SEED GERMINATION

 

INITIAL STEP IS IMBIBITION, THE UPTAKE OF WATER

 

WATER MOVES DOWN A WATER POTENTIAL GRADIENT AND IS DRIVEN BY MATRIX FORCES OR MATRIX POTENTIAL

 

      Y = YP +  YS  +  YM

 

 YM IS ALWAYS NEGATIVE

 

THE IMBIBING MATERIAL SWELLS CREATING A PRESSURE CALLED IMBIBITION PRESSURE

 

   PRESSURE CAUSES RUPTURE OF

   THE TESTA SO THE EMBRYO MAY    EMERGE

 

IMBIBITION CAUSES MANY BIOCHEMICAL REACTIONS TO OCCUR

 

  

1.   RESPIRATION INCREASES

 

2.   HYDROLYTIC ENZYMES DIGEST AND

   MOBILIZE STORED FOOD RESERVES

 

3.   RENEWED CELL DIVISION AND CELL   ENLARGEMENT

 

4.   GLYCOLYSIS AND CITRIC ACID    CYCLE ARE ACTIVATED 

 

5.   PENTOSE PHOSPHATE PATHWAY

 

GERMINATION IS CULMINATED WHEN THE RADILE EMERGES FROM THE SEED COAT.

 

SHOOT DEVELOPMENT

 

THE SHOOT AXIS ELONGATES FOLLOWING THE EMERGENCE OF THE RADICLE

 

 

 

 

   A STEM IS DIVIDED INTO TWO

   PARTS

 

   1.   HYPOCOTYL - PORTION BELOW

      THE COTYLEDONS

 

   2.   EPICOTYL - PORTION ABOVE

      THE COTYLEDONS

 

IF THE HYPOCOTYL ELONGATES FIRST, PULLING THE COTYLEDONS AND FIRST LEAVES THROUGH THE SOIL, THE GERMINATION IS SAID TO BE EPIGEAL GERMINATION

 

IF THE HYPOCOTYL DOESNíT ELONGATE AND STAYS BENEATH THE GROUND THE GERMINATION TYPE IS HYPOGEAL

 

NEW CELLS AND ORGANS ARISE FROM MERISTEMS

 

 

 

 

   1.   SHOOT APICAL MERISTEM

 

      a.   LOCATED AT THE APEX OF

         THE STEM

 

      b.   SURROUNDED BY LEAF

         PRIMORDIA

 

      c.   GIVES RISE TO ALL THE            OTHER CELLS AND TISSUES             IN THE PRIMARY SHOOT

 

         1.   STEMS

         2.   LEAVES

         3.   BRANCHES

         4.   FLOWERS

 

      d.   DIVIDED INTO TWO ZONES

 

         1.   OUTER TUNICA

            a.   GIVES RISE TO THE

               EPIDERMIS

 

 

.

         2.   CORPUS

            a.   GIVES RISE TO

               INTERNAL STEM AND

               LEAF TISSUES

 

      e.   THE STEM ELONGATES AND            FINAL HEIGHT IS                   DETERMINED BY THE EXTENT        OF INTERNODE ELONGATION.

 

         1.   THE INTERNODE IS THE               STEM    BETWEEN THE                  NODES

 

         2.   IF THE INTERNODES                   DONíT ELONGATE, THE               PLANT IS ROSETTE

 

            a.   NO ELONGATION IS                   OFTEN A RESULT OF                LOW GIBBERELLIC

               ACID (GA)                         PRODUCTION

 

      f.   LEAF PRIMORDIA ARISE ON             EITHER SIDE OF A                MERISTEM DUE TO

         INCREASED CELL DIVISION

 

      g.   LEAF ARRANGEMENT IS             SPECIES   SPECIFIC AND IS             CALLED PHYLLOTAXY

 

         1.   LEAF ARRANGEMENT MAY                BE:

 

            a.   OPPOSITE

 

            b.   ALTERNATE

 

            c.   WHORLED

 

ALL OF THE ABOVE ARE PARTS OF THE PRIMARY PLANT BODY

 

THE SECONDARY PLANT BODY IS A

RESULT OF A SECONDARY MERISTEM CALLED THE VASCULAR CAMBIUM

 

 

 

ROOT DEVELOPMENT

 

   THE ROOT APICAL MERISTEM IS

   LESS COMPLEX THAN THE SHOOT

   APICAL MERISTEM

 

      1.   DONíT PRODUCE BRANCH              ROOTS

 

      2.   COVERED BY A ROOT CAP

 

         a.   PROVIDE MECHANICAL

            PROTECTION

 

         b.   SECRETES MUCIGEL

 

            1.   LUBRICATES THE ROOT

               TIP AS IT MOVES

               THROUGH THE SOIL

 

      3.   HAS A QUIESCENT ZONE

 

         a.   A REGION OF SLOWLY

            DIVIDING CELLS

 

 

      4.   HAS A PERICYCLE

 

         a.   A RING OF                            MERISTEMATIC CELLS

            THAT GIVE RISE TO                   LATERAL ROOTS

 

FLOWER DEVELOPMENT

 

A STEM APICAL MERISTEM CHANGES TO A REPRODUCTIVE MERISTEM.  WE DONíT KNOW WHY

 

FLOWERING IS DIVIDED INTO THREE STAGES:

 

   1.   INDUCTION

 

   2.   EVOCATION

 

   3.   DEVELOPMENT

 

 

 

 

1.   INDUCTION REFERS TO THE EVENTS    THAT SIGNAL A PLANT TO    REORGANIZE A SHOOT APICAL    MERISTEM TO PRODUCE FLORAL    PARTS

 

2.   EVOCATION REFERS TO THE EVENTS

   FOLLOWING INDUCTION

 

   a.   INCREASE IN RESPIRATORY

      SUBSTRATES

   b.   INCREASE IN RESPIRATION           RATE

   c.   CHANGES IN RNA

   d.   CHANGES IN PROTEIN                   SYNTHESIS

 

3.   FLORAL DEVELOPMENT

 

   FLORAL PRIMORDIA DEVELOPE IN

   PLACE OF VEGETATIVE PRIMORDIA

 

   FLOWER PARTS REPLACE LEAVES