Upload
joshua-tiglao
View
225
Download
0
Embed Size (px)
Citation preview
8/3/2019 Vegetative Structure and Function
1/31
8/3/2019 Vegetative Structure and Function
2/31
ROOTS Origin of the Root
Hypocotyl portion of theembryo axis located below thecotyledonary node that giverise at its tip to the radicle
Radicle - lowermost porion of
the embryonic axis of a seed.Responsible for theproduction of the primaryroot
Primary Root from the maintrunk or from the hypocotyl
Secondary roots arise fromthe primary root
Adventitious roots fromstems, leaves and other partsof plants
Developed from structures otherthan the hypocotyl or primary
root.
8/3/2019 Vegetative Structure and Function
3/31
8/3/2019 Vegetative Structure and Function
4/31
Types of Root System
Taproot System
Characteristic of dicots
Primary roots continue to growand send out lateral smaller roots
Fibrous or Diffuse Root System Characteristic of monocots
Primary root stops growing and
numerous adventitious rootsgrow and develop from the baseof the stem and take the place of
the primary root.
8/3/2019 Vegetative Structure and Function
5/31
Functions of the Roots
Anchorage-locate
Absorption- extracts
Storage- store and hoard
Conduction-transport
8/3/2019 Vegetative Structure and Function
6/31
Structure of Roots
Root tip
Root cap
Composed of elongatedcolumella cells that later
develop into peripheral cells
meristem
Senses light and pressure
exerted by soil particles
Secretes slimy substancemucigel, that aid in
protection, lubrication, water
and nutrient absorption
8/3/2019 Vegetative Structure and Function
7/31
8/3/2019 Vegetative Structure and Function
8/31
Quiscent center Located just behind the root cap
Composed of 500-1000 inactivecells arrested in G1 phase
Divides only once in 15-20 days Unaffected by radiation and
other extreme environmental
con t ons Functions as reservoir to
replace damaged cells ofmeristem
Reorganizes patterns of primarygrowth in roots
8/3/2019 Vegetative Structure and Function
9/31
Subapical region Zone of
cellulardivision
Zone of
cellular
elongation
Zone ofcellular
maturation
8/3/2019 Vegetative Structure and Function
10/31
Zone of cellular division
Dome-shaped apical meristem
surrounding the quiscent center
Located 0.5-1.5 mm behind the root
itp
ompose o ense y un eren a ecytoplasmic cells
Divides every 12-36 hours
Produces almost 20,000 new cells perday
8/3/2019 Vegetative Structure and Function
11/31
Zone of cellular elongation
4-15 mm behind the root tip
Long vacuolated cells
Process of differentiation starts
8/3/2019 Vegetative Structure and Function
12/31
Zone of cellular maturation
Process of differentiation
complted
10-50 mm behind root tip
on-e ongate , mature ce s Presence of many ephemeral
root hairs
8/3/2019 Vegetative Structure and Function
13/31
Mature region
Epidermis
Cortex
Stele
8/3/2019 Vegetative Structure and Function
14/31
Epidermis
Covers root except root cap
Usually one cell thick; lacks stomata
Lacks a cuticle or have a thin layer cuticle
8/3/2019 Vegetative Structure and Function
15/31
Cortex
Interior to epidermis
Occupies largest cross-sectional area of root
Consists of 3 concentriclayers
ypo erm s protect roots Parenchyma tissue stores
energy reserves
Endodermis lined withCasparian strips, whichdiverts water and dissolvedminerals into cytoplasm of
endodermal cells
8/3/2019 Vegetative Structure and Function
16/31
Stele Includes all tissues inside
the cortex
Pericycle produces branchroot
Vascular tissue x lem and
phloem form in laternatingstrands interior to thepericycle
Most dicots have solid coreof xylem
Most monocots have
parenchymatous pith
8/3/2019 Vegetative Structure and Function
17/31
STEMS
Origin of Stems
Epicotyl
Portion of the embryo axis in the seed
Short cylindrical structure bearing a small mass meristematic
tissue and frequently a pair or more of tiny leaves at its tip
Immature shoot that later becomes the stem
8/3/2019 Vegetative Structure and Function
18/31
Kinds of Stem As to location
Aerial or epiterranean - above surface
Underground or subterranean-beneath soil
Rhizome horizontal direction bearsmost of the feature of t ical stem
e.g. ginger Corn arise from base of an aerial
shoot covered with dry leaves e.g.taro (gabi)
Bulb stem of bulb is in the form or
reduced, flattened disc e.g onion
8/3/2019 Vegetative Structure and Function
19/31
Functions of Stem Store materials
parenchymal cells
Support leaves- turgor
pressure
Transport water andsolutes betwwen roots
and leaves vascular
system
Produce carbohydrates -
chlorophyll
8/3/2019 Vegetative Structure and Function
20/31
External Structure of Stem Node leaves and buds arise
Internode- between 2successive nodes
Lenticel- tiny raised pores on
for gas exchange
Scar- remnant mark from leaf,bundle, bud, fruit, flower,
twig Bud immature shoot,
largely meristematic
8/3/2019 Vegetative Structure and Function
21/31
Internal Structure of
Stem
Epidermal tissue
Transparent cells
surrounding stem
ne ce t c t at o tenbears trichomes
in dicot trees, modified into
bark as plant grows older
8/3/2019 Vegetative Structure and Function
22/31
Vascular tissue
Embedded in the ground tissue
Composed of xylem and phloem occurred in
vascular bundles Phloem for the transport of food from the leaves down
to the roots and other parts of the plant, and xylem for
the transport of water from the roots up to the leaves.
8/3/2019 Vegetative Structure and Function
23/31
8/3/2019 Vegetative Structure and Function
24/31
Vascular bundles are arranged differently in differentrou s of lants
Monocots have vascular bundles embeddedthroughout the ground tissue, where phloemoriented outward and xylem inward
Most dicots have a single ring of vascular bundlesembedded in the ground tissue
Many non-flowering plants and few dicots haveconcentric cylinders of xylem and phloem
8/3/2019 Vegetative Structure and Function
25/31
Ground tissue In dicots, the parenchymatous ground tissue is
composed of cortex and pith
Because monocots have vascular bundles
throughout their ground tissue, their stems do
not ave cortex or pit
8/3/2019 Vegetative Structure and Function
26/31
LEAVES
Origin of Leaves
Leaf primordia
Outgrowths of the apicalmeristem in terminal and
lateral buds
its position in the bud
determines the relative
position of leaves on the
stem the first pair of leaves are
produced during the
development of the seedling
8/3/2019 Vegetative Structure and Function
27/31
Leaf Morphology
Petiole stalk of the leaf that
connects the leaf blade to thenode of the stem
Blade broad, flat,photosynthetic portion of a
leaf divided into: Veins vascular tissues within
a leaf located on both sides ofe m r
Midrib narrow, thickenedstructure which is acontinuation of the petiole andextends through the center of
the blade to the opposite end;the major vein in a leaf thatdivides the blade into twohalves
8/3/2019 Vegetative Structure and Function
28/31
Stipule small paired
leaf-like structures atthe base of the leaf
stalk found on cetrtain
plants
Leaf sheath the base
of the leaf blade thatcompletely encircles
the portion of the
internodal segment ofthe stem, present
among grasses
8/3/2019 Vegetative Structure and Function
29/31
Leaf Anatomy
Upper and lower Epidermis Transparent, not pigmented
Coated with waxy material, cuticle
Cells are modified in the form of hairs and glandular cells
Presence of chloroplast-containing guard cells (small
opening is called stoma)
8/3/2019 Vegetative Structure and Function
30/31
Mesophyll
oca e e ween ep erma ayers
Made up of parenchymatous, photosynthetic tissues
Consists of 2 distinct types:
Palisade layer- vertically elongated comunar cells arrangedbelow the upper epidermis
Spongy layer irregular parenchymatous cells with manyintercellular spaces (called stomata chambers) arranged
above the lower epidermis
8/3/2019 Vegetative Structure and Function
31/31
Vascular bundles
Consists of primary xylem and primary phloem surroundedby a bundle sheath
Also conatin sclerenchymatous fibers or collenchyma cells
No vascular cambium Xylem composed of vessel elements located toward the
upper epidermis
Phloem- composed of sieve tubes, members and
companion cells located toward the lower epidermis