Monday, March 12, 2012

March 12, 2012

Hi everybody!

Today in class, we started off with measuring our plants (wild-type and rosette). For the rest of class we took notes on Chapter 28. Here are the notes (you should probably know the words in purple):

  • Stems - terminal bud is at apex of stem when plant stem is growing in length

  • Axillary buds, in angle formed by a leaf and stem, are dormant

  • Terminal bud produces hormones inhibiting growth of axillary buds = apical dominance, so plant can grow up to sun

  • Axillary buds begin growing and develop into branches under certain conditions

  • "Pinching back" is when you cut off the terminal buds, so the axillary buds grow (causing the plant to be bushy)

  • 3 kinds of modified stems:

  • Runner in a strawberry plant = horizontal stem - new plants emerge from tip of runner = asexual reproduction

  • Rhizome of an iris plant = horizontal underground stems = store food, & can bud new plants (where the plant comes up)

  • Tubers are rhizomes ending in enlarged structures (potatoes). Eyes of potato are axillary buds, can grow when planted

  • Leaves - flat blades (for light collection, move with light) and petioles (join leaves to stems)

  • Celery is a big petiole

  • Some plants have a multipart cell wall:

  • Primary cell wall - laid down first

  • Secondary cell wall - deposited between plasma membrane and primary wall, more rigid for support

  • Parenchyma cells - most abundant cell, for food storage, photosynthesis, have only primary cell walls

  • Collenchyma cells - provide support in growing parts of plant, have only primary cell walls

  • Sclerenchyma cells - have thick secondary walls (only type of cell out of these 3 that has secondary walls) with lignin (wood), when mature, most are dead - rigid cells support plants

  • 2 plant vascular tissues:

  • Xylem - contains water conducting cells - move water & minerals up stem

  • Phloem - contains food conducting cells - transport sugars from leaves or storage tissue to other parts of plant

  • 3 tissue systems continuous throughout plant:

  • Dermal - covers, protects, waxy coating (epidermis - like skin)

  • Vascular - xylem and phloem, support, transport

  • Ground - bulk of young plant, fills spaces between epidermis and vascular

  • Types of ground tissue:

  • Cortex - in root, cells store food, take up water & minerals

  • Endodermis - selective barrier in cortex (remember endo = inside)

  • Pith - fills center of stem in dicots, food storage

  • Stomata - in epidermis of leaf and some stems, are tiny pores between guard cells,

  • Minimizes water loss, allow gas exchange (should be open on a cool, humid day)

  • Mesophyll - ground tissue of a leaf, for gas exchange and photosynthesis, between epidermis and vascular tissue (remember meso = middle)

  • Review double fertilization:

  • Pollination

  • Pollen form 2 sperm

  • Sperm travel through a pollen tube to ovule

  • Double fertilization occurs: one sperm fertilizes egg forming diploid zygote which becomes the embryo; the other sperm joins to form the triploid central cell, which develops into endosperm, nourishing the embryo

  • Seed formation:

  • Embryo develops cotyledons (1 in a monocot, 2 in a dicot) - organs that absorb nutrients from endosperm

  • Embryo develops into mature seed with tough protective seed coat enclosing endosperm

  • Seed becomes dormant (time for seed dispersal, favors survival for good environmental conditions) until seed germinates

  • Fruit formation:

  • Fruit = mature ovary

  • Houses and protects seeds, disperses them from parent

  • Seed germination:

  • Seed takes up water and expands, ruptures seed coat

  • Embryo resumes growth (from dormancy)

  • Embryotic root emerges (grows downwards), then shoot; a hook forms near the tip for protection

  • True leaves expand from shoot tip and photosynthesize (sorry about the picture below...I know we don't know some of the words in there but the picture is still good!)

  • Plant growth:

  • Have indeterminate growth - continue to grow as long as they live - increases exposure to sunlight

  • Finite life span - 3 examples:

  • Annuals - mature, reproduce and die in 1 year or growing season

  • Biennials - live for 2 years; flower and seed occur during second year

  • Perennials - live and reproduce for many years

  • Primary growth - lengthening

  • Meristem - cells that divide and generate new cells and tissues

We stopped on page 15 of the notes...


  1. Work on your wildland project

  2. Chapter 28 study guide due Monday 3/19

  3. Study for the Chapter 16 quiz (either tomorrow or Wednesday)

Next scribe: Emily W


  1. Sorry about the spacing! It was acting really weird!

  2. This is a well done post with a lot of good information and helpful pictures. Good job!

  3. I agree, this was an extremely good post. The spacing did not bother me and i think the words that were bold were extremely helpful because i knew what to focus my attention on. Nice Job!