Plant Biology: Reproduction and Physiology

Ruminate endosperm is commonly found in the seeds of Annonaceae. 

The growth of a pollen tube toward the ovule is an example of chemotropism - movement in response to chemical stimuli. The ovule releases chemical signals (specifically calcium ions and chemotropic factors like LURE peptides) that guide the pollen tube's growth. This ensures precise delivery of sperm cells to the embryo sac for fertilization.

In Brassica campestris (mustard plant) and most angiosperms, the endosperm is triploid (3n). This results from double fertilization, where one sperm fertilizes the egg (forming a 2n zygote) and the second sperm fuses with the two polar nuclei (each n), creating a 3n endosperm that provides nutrition to the developing embryo.

In unisexual plants, sex expression can be modified by applying plant growth regulators, particularly auxins and ethylene. These hormones can influence the development of male or female flowers. For example, applying auxins or ethylene often promotes femaleness in certain species, while gibberellins may promote maleness.

Syngamy is the process of fusion of two gametes (male and female) to form a diploid zygote during the process of fertilization.

In angiosperms, the pollen grain produces two male gametes. One fuses with the egg cell to form the zygote, and the other fuses with the central cell to form the endosperm.

Trofim Lysenko, a Soviet agronomist, is credited with describing the phenomenon of vernalization, which is the induction of a plant's flowering process by exposure to prolonged cold.

In a typical sigmoid growth curve, the exponential phase (or log phase) is characterized by the most rapid rate of growth as resources are abundant.

Malacophily is a type of pollination where snails or slugs act as the pollinating agents for flowers.

Vernalization is the process where flowering is induced by exposing plants to prolonged cold temperatures. It is a common physiological response in many winter annuals and biennials.

The Richmond-Lang effect refers to the delay of senescence in detached leaves by the application of cytokinins. Kinetin is a well-known synthetic cytokinin.

Nastic movements are non-directional responses to stimuli, such as the opening and closing of flowers in response to light or temperature changes. Unlike tropic movements, they do not depend on the direction of the stimulus.

Double fertilization is a characteristic process in angiosperms where one male gamete fuses with the egg to form a zygote, and the other fuses with the secondary nucleus to form the primary endosperm nucleus.

Pollination is the transfer of pollen grains from the anther to the stigma, a process characteristic of seed-bearing plants, specifically Angiosperms and Gymnosperms.

Entomophilous (insect-pollinated) flowers typically have sticky and rough pollen grains to ensure they adhere to the bodies of visiting insects.

Yucca plants have a highly specific, obligate mutualistic relationship with the Pronuba moth, which is the only agent that pollinates the Yucca flower.

Blastophaga grossorum is a species of fig wasp that is essential for the pollination of Ficus species, specifically the common fig.

Garner and Allard are the scientists credited with the discovery of photoperiodism, which is the physiological reaction of organisms to the length of day or night.

Geitonogamy is the transfer of pollen from the anther of one flower to the stigma of another flower on the same plant. Genetically, it is self-pollination (same genotype), but ecologically, it is cross-pollination (requires a pollinating agent).

The fusion of one male gamete with the two polar nuclei (or the secondary nucleus) results in the formation of the primary endosperm nucleus (PEN), which is triploid.

Entomophilous flowers are adapted to attract insects, so they are typically brightly coloured and scented to act as signals for pollinators.

Pollination by ants is specifically referred to as myrmecophily.

Maize (corn) is a classic example of a plant that relies on cross-pollination, typically by wind (anemophily), to ensure genetic diversity.

Herkogamy (physical barriers), Dichogamy (temporal separation of sex organs), and Self-sterility (genetic incompatibility) are all mechanisms that prevent self-pollination.

Porogamy is the most common type of fertilization in angiosperms, where the pollen tube enters the ovule through the micropyle.

Cleistogamous flowers are bisexual flowers that never open, ensuring self-pollination. This is a reproductive assurance strategy. Homogamous means all flowers in inflorescence are same sex/age. Heterogamous means different types of flowers in inflorescence. Dichogamous refers to timing of sex organ maturity.

The translator mechanism is a specialized pollination apparatus found in the family Asclepiadaceae, with Calotropis being a prime example.

The Avena curvature test is the classic biological assay used to detect and quantify the presence of auxins based on the growth response of oat coleoptiles.

Gibberellins are plant hormones known for promoting stem elongation, which can overcome genetic dwarfism in certain plant varieties.

The liquid inside a green coconut is known as liquid endosperm, which contains free nuclear endosperm.

Geitonogamy is the transfer of pollen from one flower to another on the same plant, meaning the genetic material is identical.

Parthenocarpy is the development of fruit without fertilization, leading to seedless fruits. It is commonly observed in commercial banana varieties.

Salvia flowers exhibit a specialized lever mechanism where an insect entering the flower pushes a lever that deposits pollen onto its back.

Parthenocarpy is the specific term for the formation of fruit without fertilization, resulting in seedless fruit.

Hydrophily is pollination by water. Vallisneria is a classic example of a submerged aquatic plant that uses water currents to transport pollen to the female flowers.