• food transport
• positive pressure system
• living cells filled with cytoplasm and nutrients
• sieve tubesray parenchyma & libriform fibers

• in phloem
• transports carbs and sugars, has no nucleus but companion cell does

• water conducting
• water conducting cells are dead at maturity
• tensil strength (rasing water upward through roots)
• rapdily moving 
• tracheids

• has 4 points of xylem (tetrarch)
• where secondary growth occurs (between xylem and phloem)

understanding the roles of regions in the apex by:

• creating mutants 
• analyzing natural mtuants 
• grafting cells from one plant to another 

(this all tracks developmental fate)

• Shoot Apical (SAMS)
• Root Apical
• Axillary
• Lateral
• Specialized 
• Intercalary
• Primary Thickening
• Plate
• Marginal

• Histogen theory
• Tunica Corpus theory
• Structured Apex thoery

• L1: produces epidermis
• L2: central regons of leaf that are photosynthetic
• L3: central region that produces vascular tissues & pithe

in order to understand the role of different regions of the apex, scientists have tried to follow the fate of the different layers, and sometiems individual cells in the apex 

(usually by creating or finding mutants / grafting cells)

• organized around controlled uptake of nutrients (specifically phosphorous)
• phsyiological sheath
• root cap
• mucilage
• stele at center (w/ endodermis and pericycle)

• 1 cell thick
• where lateral roots originate

• conducts photosynthesis
• creates negative pressues in water conducting xylem
• has both grana and stroma lamallae in chloroplasts

• little membrane-bound stacks 
• creates oxygen in PS2

• invaginations within chloroplasts that support grana

• layer of cylindrical sausage-like cells that photosynthesize betwen the epidermis and mesophyll
• filled with chloroplasts

• intercepting photons
• collection of CO2 
• transpiring water
• collection of photosynthates

• what most grasses go through
• Kranz anatomy 

• bundle sheath cells arranged in a "wreath" around vascular bundles 
• no grana, just stroma lamellae
• no PS2

• when a phton hits this, you get an electron raised to a  higher energy level
• oxygen and hydrogen are produced (where oxygen comes from)

• loading sugars into sodium sieve-tubes
• pressure gradient is caused, moves contents of sieve tubes from source to sink 

• located under bark
• photosynthetic
• absorbs CO for photosythesis

• Inside bordered pits
• when cell loses its negative pressure, the lack of negative pressure will drive the Taurus over to seal the opening, thus preventing an embolism of air 

• female
• forms the megaspores after meiosis that later develop into the megagametophyte (the eggs)

• male
• forms microspores after meiosis which develop into pollen grains

• phyllotactic structure, produces whirls of primordia that form the organs within a plant (carpals at the center, stamens, stepals, petals, etc)
• flower functions as a PR device

• fern gametophyte life cycle starting as haploid then becoming diploid ( a life cycle divided into two halves)

• Animals have predetermined germ cells that they are born with, and they are already differentiated
• vegetatively growing plants do not have this, so they produce differentation via the flowering meristem that forms eggs in the ovule and sperm in the pollen grains through meiosis 
• all occurs in the sporangium

• the structures where reproductive differentiation occurs
• germ cells are formed here

• when plants first emerged on land they had no leaves
• have photosynthetic stems and sporangia
• primitive stele in the stem with phloem-like and xylem-like cells 

• male produces pollen
• female produces eggs

• creation of the male gametophyte
• flower opens: pollen is carried to stigma, grows down the style, fertlizes the ovule

• 4 seperate sporangia that are fused into a single anther
• have sporangial wall cells on the outside, all cells are diploid paternal when the bud is still closed 
• microspore mother-cell

• Male gametophyte
• adheres to cell wall and creates the two sperm cells 

• arise on placental tissue 
• tiny meristematic bumps attached by a small stalk
• small stalk has a vascular bundle to carry nutrients 

• 4 megaspores
• 3 degenerate, the 1 surviving will divide (each nucleus is haploid)
• those then undergo two more divisions to produce 8 nuclei

(all occurs through meiosis)

• pollen tube enters through micropyle
• releases two sperm cells
• one enters through on esynergid, then enters the egg cell to form the zygote
• other synergid dissolves, second sperm cell fuses with the 2 polar nuclei in the female megagametophyte to form the embryo sac 

• formed by 2 polar nuclei and one sperm cell
• assists in nourishing the zygote

• first apical meristem
• cotelydons begin to grow visible

• cotelydons become more elongated

• primordia within the early embryo, two branches that originate from suspensor and develop form hypophysis