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...

Homework:

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