Primary growth is the lengthening of the stem and roots.
All plant growth occurs by cell division and cell elongation. Cell division occurs primarily in regions of undifferentiated cells known as meristems. The meristems make it possible for plants to have indeterminate growth.
Cell division in the apical meristems and subsequent elongation and maturation of the new cells produces primary growth.
Secondary growth is the increase in girth of stems and roots.
Cell division occurs in the lateral meristem; hence, this phase is also referred to as lateral growth
Angiosperms have flowers and bear seeds enclosed in a protective covering called a fruit
Angiosperms are further divided into monocots and dicots.
There are at least 250,000 species of angiosperms ranging from small flowers to enormous wood trees.
Pollination is accomplished by wind, insects, and other animals.
The male part is the pollen grain, and the female part is the ovary.
Characteristic Monocots Dicots Cotyledons (seed leaves) One Two Vascular bundles in stem Scattered In a ring Leaf venation Parallel Netlike Floral parts Usually in 3s Usually in 4s and 5s Roots Fibrous roots Taproots Additional Fewer than 10% of species are woody About 50% of species are woody
Petals: brightly colored, modified leaves found just inside the circle of sepals; attract animals that will pollinate the plant
Sepals: outermost circle of leaves; are green and closely resemble ordinary leaves; enclose the bud before it opens and protects the flower while it develops
Pistils or carpels: female part of the flower; produce the female gametophytes; each consists of an ovary, stigma and style
Ovule: the structure within the ovary where the ova (female gametophytes) are produced
Ovary: swollen part of pistil that contains the ovule, where one or more ova are produced
Style: long, usually thin stalk of pistil
Stigma: sticky top of the style where pollen lands and germinates
Stamen: male part of the flower, made up of anther and filament
Anther: male part of the flower where sperm (pollen) are produced by meiosis
Filament: threadlike structure that supports the anther
Gymnosperm vs Angiosperm Characteristics Gymnosperms Angiosperm Naked seeds X Seeds inside a fruit X Flowering plants X Produce cones X Produce fruits X Wind pollination X X Insect pollination X Examples Ginkgo, pine, redwood, hemlock, firs Corn, grasses, rose, tomatoes, apples
Plant hormones are also known as phytohormones . They are found in plants in very low quantities. Hormones help in different activities of a plant like flowering, senescence (aging) and ripening of fruits. Each hormone in a plant has a specific function to perform.
There are five hormones which help in different processes in plant growth and development. They are:
These are the plant hormones which carry out or help in cell division and stem elongation
Gibberellins also help in breaking the dormancy of seed and can delay aging and death of leaves and fruits
Work together with auxins to promote cell growth
Induce bolting, the rapid growth of a floral stalk. When a plant, such as broccoli, which normally grows close to the ground, enters the reproductive stage, it sends up a very tall shoot on which the flower and fruit develop. This is a mechanism to ensure pollination and seed dispersal
We define pollination as the transfer of pollens from anther to the stigma of the same flower or different flower.
Formation of fruits from flower depends on fertilization and this can be carried out only after pollination .
Types of Pollination:
Self pollination - There are a few plants which can pollinate themselves. This is transfer of pollen to the stigma of the same flower. Stigma is sticky and therefore receives the pollen easily. E.g. legumes, peanuts, tomatoes and peas
Cross pollination -This is a process in which pollen of one flower is transferred to the stigma of another flower. Plants which are adapted to cross pollination have taller stamens than carpels, so that pollens can spread and reach different flowers for fertilization.eg-pumpkins and cucumber.
Hydrophily -This is a rare form of pollination in which pollen reaches the stigma by the flow of water, so this is a transfer of pollen by water.eg-species of waterweed and pondweed.
Anemophily -This is a type of pollination where pollen is distributed by wind.eg-grass, conifers and chestnut.
When pollen grain of a flowering plant fuses with the ovule of a flower, it is known as fertilization. The pollen grain forms a pollen tube after reaching the stigma of a flower. This pollen tube grows down through the style and pierces one of the ovules. This process is known as fertilization.
It is a process in flowering plants during reproduction where two sperm nuclei from each pollen fertilize two cells of the ovary.
The gene combinations that result from a genetic cross can be determined by drawing a diagram called a Punnett Square
The types of gametes produced by each F 1 parent are shown along the top and left sides of the square
The possible gene combinations for the F 2 offspring appear in the four boxes that make up the square
The letters represent alleles
R = dominant and r = recessive. Combinations with the dominant trait will express that trait. What is the probability that the F 2 generation will have smooth peas? What is the probability that they will have wrinkled peas? What are the dominant and recessive traits?
Punnett squares can be used to predict and compare the genetic variations that will result from a cross
Organisms that have two identical alleles for a particular trait are called Homozygous (i.e. TT)
True-breeding for a particular trait
Organisms that have two different alleles for the same trait are called Heterozygous (i.e. Tt)
Hybrid for a particular trait
Phenotype refers to physical characteristics
Genotype refers to the genetic makeup
Example: pea plants can display the same phenotype (i.e. round pea shape), but have different genotypes (i.e. RR and Rr)
Which are the homozygous individuals and which are the heterozygous individuals? Which individuals display the same phenotype? Which display the same genotype? Which display the same phenotype and different genotypes?
Linked: if two genes are located near each other on the same chromosome, then the alleles for these genes will stay together during meiosis
Unlinked: the further apart the genes, the more recombination that will occur between them, and the less linkage that will be observed. Recombination frequency will display almost no linkage and assortment independently