Transcript 03. plants and environment factors

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An understanding of the ways individual
plants and their physiology are impacted by
different factors of the environment is an
essential component in the design and
management of cropping system
The ecological study of individual plant
response to the diverse factors of
environment (autecology or physiological
ecology) is a foundation of agroecological
understanding
1.
2.
3.
Photosynthesis
Carbon Partitioning
Transpiration
“Plants convert solar energy into chemical
energy stored in the chemical bonds of sugar
molecules”
this process is IMPORTANT for
plant growth and survival
Remember what plants need…
 Photosynthesis

light reactions
 light
 sun
 H 2O

Calvin cycle
 CO2
 air
 ground
•Fotosintesis
•Proses dimana organisme
yang memiliki kloroplas
mengubah energi cahaya
matahari menjadi energi kimia
•Melibatkan 2 lintasan
metabolik
•Reaksi terang: mengubah
energi matahari menjadi
energi seluler
•Siklus Calvin: reduksi CO2
menjadi CH2O
Simple equation :
6CO2 + 12H20 + light energy
C6H12O6 + 6O2 + 6H2O
Light energy
ECOSYSTEM
Photosynthesis
in chloroplasts
CO2 + H2O
Cellular respiration
in mitochondria
ATP
powers most cellular work
Heat
energy
Organic
molecules
+ O2
Energi mengalir ke
dalam suatu
ekosistem sebagai
cahaya matahari dan
meninggalkannya
dalam bentuk panas
Types of Photosynthesis
•
C3 photosynthesis
–
Most plants
•
C4 photosynthesis
–
A variety of plants, especially our summer
annuals and many of our grasses
•
CAM photosynthesis
–
Cacti, agaves, bromeliads, and others
C3 plants
 The
first stable compound formed in dark
reactions (Calvin cycle) is 3-carbon compound
 A problem
with C3, photosynthesis is always
accompanied by photorespiration which
consumes and releases CO2 in the presence of
light
 it
wastes carbon fixed by photosynthesis - up to
50% of carbon fixed in photosynthesis may be
used in photorespiration
C4 plants
A better way to capture CO2
• 1st step before Calvin cycle,
fix carbon with enzyme
PEP carboxylase
 store as 4C compound
• adaptation to hot, dry climates
 have to close stomates a lot
 different leaf anatomy
• sugar cane, corn,
other grasses…
sugar cane
corn
 Photorespiration
is nearly absent in C4 plants - so
greatly increases their efficiency - this is because a
high CO2: low O2 concentration limits
photorespiration
 Thus
net photosynthetic rates are higher for C4
plants (corn, sorghum, sugarcane) than in C3
relatives (wheat, rice, rye, oats)
CAM (Crassulacean Acid Metabolism) plants

separate carbon fixation from Calvin cycle by time
 close stomates during day
 open stomates during night

at night, open stomates & fix
carbon in “storage” compounds
 organic acids: malic acid, isocitric acid

in day, close stomates & release CO2 from “storage”
compounds to Calvin cycle
 increases concentration of CO2 in cells

succulents, pineapple, cactuses, agaves,
bromeliads
CAM plants
how plant distributes the carbon
compounds derived from photosynthesis
and allocates them to different
physiological processes and plant parts
Transpiration
the continual flow of water from the soil,
into the roots, up the stem to the leaves, and
out of the leaves through the stomata
Water moving between soil and plants
flows down a water potential gradient
A
Plant’s Place in the Environment
- Each species occupies a particular
place in the ecosystem, known as the
habitat
- within its habitat, the species carries out
a particular ecological role or function,
known as the ecological niche of that
species
 Responses
to Factors of the Environment
Setiap fase perkembangan tanaman
melibatkan respon perubahan secara fisiologis.
Sebagian besar respon tanaman berkaitan
langsung dengan kondisi lingkungan
- Triggered Responses
- Dependent Responses
- Independent Responses
 Triggered
Responses
respon tanaman yang dipacu oleh adanya eksternal
stimulus tertentu
 Dependent
Responses
respon tanaman yang tergantung pada keberadaan
kondisi lingkungan eksternal tertentu secara terus
menerus
 Independent
Responses
respon tanaman yang ditentukan oleh kondisi
fisiologis tanaman; mis: tanaman jagung akan berbunga
karena fase tertentu dari pertumbuhan dan perkembangan sudah
tercapai.
 Limits
and Tolerances
Each environmental factor has both
minimum and maximum levels, tolerance
limits, beyond which a particular species
cannot survive
1.
2.
3.
Buat tulisan lengkap tentang tipe
fotosintesis
Batasan cahaya matahari yang dapat
dimanfaatkan tanaman untuk
fotosintesis
Bagaimana adaptasi tanaman terhadap
kelebihan dan kekurangan cahaya?