Transcript Soil N contents influenced by Insects

How do insect parameters
compare to those from plants?
, Yiyi Wong, Zuo Xue, Geoff Sinclair
• Components of insects
– Cuticle
– Chitin
• Amino Acids
• Amines, Amides, Alcohols, Ethers
• Review components of plants
• Results of FTIR, C:N ratio, and δ13C of
Grasshoppers
• Implications
Components of Insects
• Cuticle is the main
components of
insects
• Major molecular
component chitin
Among insects, grasshoppers have the highest total-nitrogen body
content but typically feed on food that is very low in nitrogen
• Cuticle
Chitin
• Polysaccharide and polymer
• Sometimes considered to be a spinoff of
cellulose, because the two are very molecularly
similar.
• Insect coats contain thick, stiff layers of chitin.
The areas around legs and face contain very
thin, pliable layers.
• Insects molt approximately once a year.
Structure of Chitin
Most of grasshoppers’ physiological and biochemical
processes require amino acids as building blocks
• Amino Acids(10 types)
Review of Plant Components
• Roots
– Carbohydrates
• Stems
– Cellulose
• Leaves
– Chlorophyll, Rubisco
– Misc. Carbohydrates, Proteins
Results - FTIR
• Fourier Transform Infrared Spectroscopy
(FTIR) is an analytical technique used to
identify organic and in some cases inorganic
materials.
• Measures the absorption of various infrared
light wavelengths by the material of interest.
These infrared absorption bands ID specific
molecular components and structures.
Expected Components of Spectrums
• Looked at the
chemical
components of chitin
and expected to see
the following:
–
–
–
–
Amines
Amides
Alcohols
Ethers
Expected Components of Spectrums
• Amines
– 1650-1580 bend
• Amides
– 1340-1020 stretch
• Alcohols
– 3600–3200s stretch
– 1260-1000s stretch
• Ethers
– 1760-1670s stretch
– 1260-1000s stretch
prp11 green grass
prp 8 vein
grasshopper
Absorbance
0.6
0.5
0.4
0.3
0.2
4000
3500
3000
2500
2000
Wave number
1500
1000
Results - Grasshopper C:N Ratios
• Expect the C:N ratios to reflect Chitin
• Tried to determine if there were
differences within the grasshopper via
body parts
– Did not any differences
High N and C contents in Grasshopper
compared to Soil and Plant samples
(averaged value)
N_Plant
N_Soil
N_Hopper
C_Plant
C_Soil
C_Hopper
1.91
0.40
11.87
43.43
10.22
51.44
Nitrogen Content(%)
Carbon Content(%)
14
60
12
50
10
40
8
30
6
20
4
2
10
0
0
N_plant
N_soil
N_hopper
C_plant
C_soil
C_hopper
Nitrogen Allocation Difference
Nitrogen%
N contents
14
12
10
8
6
4
2
0
N contents
Grasshopper Grasshopper Grasshopper Grasshopper
Full Body - Full Body - Full Body - Full Body Head
Leg
Body
Wing
Plant N contents influenced by
Grasshoppers
Research results about the N content on a certain of wheat (G.microcephala)
affected by the attack of grasshoppers.
Soil N contents influenced by
Insects
• 1. Insect herbivores can deposit significant quantities of
faecal material (frass) onto litter and soil.
• 2. Nutrients returned to soils in insect cadavers are
more easily decomposed than those in leaf litter and can
stimulate the decomposition of litter during defoliator
outbreaks.
• 3. Insect defoliation changes the nutrient content of
precipitation as it passes through plant canopies.
• 4. Herbivores can change the quantity and quality of leaf
litter that falls from plant canopies to the soil.
Soil N contents influenced by
Insects
• 5. Herbivore-mediated changes in plant community
composition not only influence litter quality, but may also
affect the utilization of soil nutrients by the new
community.
• 6. Herbivory may influence root exudates or interactions
between roots and their symbionts, both of which are
known to influence nutrient dynamics.
• 7. Herbivores can influence the structure of plant
canopies and the cover that they provide, with
concomitant changes in light availability, soil temperature
and moisture.
Results for δ13C Insect Diet
• On the whole, animals have similar δ13C to their food
source
– Body parts containing more protein are generally 13Cenriched
– Body parts containing more lipids are generally13Cdepleted
• Did not find many differences between grasshopper
body parts
–
–
–
–
Samples were cross-contaminated
Mixed Diet
Adult sample
Grasshoppers molt yearly
δ C13 with grasshopper parts
-19
-19.5
Grasshopper Full Body Head
δC13
-20
Grasshopper Full Body Leg
-20.5
Grasshopper Full Body Body
-21
Grasshopper Full Body Wing
-21.5
-22
1
Differences Between Plants and Insects
• Chitin vs Cellulose
– Cellulose contains a hydroxy group and chitin contains
acetamide.
• Plants have different C:N and δ13C values within the
anatomy
• Grasshopper samples did not show differences in C:N
values b/c most components consist of chitin
• Grasshopper samples did not show varying values of
δ13C although literature suggests that it is a possibility