Lecture 5: Starchy Staple, root design and function Flashcards
What are the characteristics of the root?
lower part of axis subterranean lack of chlorophyll indeterminate apical meristem highly branched
How many axes and laterals does winter rye have?
13 million (about 1 million per day)
What is the total length on average occupied by the roots of winter rye?
greater than 500 km
What is the average surface area covered by the roots of winter rye?
greater than 200 m^2
What are the functions of roots?
anchorage absorption (water and minerals) storage (has parenchyma) rhizosphere synthesis ( roots can make particular compounds)
What does it mean by rhizosphere?
the bacteria and fungi extend the plants’ reach into the soil
Describe dicot roots
branch acropetally
the tap root penetrate deeper than monocots
due to acropetal structure; binds less tightly to soil
suberized (make wood)
secondary growth ( the formation of vascular cambium and cork cambium)
Describe monocot roots
wide branch angle (enables it to bind more tightly to soil)
sclerenchyma cells conger rigidity
shallow roots
Describe the penetration process of a dicot?
radicle to
tap root to
lateral roots
Describe the penetration of monocot roots
tap root to
fibrous adventitious
Define contractile roots
eg. carrots, hyacinth, sugar beet
- contracts up to 70%
- swells outwards
- draws apex down the soil
- contracted part may be a storage organ
What is the benefit of contracting these organs?
So that it won’t get eaten; keep the energy
true or false; soil structure affects growth
true
How does compact soil affect root growth?
resistance to root growth
How does lots of water in the soil affect root growth?
slows down root growth
How does less water in the soil affect root growth?
speeds up root growth; extensive branching
Why does less water speed up root growth?
because there is less amount of nutrients available
What is the flood response of roots?
formation of aerenchyma
What are hard pans?
iron rich soils
rigid pore structure
roots only grow in cracks
What happens when a root meets a pore smaller than itself (in hard pan soil)
the root forces the crack to open
How does the root force the small pore to open?
diameter of the root increases
tissue distortion
small extension zone
many root hairs grow in the zone of maturation thus increasing anchorage for pushing
What do you call roots that extract O2 from the atmosphere?
pneumatophores (mangroves)
What is the purpose of pneumatophores?
so that the starch (energy) stored in the roots can be released via respiration
What are epiphytes
- don’t grow on soil
- can absorb atmospheric moisture and nutrients via VELAMEN
What are flower pot plants characteristics
- leaf forms FLATTENED succulent structures (pot)
this collects - debris and rainwater
What is the purpose of ants living in flower pot plants?
ants deposit nitrogen
What is the purpose of adventitious roots of flower pot plants?
adventitious roots from node above grows down into ‘pot’ to absorb water and minerals
What are examples of root crops?
carrots
sugar beet
kumara
cassave
Where were carrots first domesticated?
Afghanistan
What was the color of the first domesticated carrot?
purple
How did the orange strain of carrot species come about?
16th century pale yellow variety was cultivated in Europe
Who cultivated the orange species?
Dutch breeders
What is the advantage of the orange colored carrots to its consumers
had more carbohydrate content
- has beta carotene which breaks down to vitamin A
- Vitamin A is a precursor for retinol
- retinol is light absorbing pigment in rod cells in the eye
Are carrots biennial or perennial?
biennial
What happens during these 2 years of carrot growth
1st year: stores reserves in swollen taproot
2nd year: reserves used to form flowers (release seeds)
Why does the storage tap root shrink during the second year of growth?
This is because energy is being used to produce leaves and flowers
How much % of parenchyma in cortex (starch and sucrose) are carrots composed of (dry weight)
20% sucrose
6% starch
Where did kumara originate?
South America
Where were Kumara first domesticated?
Peru
Who introduced Kumara to Europe and when?
Columbus (1492)
Where is the most Kumara grown nowadays?
China
Where is kumara an important staple food?
warm temperate countries
livestock feed in tropics
How much in % does the parenchyma of kumara contain (starch and succrose and protein)
30% starch + sugars
2% protein
How is kumara likely to be propagated nowadays?
from cuttings
true or false; 40% of the table sugar in the world today is from sugar beet?
true
Where is sugar beet native to?
the Mediterranean
How has selective breeding increased the sucrose content of sugar beet?
from 2% to 20%
What in its structure does sugar beet have a lot of ?
cambia
What does supernumerary cambia mean?
phloem
cambia
xylem
Where did cassava originate?
South America
- domesticated more than 3000 years
How much weight of the cassava in % is in the central pith of root
35%
How many people consider cassava as their staple food
800 million people; including 250 million in the sub- Saharan desert
how much in % is the calorie intake of cassava in Africa?
37%
true of false; cassava grows well in relatively dry regions?
true
How many years can cassava be stored?
3 years
true or false; cassava produces more starch per hectare under relatively dry conditions than any other known crop
true
Why is cassava poisonous if it wasn’t boiled?
contains cyanogenic compounds
cyanide is released when cells rupture
thus roots must be boiled or soaked & dried
How much is the estimated population growth of humans in the year 2050
9 billion
How many people in the world are under nourished?
1/7 of the world population
1.02 billion
What are the staple crops?
cassava, sweet potato, sugar beet, yams (rice, potato, maize, wheat, soybeans)
What is BioCassava plus
research
- international integrated team of scientists
- reduce malnutrition through improved cassava
- provide complete and balanced nutrition
- readily marketable higher yielding food crop
- aim for field testing in two african nations in 2010
- greater than 12.1 million dollars grant by Bill and Melinda Gates foundation
What are the aims of BioCassavaPlus
- increase the content of zinc and iron content in cassava tubers
- increase protein content of cassava
- increase vitamin A and E content of cassava tubers
- decrease cyanogen content
- delay post harvest deterioration of cassava tubers
- develop virus resistant cassava varieties