Sugarcane

Morphology

Morphology and Growth

  • Sugarcane is a tropical plant belonging to the family Gramineae, class monocotyledones and order glumaceae. Modern day sugarcane cultivars are complex hybrids evolved from various species. It is known by the scientific name Saccharum officinarum L.

Cane Morphology

  • Sugarcane is a giant grass of 12 month duration. It grows for 18 months in certain parts of the country and is known as adsali cane. In Hawaiian islands, it is grown for 24 months and it is a perennial grass.

Stem

  • Stem is also known as ‘stalk’ or "millable cane". It develops from the bud of another stem piece planted for vegetative propagation.
  • The stem pieces used for planting are known as `setts’ which contain one or several buds.
  • The bud sprouts under favourable conditions and gives rise to a primary stalk from which a secondary stalk is produced which in turn gives rise to a tertiary stalk, thus inducing tillering process. These stalks are differentiated into nodes and internodes.
  • The node is the base of the leaf. The internodes vary in shape, length and thickness depending upon the variety and growth conditions.
  • The various internode shapes are: Cylindrical, tumescent, bobbin shaped, conoidal, obconoidal and curved.
  • The buds are present in a longitudinal groove. On the tip of the bud a germination pore is present through which the sprouting shoot emerges. Under favourable conditions the buds germinate and thus ensure usual vegetative propagation.
  • The sugarcane stem is solid unlike most grasses which have hollow stems. Inside the rind tissue, the delicate parenchyma are present which contain the sucrose rich vacuoles.
  • The stem is generally coated with wax which is specific to each variety and growing conditions.
  • Usually, the stem is thicker towards base and tapers towards the top. The stem colour also varies with varieties.

Root

  • Sugarcane forms adventitious roots which sprout from the root bands of the setts. In most sugarcane growing soils, the bulk of the roots (about 90%) lies in the top 50 cm layer.

The leaf

  • The leaves sprout from the nodes and in the form of sheaths, at first envelop the stem. At the top of the cane and in the case of very young canes, they overlap thus providing effective protection to the growing point. As they grow older, the sheaths open up slightly.
  • The leaf sheath is at an angle to the cane. At the junction of the leaf sheath and blade is a thin membrane, called ligule, which envelopes the stem.
  • The leaf reaches a length of around 2m and width of 2 to 7 cm depending upon the variety. The leaf terminates in a pointed tip. The main vein runs centrally and serves to carry water and food.

Inflorescence

  • Sugarcane flower or inflorescence is also known as an "arrow". Therefore flowering is also known as "arrowing". It does not flower everywhere since it requires specific climate conditions.
  • Flowering is important for crossing and producing hybrid varieties. However, it is undesirable in commercial cultivation as it stops further growth and thus yield.

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Growth stages of Sugarcane

  • It is a C4 plant. It possesses C4 photosynthetic pathway. Therefore sugarcane is considered as one of the most efficient converter of solar energy, thus having potential to produce huge amount of biomass.
  • Sugarcane has essentially four growth phases, though it is difficult to recognise distinct duration of each. The growth phases are germination, tillering , grand growth and maturity and ripening.

Germination

  • The germination phase is from planting to the completion of germination of buds, Under controlled conditions, the germination occurs within a week to 10 days. But under field condition, the germination phase usually lasts for about 30-35 days. In sugarcane, germination denotes activation and subsequent sprouting of the vegetative bud.
  • Optimum temperature for sprouting is around 28-300 C. Warm, moist soil ensures rapid germination. About 60 percent germination can be considered safe for raising a satisfactory crop.

Tillering

  • Tillering starts from around 45 days and may last upto 120 days of the crop. Tillering provides the crop with appropriate number of stalks required for a good yield.
  • Light is the most important external factor influencing tillering. Adequate light reaching the base of the sugarcane plant during the tillering periods is of paramount importance.
  • Around 30 degree C temperature is considered optimum for tillering.
  • Usually early formed tillers give rise to thicker and heavier stalks. Late formed tillers either die or remain short or immature. Maximum tiller population reaches around 90-120 days of the crop.
  • Cultivation practices such as spacing, time of manuring, availability of water and weed control influence tillering. Though 6-8 tillers are produced from a bud, ultimately only 1.5 to 2 tillers per bud remain to form canes.

Grand growth

  • Out of the tillers produced, only about 40-50 percent survive to form millable canes by around 120-150 days. Then onwards, the stalks grow rapidly almost at the rate of 4-5 internodes per month under favourable conditions.
  • The cane elongation is facilitated by availability of adequate water, fertilizers and warm and sunny climatic conditions.
  • The grand growth phase lasts upto around 270 days in a 12 month variety. This is the most important phase of the crop wherein the actual cane formation and elongation and thus yield build up takes place. A temperature around 300 C with a humidity of around 80 percent is most conducive for good growth.

Maturation and ripening

  • Maturation and ripening phase or sucrose synthesis and accumulation phase lasts for about 3 months. The period between 270 to 360 days may be considered as maturity and ripening phase. During this phase rapid accumulation of sugar takes place and vegetative growth is reduced. As ripening advances, simple sugars (mono sacchardies viz., fructose, glucose) are converted into cane sugar (sucrose, a disaccharide).
  • Cane ripening proceeds from bottom to the top and hence bottom portion contains more sugars than the top portions. Ample sunshine, clear skies, cool nights and warm days and dry weather are highly conducive for ripening.

Composition of Sugarcane

Fibre 14 – 17 %
Water 63 – 75%
Total solids of the juice 17 – 22%
Reducing sugars 0.1 - 1.0%
Soluble impurities 1.5 – 2.5%
Saccharose (Pol) (Sucrose) 12 –20%

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