Plant structure and form
 

• The basic structures of a plant consist of a root system that is below the ground and a shoot system that is above the ground

• The five organs of plants include the vegetative components (roots, stems, and leaves) and the reproductive organs (flowers and fruits)
   

Root System

• The roots of the root system absorb water and minerals through small root hairs from the substrate on which they are growing.

• The roots transport the water and minerals to the vascular tissue through the xylem of the plant
   

Shoot System

• The shoot system of a plant consists of stems, which provide support, and leaves, the primary organs of photosynthesis. The terminal bud of the stem is the primary growing tip, located at the apex of the stem. This demonstrates apical dominance, a phenomenon in which the plant stem grows more strongly than side stems by pooling resources to promote elongation. Leaves primarily consist of vascular tissue embedded in ground tissue. They are enclosed by epidermal tissue
   

Types of plant cells:

• Parenchyma cells

  • thin, flexible cell walls and perform many of the metabolic functions of the plant

  • In the leaf, parenchyma cells are the site of photosynthesis, whereas in stems they aid in the support and storage

• Collenchyma cells

  • their cell walls have a varying thicknesses that provides structural support to younger areas of the plant, e.g. new shoots and leaves

• Sclerenchyma cells

  • primarily provide support. They have thick cell walls and are rigid due to the cellulose in their walls

  • Water-conducting cells

  • in the xylem aid in water transport

 

Plant Reproduction

Plants reproduce through a process called alternation of generations.  It's named this way because their life cycle alternates between a haploid organism and a diploid organism.  In more primitive plants such as mosses (bryophytes), the haploid phase involves a multicellular haploid being, which we don't see in animal life cycles!

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Angiosperm life cycle & double fertilization

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1. After a pollen grain (containing the microspores) is deposited on the stigma, it germinates and grows through the style to reach the ovule

2. A pollen tube cell extends down through the style to reach the embryo sac

3. The sperm fertilizes the egg cell, forming a diploid zygote; the other sperm fuses with the two polar nuclei, forming a triploid (3n) cell that develops into the endosperm, which becomes the zygote's nutrient source.   Together, these two fertilization events in angiosperms are known as double fertilization (very important to know)

4. After fertilization, the fertilized ovule develops into a seed, and the tissues of the ovary become the fruit, usually enveloping the seed.

5. Embryonic development is suspended for a while, and growth is resumed only when the seed germinates. The developing seedling will rely on the food reserves stored in the cotyledons until the first set of leaves begin photosynthesis