Physiology of Roots in Sugarcane

2. Represented to:
Dr. Hassan Munir Bajwa
Represented by:
Muhammad Shahzad Alam
Ag No.:
2018-ag-17
Subject:
C.phy-714
Physiology of Roots in Sugarcane

3. Physiology of Roots in Sugarcane

5. Growth and development of the sugarcane root system
The first roots formed are sett roots, which emerge from a band of root
primordia above the leaf scar on the nodes of the sett.
These roots are thin and branched.
The main function of these roots is to provide water and nutrient to the
young developing shoots.
Sett roots can emerge within 24 h of planting although differences in the
time required for root emergence occur among varieties.

6. Conti…
Sett roots are fine and highly branched roots which sustain the
growing plant in the first weeks after germination.
The life span of theses roots is relatively short (2-3 months).
There function is taken over by shoots roots.

7. Conti…
The root band is a small section of the stalk just above the node.
 This is generally somewhat different in color and on it occur a great
many small dots usually in rows.
 These dots are thin places in the rind tissue and are directly over the root
primordia.
 Under the right moisture conditions, a root develops from each of these.
All the roots which are produced by the cane plant come from the root
band area.

8. Conti…
The portion of the stalk underground, which is structurally no different
from the portion above ground, is often called the rootstalk.
In Louisiana, these portions after harvest are called stubbles.
 During the growing season, the buds on the rootstalks develop into
suckers and the roots which are necessary for the growth of the plants
develop from the root bands on the internodes.

9. Conti…
The roots of the sugar cane plant are fibrous in nature.
The main roots which develop from the root band on the growing stalk
are usually called the primary roots.
 As the roots grow, they branch repeatedly and finally permeate the soil
in every direction.
 The branches are usually called secondary and tertiary roots.
A root when first formed is nearly white in color and is covered with
many small root hairs.

10. Conti…
As the root extends further out in the soil, the older portion near the stalk
becomes dark in color and the root hairs disappear.
Absorption of water and mineral salts takes place to a very large extent in
the white portion near the tip.
 A cross section of the white portion shows that there are two main parts
of the root, the stele and the cortex.
 The stele located in the center of the root is more or less circular in cross
section and contains a number of large openings which are the open ducts
through which the soil solution absorbed by the roots is carried back to
the stalk.

11. Conti…
The cortex is the rather thick area surrounding the stele.
 The root hairs extend outward from the outer layer of cells, the
epidermis.
The soil solution is taken up by the root hairs and epidermis and is
then carried through the cortex cells to the ducts in the central stele.
If a section is made through the older dark colored portion of the
root, it will be seen that the cortex cells are dead and are left in the
form of shreds connecting the epidermis to the stele.
The cortex has become merely a spongy dead layer surrounding the
living, functioning stele.

12. Conti…
It seems that as soon as the young portion of the root grows out, the
old portion ceases to function as an absorbing organ and the cortex
cells, being of no further use, die.

13. Conti…
Shoot roots are a second type of root which emerge from the base of the
new shoot 5–7 days after planting.
The shoot roots are thicker and fleshier than sett roots and develop into
the main root system of plant.
Sett roots continue to grow for a period of 6–15 days after planting.
Mostly senescing and disappearing by 60–90 days.
 By the age of 3 months, sett roots comprise less than 2% of root dry
mass.

14. Conti…
 Roots absorb the water and mineral salts which are necessary if
growth activities are to continue.
Roots also support the plant and act as organs of storage, storing up
materials which can later be used by the plant.
The activities of roots are influenced to a very great extent by the
soil conditions around them.

15. Shoot roots
Shoot roots differentiated into three functional types as the
sugarcane plant developed.
i. Superficial roots
ii. Buttress roots
iii.Rope roots

17. Superficial roots
Roots emerging from higher nodes were thinner and highly branched,
extending laterally to form a dense network of ‘superficial roots’
responsible for uptake of water and nutrients from surface soil layers.
These roots are thin and branched.
They grow away from the stool and the rootlets on the branches bear
numerous root hairs.
They provide the plant with most of its water and mineral
requirements expect under dry condition when plant will depend upon
the deeper roots.

18. Buttress roots
The first roots to emerge from the base of the young shoot were thickened
with little branching and grew outwards and downwards into the sub-soil
to a depth of up to approximately 1.5 m, thus forming ‘buttress roots’
adapted to anchorage of the plant.
The buttress roots are thicker than the superficial ones and grow deeper
down at an angle into the soil profile.
The main function is anchorage although they may absorb water as well.

19. Rope roots
The third class of roots were ‘rope roots’, formed from
agglomerations of vertical roots.
They grows more or less vertically down through the soil profile
and forms strands.
These may go to the great depth.
They may provide the plant with some water under drought
conditions.

21. Root growth and distribution
Sett roots initially have an elongation rate of a few mm reaching within a
few days of germination under favourable conditions.
 Shoot roots grow more rapidly, with maximum rates of elongation of up
to 80 mm though only for short periods.
Most root biomass for sugarcane is found close to the surface and then
declines approximately exponentially with depth.

22. Conti…
Typically, approximately 50% of root biomass occurs in the top 20 cm of
soil and 85% in the top 60 cm.
Sugarcane may therefore have a some what deeper root distribution than
is typical for crops, likely reflecting the length of the crop growth cycle
and the longevity of the root system through multiple ratoons.
The maximum depth of sugarcane roots, however, has not been widely
observed.
The maximum depth of root sampling is typically restricted to 1.5 or 2
m, with small amounts of sugarcane roots routinely found at such depths.

23. Root system plasticity and function
Root growth responds strongly to the soil environment, creating
plasticity in the form and size of the root system.
High soil strength is a cause of reduced root growth.
 Sugarcane roots are thickened under such conditions with reduced
branching, in addition to slower growth.
In a poorly structured heavy clay soil reduced root system size
relative to sandy or loam soils was associated with high soil
strength and waterlogging.

24. Conti…
Uptake of water and nutrients from the soil volume occupied by roots is
facilitated by root branching.
In many species root system plasticity resulting from prolific root
branching in nutrient-rich patches may increase exploitation of soil
resources, particularly for non-mobile nutrients such as phosphorus
noted considerable variation among cultivars in their capacity for root
branching.
Highly branched superficial roots improve drought-tolerance in
cultivars exhibiting low root mass, implying that intensity of branching
can partly compensate for restrictions on the volume of soil occupied
by the root system.

25. Conti…
Root senescence causes root branching to decline as the sugarcane crop
matures, which he interpreted as the cause of lower uptake of N and
water by older crops.
The size and distribution of the root system is strongly affected by the
distribution and availability of soil water, causing differences in the
capacity of crops to exploit deeper soil resources.
Deeper rooting reduces the vulnerability of crops to soil water deficits
by providing increased capacity for uptake of deep reserves of soil
water.

26. References
 Smith, D. M., Inman-Bamber, N. G., & Thorburn, P. J. (2005). Growth and function of the
sugarcane root system. Field Crops Research, 92(2-3), 169-183.
 Ryker, T. C. (1931). Studies on sugar cane roots.
 Miller, J. D., Gilbert, R. A., & Odero, D. C. (2009). Sugarcane botany: A brief view. University of
Flórida, IFAS Extension.