(peas)
Bark is the dead tissue of the stem that sloughs off or wears off, on the outside of the tree. Bark is different in the young stem than it is in the old stem. In the young stem, it is composed of phloem, cortex, cork, cork cambium, and epidermis. In the old stem, after the cortex and epidermis is gone, it consists of phloem, cork, cork cambium, and phelloderm.
The base is the bottom of a plant organ. It typically refers to a leaf and is the end to which the petiole attaches.
DIAGRAMS:
PHOTOS: Coprinus / Coprinus / Coprinus
DIAGRAMS:
DIAGRAMS: Plant Growth Cycles
PHOTOS:
DIAGRAMS: Biome Comparison
PHOTOS:
The blade is one of the structures that makes up a leaf. It is the flat expanded portion of the leaf. Leaf blade is synonymous with leaf lamina.
DIAGRAMS: Monocot Leaf
PHOTOS:
(marsileales and salvineales sporangia)
The border parenchyma are TRANSFER CELLS that cover the free open ends of the veinlets in the leaf. They look like parenchyma but function as transfer cells, picking up glucose from the leaf mesophyll, putting two glucose molecules together to form a sucrose molecule and then dumping the sucrose molecule into the sieve-tube member.
Bordered pits are pits that have the secondary cell wall extending over the pit with a small hole in the secondary cell wall to let the water pass through. When looking at a bordered pit under the microscope, it has the appearance of a donut. The hole of the donut is the pore and the outer ring of the donut is the margin of the bordered pit.
DIAGRAMS:
PHOTOS: Pinus Stem / Pinus Stem
DIAGRAMS: Biome Comparison
PHOTOS:
Many different plant entities branch in one way or another. However, when we talk of branching, we typically think of stems, rhizomes or trichomes that branch. There are several types of branching that refers to stems and rhizomes: dichotomous, monopodial, or sympodial. Branched hairs or trichomes are hairs that are not simple but branch in some way. For branching hairs we have no fancy terms that describe their branching that we feel is important to beginning botany students.
DIAGRAMS: Equisetum Stem
PHOTOS:
(hairs) (equisetum branches)
DIAGRAMS: Mustard Fruits
PHOTOS:
DIAGRAMS:
Bud scales are small scale-like structures that are modified leaves that cover the terminal bud during its winter dormancy. When the terminal bud breaks dormancy in the spring, these bud scales are shed, leaving the scars of where they were attached behind.
The scars left behind on the stem as the bud scales are shed in the spring when the terminal bud breaks dormancy. Because this happens only once during the year for each stem, it is possible to determine the age of a stem by noting the number of different clusters of bud scale scars on the stem.
DIAGRAMS: Woody Dicot Stem
PHOTOS:
Buds are small swellings or bumps on the stem around the node. They contain meristem tissue that when differentiated will become a particular plant organ such as a stem, leaf, or flower. Three types of buds exist, those that produce stems, others that produce leaves, and still others that produce flowers. They are therefore called leaf buds, flower buds, and stem buds. The stem buds are named for where they exist on the stem, apical or terminal if they exist at the top or end of the stem and lateral if they exist at the nodes below the terminal or apical bud. One other type of bud exists, known as adventitious buds. These buds arise at any place along the stem, generally in response to injury of the stem. It is a survival mechanism for the plant.
A bulb is a modified stem where the upper stem and the apical meristem are cover by several concentric layers of thick scales. The scales are modified leaves and swollen with water and stored food. Rootlets come out of the bottom of the bulb and are attached to the stem. A good example of a bulb is an onion.
DIAGRAMS: Bulb
PHOTOS:
DIAGRAMS:
A bundle cap is a a cluster of fibers that covers the top of the top or the phloem side of the vascular bundle.
DIAGRAMS: Monocot Stem
PHOTOS: Leaf Cross Section / Leaf Cross Section
Puccinia in Wheat / Monocot Stem
A bundle sheath can be two different structures depending upon the kind of cells that make up the bundle sheath.
If the bundle sheath is make up of fibers, then it surrounds the entire vascular bundle (usually a monocot vascular bundle), adding strength to the vascular bundle and the stem.
If the bundle sheath is made up of cells that look like parenchyma cells, then the bundle sheath surrounds the veinlets in the mesophyll of the leaf and function as transfer cells. They take glucose from the surrounding mesophyll, hook two molecules of glucose together to make sucrose, and dump that sucrose into the sieve-tube member.
DIAGRAMS: Hydathode
PHOTOS:
Within the outline of the leaf scar there will be bundle scars, the scars of the vascular bundles that attached the leaf's vascular system to the vascular system of the plant.
DIAGRAMS: Woody Dicot Stem
PHOTOS:
(leaves)
