Angiosperms

Characteristics:
Angiosperms are vascular, seed plants, that can be found everywhere.
Development and Life Cycle:


The plant’s life cycle and reproduction cycle are as follows:

• Anthers contain microsporangia, which contain misrosporocytes, which release microspores.


• Microspores form pollen grains, the generative cell inside of it will divide to form two sperm cells.


• Pollination occurs and the sperm are discharged into each ovule.


• Double fertilization occurs when one sperm fertilizes the egg and forms a zygote while the other combines with the two polar nuclei to form the nucleus of the endosperm.


• The zygote develops into an embryo that is packaged along with food in the seed.


• When the seed germinates the embryo develops into a mature sporophyte.

Notable Adaptations:


One adaptation of the Eschscholzia californica, or California Poppy, is the netlike veins that network through the leaves of the plant to provide better nutrient and water circulation.

Monocot versus Dicot


The Parts of the Plant

Roots:

The angiosperm has a root system,which could be either a tap root or a fibrous root which is dependent upon whether the plant is a monocot or a dicot.
Root System: the part of the plant, typically found underground, whose purpose is to anchor the plant to the ground, and absorb water and nutrients. The root system could be that of a tap root, or a fibrous root system.
Stems:
There is a stem present with vascular tissue that is scattered or in a ring pattern.

Flowers

The angiosperms have pollen grains and floral organs.
The flowers have:

• sepals that protect the flower from harm
  
• the petals, which are attractive in color to attract pollinators
  
• a stamen which contains the filament and anthers to give off the pollen
  
• and a carpel, which is the stigma, style and ovary, where the plant gets fertilized.

Plant Cells:
The three types of plant cells are the parenchyma, collenchyma, and sclerenchyma cells.
Parenchyma cells are the least specialized structurally, and perform most of the metabolic functions of the plant. Parenchyma cells synthesize and store various organic products. Photosynthesis occurs in the chloroplasts that are in parenchyma cells in the leaf,while parenchyma cells in the stems and roots have plastids that store starch. Fruit cells are mainly parenchyma (which is logical, as they store nutrients for the seeds).

A cross section of a Lily.

Collenchyma cells are grouped in strands or cylinders. They help support the young parts of the plant shoot. They have unevenly thickened walls. They lack secondary walls and the lignin is absent in the primary walls, which is why they allow flexible support without restraining growth.
Sclerenchyma cells are also used for support and have a thick secondary wall, strengthened by lignin. They are much more rigid than collenchyma cells. Mature sclerenchyma cells are not able to elongate, restraining the growth of the plant. There are two types of sclerenchyma cells, sclereids and fibers. Both are used entirely for support and strengthening.

Xylem and Phloem:
Xylem are the water conducting tubes of most vascular plants.
They contain tracheids, which are the tube-shaped cells that carry the water and minerals up from the roots.
Tracheids are actually dead cells, and only their walls remain to provide a system of microscopic water pipes.


Phloem are living sugar-conducting cells arranged into tubes that distribute sugars, amino acids and other organic products.


Plant Nutrition:
Plants have many minerals and compounds that are essential to their growth and reproduction.
This is where the root system comes into play, as it absorbs the water and nutrients the plant needs to grow.
Plants require several macronutrients such as:

• Carbon,
• Oxygen,
• Hydrogen,
• Nitrogen,
• Potassium,
• Calcium,
• Magnesium,
• Phosphorous
• and Sulfur.

They also require micro nutrients like:

• Chlorine,
• Iron,
• Manganese,
• Boron,
• Zinc,
• Copper,
• Nickel
• and Molybdenum.

A lack in any of these nutrients will cause the plant to be unable to run efficiently, and create several possible side effects, such as droopiness, or wilting.



Tissue Systems in Plants


There are three tissue systems in plants, which are the Dermal tissue system,the vascular tissue system, and the ground tissue system.
The dermal tissue system is the outer protective covering, like the skin of a plant, and it is the first line of defense against pathogenic organisms.

The vascular tissue system is the long distance transport system in the plant.
It is in charge of moving materials through the xylem and phloem.

The ground tissue system is the tissue that is neither dermal nor vascular.
If it is within the vascular tissue it is called the pith, and if it is external to it, it is called the cortex.
The ground tissue system contains cells that are specialized in photosynthesis, storage and support.

Plant Growth:

• Phototropism:
  Because of plant's reliance upon sunlight for the process of photosynthesis, plants have a tendency to grow towards a source of light (as shown by the peas in our classroom).
  This is called phototropism, which is when the plants shoot grows towards the source of light due to hormones and the angle of the light hitting the plant.
  Plants may also grow in response to gravity, which is called gravitropism; roots show positive gravitropism, and stems show negative gravitropism.
  
  
• Plant Hormones:
  There are six major hormones in a plant.
  
  
  
  • Auxin- which stimulates stem elongation, root growth and cell differentiation, and the development of fruit.
    
  • Cytokinins- Affected root growth and differentiation.
    
  • Gibberellins- Promotes seed and bud germination, stem elongation and leaf growth. Stimulates flowering and development of fruit.
    
  • Brassinosteroids- Inhibit root growth, retard leaf abscission.
    
  • Abscisic Acid- Inhibits growth, closes stomata during water stress.
    
  • Ethylene- Promotes fruit ripening, opposes some auxin effects; promotes or inhibits growth and development of roots, leaves and flowers.
    
  
  The Photoperiod
  
  The photperiod is the psychological reaction that organisms have to the length of day or night.
  Many flowering plants use a photorecptor protein to sense seasonal changes in night length, or photoperiod, which they take as signals to the flower.
  Certain plants may require a long or short enough night before they flower, while other are more likely to flower under the appropriate light conditions, but will eventually flower regardless of the photo-conditions.
  Day-length, and through day-length, the season of the year, is vital information to many species of plants, as it triggers several biological changes.
  There are plants that flower only on the long-days of the year, like summer, some that are short-day plants and some that are day-neutral.
  
  
  Flowering Plants and Their Reproductive System:
  
  Flowering plants reproduce through their flowers.
  Flowers are the sexual organs of plants and usually have a pollen system and ovaries, making them bisexual.
  Plants are pollinated by the wind or by bees and bugs and small animals, which then carry the pollen to the other plants, where the pollen goes through the style by a growth emitted from the pollen grain. The sperm travels through this pollen tube, eventually reaching the ovules and fertilization of the egg occurs.
  
  Defense Mechanisms of Plants
  
  Against Predators:
  Plants do a variety of things to defend themselves against disease or herbivores. When attacked by an herbivore, some plants can release a hormone that attracts the predator of that herbivore to defend itself.
  Against Pathogens:
  The dermis is the first layer of defense against pathogens.
  If an infection penetrates that barrier, the plant has a secondary defense: gene-for-gene recognition.
  The plant can recognize the pathogen and remove it.
  If that doesn’t work though, the plant can seal off the infected area or develop a systemic acquired resistance to provide against a diversity of pathogens for several days.