1. Notes: Seeds

2. What is a seed? A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. The formation of the seed completes the process of reproduction in seed plants.

3. Why are seeds advantageous for plants? maintain dormancy until better environmental conditions arise afford protection to young plant at vulnerable developmental stage contain adequate food supply until photosynthesis is possible dispersal of plants

4. Skill: draw internal structure of seeds

5. SEED STRUCTURE External Seed coat (testa) Hilum Embryo Cotyledon Epicotyl / Hypocotyl Pumule Radical

6. Seed Coat AKA testa The seed coat protects the embryo Can be of varying thicknesses, depending on the seed type.

7. Hilum Scar from the seed being attached to the parent plant

8. Embryo The embryo is what forms the new plant once the opportune conditions are present.

9. Cotyledon The cotyledon is the first leaf that germinates. It is filled with stored food that the plant uses before it begins photosynthesis. Some plants have 1 cotyledon (monocot) and some have 2 cotyledons (dicot).

10. Epicotyl /Hypocotyl The basis for the plant’s stem. It is known as the epicotyl above the cotyledon and a hypocotyl below the cotyledon. These grow upward in response to light.

11. Plumule The shoot tip with a pair of miniature leaves.

12. The Radicle The part of the seed where the root develops.

13. SEED STRUCTURE Seed coat (testa) Embryo Cotyledon Epicotyl / Hypocotyl Pumule Radical

14. SEED DISSECTION MATERIALS Soaked pinto seed Dissecting microscope Tweezers Ruler

15. SEED DISSECTION EXTERNAL Draw the external pinto bean Label structures from notes INTERNAL Carefully remove the seed coat. Gently pull apart the two halves of the seed. Examine each half with the dissecting microscope Draw what you see inside the bean Label structures from notes REVIEW THE RULES FOR LAB DRAWING IN YOUR STUDENT GUIDE BE SURE YOU MEASURE AND RECORD THE LENGTH OF YOUR SEED

16. Plumule Cotyledon Embryo Hypocotyl Epicotyl Radicle

17. Germination After seed is formed, dehydration occurs until water is only about 10-15% of its weight Seed becomes dormant When conditions become right, the seed will begin to develop into a functional plant

18. Initial process in seed germination The absorption of water Release of a plant growth homorne – gibberellin (gibberellic acid) Gibberellin causes production of amylase, which hydrolyses starch into maltose Maltose is further hydrolysed into glucose, which can be used in cellelar respiration The early glucose may also be converted into cellulose to make new cell walls

19. Germination The development of the seed into a functional plant.

20. Steps to the emerging plant 1 st organ to emerge = radical (seed root) The shoot tip must break through the soil surface In many dicots, a hook forms in the hypocotyl & growth pushes the hook above ground Stimulated by light, the hypocotyl straightens, raising the cotyledons & epicotyl The epicotyl now spreads its 1 st foliage leaves They will begin doing photosynthesis

21. Water Uptake water = imbibition The seed expands and ruptures the testa (seed coat) Gibberellins signals enzymes to begin digesting stored material in the endosperm GA triggers the formation of a-amylase that hydrolyzes starch in the seed

22. Oxyen A-amylase breaks down storage sugars Converts them to other forms the seed can use If soil is waterlogged, it might cut off necessary oxygen supply and prevent the seed from germinating.