LAB 2

LEAVES

• one of the three organs of plants
• contains the photosynthetic material
• many, many forms of leaves exist
• general structure includes: epidermis, vascular system and "filler" ground tissue
• three main parts of the leaf include: base, petiole, and blade

My very artistic diagram of the main parts of a leaf.





Here is a cross-section of a leaf (live material).
The fibres are stained with toludine blue so you can easily see them.


This prepared slide shows the two mesophyll layers very nicely. The palisade mesophyll is where the majority of the photosynthesis occurs.

Can you explain the organization of the palisade mesophyll layer? Think about their cell shape, and how tightly they are packed together. Compare this with the spongy mesophyll, why is one layer less tightly packed?




Here is another cross section through live material (Lonicera), can you identify A B C and D?



Here is a section through a monocot leaf, this is Phormium tenax or New Zealand flax or hemp.
The white circles show the many structural (aka hard) fibres found in monocots.
The red circles show the vascular bundles.




The goodies inside our pitcher plant. Why do pitcher plants bother catching insects? What does this tell you about the importance different chemicals in soil?



Leaves come in a variety of shapes, sizes and forms. Please see the link below for more information about the different forms of leaves, the diagrams are extremely clear, concise and accurate. There is hardly any description (no big words), so it's a good site if you just want a quick and dirty way of learning about plant structure.

http://www.vplants.org/plants/glossary/plate02.html

Can you think of useful ways in which humans utilize leaves? If you have any interesting facts please comment and share with us.



ROOTS

• one of the three organs of plants
• contains the starch storing cells
  
• many roots hairs which pull water and nutrients into the plant root
  
• general structure includes: epidermis, cortex, endodermis, pericycle, phloem and xylem
  
• roots of large plants often form symbiotic relationships with mycorrhizal fungi

This diagram illustrates the different parts of a primary root visible in a longitudinal section.
Note that "vascular cylinder" is synonymous with "stele".

What is the root cap and why is it so important to plants?



This diagram shows a common garden bean germinating into a seedling.

What is the function of the cotyledons?

Raphanus seedling root. Notice the lateral branching off the main root.



Zooming in on the lateral branches and main stem the root hairs become apparent.
These root hairs are responsible for the abortion of water through the soil.



This is a cross section through a primary root.

Can you name the functions of all the labeled parts?



A cross section through a root in which a lateral root is beginning to emerge from the pericycle.

Is this a primary root or a secondary root? How can you tell? Does lateral branching involve the forming of secondary xylem or phloem?

Roots can often be highly modified. The roots Shona is holding in this picture are in fact sweet potatoes.

Can you imagine what kind of chemical these roots are modified to store?

WITHOUT scrolling back up can you label A B C and D?

Feel free to post answers to the questions and / or discuss them by posting comments.