Leaves

Auxin

 A hormone that signals cell division in the apical meristematic tissue. Making it start the lateral protrusions, leaf primordium.

Leaf primordium

group of cells that will form into new leaves

Phyllotaxy

Determines how the leaves are organized. The meristematic location is based on types of ... Determines if the the leafs are opposite, alternate or whorled. 

Pinnately compound leaf

There is 1 rachis that is the area of 2dary branching off for the leaflets. 

Palmately compound leaf

the leaflets attach together

Divergent

the primary veins go out away from each other.

Convergent

The primary veins tend to go out together. 

pinnate venation

there is 1 primary vein called the midvein which is included within an enlarged midrib. 2ndary venation starts at the midvein

Palmately veined leaves

There are several primary veins that go from the base to the front of the leaf. 

Dichotomous venation

Venation without a midvien. Ex, ginkos

Epidermis

Usually a single layer of cells across the whole surface. The cells secrete a waxy cuticle. Used to provide protection. It can be found on the upper and lower parts of the leaf. 

Stomata

on the lower epidermis for the most part. They are absent from submerged aquatic plants. They are important for the regulation of gas exchange and evaporation of water from the roots. Opening/closing is dependent on the amount of water in the guard cells. Which is dictated by potassium. 

Mesophyll

It is in the middle and is where most of the photosynthesis occurs. 

Where the vascular bundles are found. 

Palisade mesophyll

Area of the mesophyll. Compacted parenchyma cells that are very stacked. It is 80% of the leaf's chloroplast and the main sight of photosynthesis. It is closer to the surface. 

Spongy mesophyll

 Area of the mesophyll. Loose parenchyma cells with lots of air space between cells. Found at the  bottom of the leaf. Making it closer to the stomata and the gas exchange. Having more space is better for the air "circulation"

Vascular bundels

 Are found throughout the mesophyll . Full of xylem and phloem surrounded by the bundle sheath. 

Bulliform cells

Found on either side of the central vein towards the surface they open and close to prevent desiccation,causing the lead blade to fold or roll. Common in grasses.

Rubisco

• Found inside the chloroplasts

• It is a Carboxylase and an Oxygenase enzyme.

Kranz anatomy

The mesophyll and bundle sheath are very stalked in structure and form 2 concrete layers around the veins. Only in 4-C.

Shade leaves

A response to their environment and where they are found in the canopy. They have fewer mesophyll layers, fewer chloroplasts. Leaves are larger to try and capture some light. 

Arid leaves

found in limited water conditions, thick leathery leaves, fewer stomata, few to no leaves at all. Similarly to pine trees they will have sunken stomata which can be found below the epidermis. Also can be covered in hairs.

Tendril

 adaptation of leaves to climb onto surfaces to get more sun. Ex, squash

Spines

sharp modification of the leaf, reduces water loss

Thorns

sharp modification of the branch/stem

Prickles

sharp modification of the epidermis. They are the easiest to remove

Succulent leaves

Can be found in the desert. Leaves are full of water. They have a lot of hydrenchyma cells, they are parenchyma cells with no chloroplasts and large vacuoles. 

Fleshy leaves

 Can be used to store é for rapid growth. Ex, onion

Reproductive leaves

each plantlet has a root system to perform vegetative propagation for asexual reproduction.

Floral leaves

bracelets, attracts pollinators. Ex, poinsettia