Leaf Anatomy

Meristems
View of a shoot apical meristem with some leaf primordia.  Additionally, I have labelled the 3 primary meristems you can differentiate here.

Here's a nicotine leaf to show the two kinds of meristems specific to the leaf.  The leaf apical meristem becomes the midrib of the leaf, while the leaf marginal meristem is the blade of the leaf.

Epidermis
From a Sedum (stone crop)- you can see the "regular" epidermal cells (squiggly shaped) as well as the guard cells in various places surrounding stomata.

 Take a closer look:

Also here is a sunken stomate as seen in a Pinus leaf.  It is "sunken" because the guard cells are below the level of the epidermis which helps protect against dessication (drying out).

Mesophyll
Mesophyll just means middle of the leaf.  It is the term for the ground tissue in the leaf.  There are two types by shape: palisade and spongy.
You can see both of these well in a pine leaf:

We also term a leaf to be unifacial or bifacial based on the arrangement of the mesophyll.  Bifacial is if there is spongy on one side, and palisade on the other.  Unifacial is either the same type throughout, or it makes a kind of sandwich with the same kinds on either side and something different in the middle.  You can see this type of unifacial in a Dianthus (carnation) leaf:

(The red rod-shaped parts are palisade, the lighter stained area in the middle with a lot of spaces is spongy.)

Pine anatomy
Some things we learned specifically with pine needles (I'm not sure if they also apply to some other plants, sorry) are the resin duct with epithelium, hypodermal sclerenchyma, and transfusion tissue.
Some of these are labeled:

The outermost layer surrounding the resin duct is the epithelium.  Hypodermal sclerenchyma is below ("hypo") the outermost layer of cells or dermis.  These have thick secondary cell walls which add to the strength of a pine needle, as you have probably tested yourself many times when you got poked with one.  In this repeat picture you can see the hypodermal sclerenchyma with the thick red-stained walls, on either side of the sunken stomate.

Bundle Sheaths
Bundle sheaths are different in C3 plants and C4 plants.
Here, in a C3 grass (Poa), you see their regular bundle sheaths:

Closer.  Just looks like a blank set of cells surrounding the vascular bundle.

But in a C4 plant, like this Zea corn, the sheaths have what is referred to as "Kranz anatomy".  Kranz is German for wreath, and you can see they are rather leaf-like in the following examples. There are two orientation pictures, then it zooms in one a single bundle sheath so you can see the Kranz anatomy.

Leaf Abscission Zone
When a plant loses its leaves, it prepares for this by creating an abscission zone so the leaf can easily fall off without damaging any of the other tissue.  Layers of cells secrete suberin (or is it subirin?) for protection (and are called suberized cells), while the next outermost layer of cells is pre-programmed to break easily, as it were.  The weak layer is called the separation layer.

Whew, that's a lot of leaf anatomy!  Stay curious.


P.S. There are no picture source references cause I took all these with my camera (through the microscope in Botany lab) and did the labeling myself.

Plant Cell Wall Lab

In this lab we explored various anatomical features of plant cell walls.

Mitosis & Cytokinesis
Not going to repost that, I did this last year and it is still beautiful: Mitosis post
Here's another great pic of a cell plate and phragmoplast on the edges I got today though:

Cytokinesis in plants is a rather involved process since a new middle lamella must be made, followed by primary wall and sometimes secondary wall.


Primary pit fields
This is a TERRIBLE picture taken of a picture shown to me on another camera.  But you can kind of see the primary wall and the thinner parts that indicate the primary pit fields (pointer is on the thicker part of the primary cell wall).

More primary pit fields from a more 3D outside view of the cell (this is from #6 of the lab).

The cell walls are stained pink and you can see that there are lighter/ white spots on it.  That's where the wall is thinner, so those are the primary pit fields.

Plasmodesmata
By definition, plasmodesmata are only in primary cell walls, and they are channels between adjacent cells, through which the cytoplasm of each cell is continuous.  These occur more often in primary pit fields where the membrane is thinner, but they can happen anywhere in the primary wall.

You can also see these in the tomato cells we looked at last week:

Intercellular Air Spaces
These get formed often at the edges of cells as they are dividing, and are important to gas exchange for the plant. (#6)

Secondary Cell Wall
Here you can see the distinction between the secondary wall and the compound middle lamella (which includes middle lamella and 2 adjacent primary walls).

Just a picture to orient- vascular bundle, and the bundle cap at the top.

The lighter lines between all the cells are the compound middle lamella, the darker parts are secondary cell wall.

Pits
These are pear stone cells, and they have many long simple pits running through their secondary cell walls.  I thought they look rather similar to plasmodesmata, but the distinction is plasmodesmata are ONLY in primary walls, and pits are ONLY in secondary walls.  (Lab #9)

Bordered pits
Bordered pits from above look like little donuts.  Here there are a whole bunch in some dense pine wood.  These types of pits are common in water conducting cells, and they act to help prevent clogs from air bubbles. (Lab #11)

Stained microscope slides are pretty.  That is all.

Stay curious.