PLANTS AND PEOPLE - LECTURE NOTES
Hugh D. Wilson

REVIEW: PHOTOSYNTHESIS = LIGHT + H20 + CHLOROPLAST = O2 +H+ AND ENERGY (ATP), THEN: ENERGY IS USED TO 'FIX' CARBON [CO2] INTO HYDROCARBONS, MOSTLY POLYSACCHARIDES STARCH AND CELLULOSE. (WHAT DO THESE TWO HAVE IN COMMON? [GLUCOSE] - AND HOW DO THEY DIFFER? (LINEAR VS. LINKED - BONDING - SEE FIG. 10-9, P. 250]. Also, with regard to the question on Cellulose digestion in humans, it appears that we lack the required enzymes (cellulases).  These are only produced by 'hardcore' decomposing elements of the biosphere (fungi, bacteria, etc.) and mammals must evolve 'cooperative' systems (ruminants) to deal with cellulose digestion.  Rabbits have a large, pouch-like structure (cecum) that carries cellulase-producing bacteria and our G.I. tracts have a reduced cecum (with vermiform appendix), suggesting a similar set up in our phylogenetic past (vestigial - see overview), BUT herbivorious primates (Gorilla) are also (like Homo) not equipped to digest cellulose.  Since cellulose digestion is an active topic from an environmental point of view (re-cycling, biofuel), there is a lot of info on this topic available on the web.  Use a web search engine, like Google, to explore by inserting a series of words in the query box, in this case "cellulose digestion animal" will produce over 22,000 references with those most relevant to the 'set' of terms on the 1st page.  CAUTION:  web-based info comes in varying qualities - consider the source.
 

LAST TIME, TALKED ABOUT SHUNT OF 'PHOTOSYNTHATE' INTO VEGETATIVE PARTS OF THE PLANT [SHOOT, LEAVES AND ROOT]. MAN INTERVENES TO HARVEST BULBS, TAP/TUBEROUS ROOTS, TUBERS BEFORE THEY CAN BE USED BY THE PLANT.

NOW TIME TO LOOK AT THE DIRECT SHUNTING OF PHOTOSYNTHATE TO THE NEXT GENERATION TO FORM THE ANGIOSPERM EMBRYO AND ITS NUTRIENT SUPPLY - THE ENDOSPERM. UNIQUE TO FLOWERING PLANTS.
 


WHAT IS A FLOWER? - MODIFIED SHOOT. THUS, FLORAL PARTS ARE MODIFIED LEAVES.

 

FLOWER AS A MODIFED SHOOT - 4 FLORAL WHORLES - PHYLETIC ORIGIN OF THE STAMEN AND PISTIL (BASIC 301 APPROACH-FOCUS ON GYNOECIUM)
 

Lowermost two whorles are asexual:
 

1. CALYX 

2. COROLLA - POLYPETALOUS/SYMPETALOUS, REGULAR/IRREGULAR (FLOWERING PLANT TRENDS). DO WE EAT PETALS? (CUCURBITA and overview)

DIVERT=====to explanation:

Next two whorles are sexual - to understand these from both a functional and a structural point of view, must look at angiosperm evolution:

ALTERNATION OF GENERATIONS - MOSSES VS. ANGIOSPERMS - REDUCTION OF THE GAMETOPHYTE - FERNS

START OF ANGIOSPERM SEX:

SPOROPHYTE (DIPLOID - MEIOSIS - MICROSPORES/MEGASPORES - MICROSPORANGIA/MEGASPORANGIA)

GAMETOPHYTE (HAPLOID - MICRO AND MEGA)

ENDOSPORIC GAMETOPHYTE DEVELOPMENT (within spore wall)

DOUBLE FERTILIZATION/ENDOSPERM  (overview)
 
 

BACK TO STRUCTURE: Fertile fern frond - sporangia producing identical spores which germinate to produce identical, photosynthetic bisexual gametophytes (homosporus) - for angiosperm, imagine:
 


for the other, egg-producing sporangium, imagine:
 

3. ANDROECIUM - [STAMENS] DO WE EAT STAMENS? NO - (maybe Cloves - Syzygium aromaticum - Myrtaceae)

4. GYNOECIUM - WE EAT GYNOECIA - MEGASPOROPHYLL [GYMNOSPERM VS. ANGIOSPERM] TO CARPEL - SPECIALIZATION OF THE CARPEL [STIGMA (SAFFRON), STYLE, OVARY], SYNCARPY, SIMPLE PISTIL VS. COMPOUND


Return to Course syllabus
  25 Jan 2011