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Growth & Development

Grow lights Grow lights initiates plant growth A grow light or plant light is an artificial light source, generally an electric light, designed to stimulate plant growth by emitting an electromagnetic spectrum appropriate for photosynthesis. In winter, when the available hours of daylight may be insufficient for the desired plant growth, grow lights are used to extend the amount of time the plants receive light. The growth of plants depends on the amount, type and duration of light they are exposed to. Red and blue light are best for plant growth. Blue light encourages leaf growth, while red and blue light combined encourages flower growth. Let's explore more about plant growth and development.

Learning Objectives

After completing the topic, the student will be able to:

  • Define the term “meristem” and analyze how meristems help to increase the length and girth of the plant.
  • Identify the tissue systems of plants and explain their respective functions.
  • Describe and discuss the role of xylem and phloem in vascular plants.
  • Contrast the types of growth arising from apical and lateral meristems.
  • Explore how does the vascular tissue system enable leaves and roots to combine functions to support growth and development of the whole plant.
  • Describe and examine the tissue organization of stems and leaves that enable them to perform their functions.
  • Define “secondary growth” and analyze the functions of of vascular cambium in secondary growth.
  • Explore the role of cell division, cell differentiation and morphogenesis in plant growth and development.
Plant tissues Plant tissues Buttercup root. Light micrograph of a section through the root of a buttercup plant (Ranunculus sp.). The root contains a central vascular bundle (within blue circle), comprising xylem (blue/green) and phloem (pink) tissues. Xylem is responsible for transporting water from the roots upwards to the rest of the plant. Phloem carries sugars and other nutrients from areas that produce them (such as leaves) to those that require them (such as developing fruits).
Growth and Development

Plant Tissues
To succeed and grow simultaneously in two entirely different environments – air and soil – requires a myriad of adaptations, starting with cellular modifications into specialized kinds of tissues (groups of similar cells that are organized in a structural and functional unit) followed by development of organs (structures composed of several kinds of tissues grouped in a structural and functional unit).

The organs of a plant are comprised of three basic tissue systems, including the dermal, vascular, and ground tissue systems . These three motifs are continuous throughout an entire plant, but their properties vary significantly based upon the organ type in which they are located. Now we look at the structure and arrangement of plant tissues and cells in mature plant organs.

Cells of a plant or an animal acquire a variety of shapes and structure for specific functions they perform. They do so in groups called tissues. Tissue is a group of cells with a common function, structure or both. All cells of a tissue have common origin. Tissues can be simple, consisting of a single cell type, or complex, consisting of more than one cell type.

Plant Tissues: These are basically of two types–

1.Meristematic tissue and
2.Permanent tissue.

Meristematic tissue Meristematic tissue Longitudinal section through the top of a terminal shoot from a huckleberry (Gaylussacia baccata). The pale pink cells at bottom are stem cells that are undergoing elongation and vacuolization (becoming filled with vacuoles, which are fluid-filled cavities). The smaller and darker pink apical meristem cells towards the top are undergoing mitosis and have fewer vacuoles but denser cytoplasm. Surrounding the apical meristem and stem cells are leaf primordia (young leaves).
Meristematic Tissues

Meristematic tissue or Meristem: Plants are capable of indeterminate growth because they have perpetually embryonic tissues called meristems. Cells of meristems divide continuously and help in increasing the length and girth of the plant.

This tissue is found at all growing points of a plant, such as the tips of roots, stems and branches. It is also present between the bark and the wood of trees where it leads to the growth in the diameter of the stem. Main characteristics of meristematic tissue are as follows:

  • The cells are small.
  • The cells are similar in structure and are usually cubical.
  • The cell walls are thin.
  • Dense and abundant cytoplasm.
  • Single large nucleus.
  • Vacuoles almost absent.
  • Cells tightly packed with almost no intercellular spaces.
  • The cells actively divide adding new cells to the plant.
  • New cells thus produced are transformed into mature permanent tissues.
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