

The transformative process wherein a seed transitions into a seedling, necessitating favorable environmental conditions, such as moisture and temperature.

Polyembryony

A phenomenon where multiple embryos develop within a single seed, allowing for increased chances of successful propagation.

Cleistogamous flowers

Flowers characterized by their inability to open, ensuring self-pollination and gene preservation in stable environments.

Nectaries

Glandular structures present in flowers that secrete nectar, an attractant for pollinators, thus enhancing the likelihood of successful pollination.

Orthotopes ovule Examples: Piper, Polygonum, Cycas.

Ovules that have their micropyle, chalaza, and funicle aligned in a straight configuration; they represent the most primitive form of ovule. Give examples

Anatropous ovule Example: most angiosperms. 82%

A type of ovule positioned at a 180° angle, so the micropyle is in proximity to or aligned with the hilum; Give example

Hemianatropous ovule Example: Ranunculus.

Ovules that display a 90-degree angle between the funicle and the body; they are somewhat intermediate in form. Give examples

Campylotropous ovule

Example: Cruciferae. luciferea

Ovule is curved more or less at right angle to funicle. Microplar end is bend down slightly Give examples

Amphotropus ovule Example: Lemna, Alisma. Poppy

Ovules where both the ovule and the embryo have a horseshoe shape; this form is less common. Give examples

Circinotropous ovule Example: Opuntia and Plumbaginacea

Ovule turns more than 360 degree angle. Give examples

Miotic division

The formation of haploid microspores from diplois mother micrspores is known as

Miotic division

The process of formation of vegetative and generative cells from microsporangia is known as

Polygonum, Oenothera

Exmple of monosporic embryo sac

Allium, Endymion

Example of bisporic embryo sac

Adoxa, Plumbago

Example of tetrasporic embryo sac