Sugarcane

Egypt


Botanical Characteristics

The main parts of the sugarcane plant are the

         1 - The stalk

         2 - The leaf

         3 - and The root system

Source of Information

 

             

 

1-The Stalk

  • The stalk consists of segments called joints.
  • Each joint is made up of a node and an internode.
  • The node is where the leaf attaches to the stalk and where the buds and root primordia are found.
  • A leaf scar can be found at the node when the leaf drops off the plant.
  • The length and diameter of the joints vary widely with different varieties and growing conditions.
  • The joints at the base are short and internodal length gradually increases.

                                        

  • The buds, located in the root band of the node, are embryonic shoots consisting of a miniature stalk with small leaves.
  • The outer small leaves are in the form of scales.
  • The outermost bud scale has the form of a hood.
  • Normally, one bud is present on each node and they alternate between one side of the stalk to the other.
  • Variations in size, shape and other characteristics of the bud provides a means of distinguishing between varieties.
  • The root band also contains loosely defined rows of root primordia.
  • Each primordium exhibits a dark center, which is a root cap, and a light colored "halo."
  • When seed-cane is planted, each bud may form a primary shoot.
  • From this shoot, secondary shoots called "tillers" may form from the underground buds on the primary shoot.
  • In turn, additional tillers may form from the underground secondary shoot buds.
  • The colors of the stalk seen at the internodes depend on the cane variety and environmental conditions.
  • For example, exposure of the internodes to the sun may result in a complete change of color.
  • The same variety grown in different climates may exhibit different colors. 

                -All colors of the stalk derive from two basic pigments: the red color of anthocyanin and the green of chlorophyll.

    -The ratio of the concentration of these two pigments produce colors from green to  purple-red to red to almost black.

    - Yellow stalks indicate a relative lack of these pigments. The surface of the internode, with the exception of the growth ring, is more or less covered by wax.

  • The amount of wax is variety dependent.
  • Where the internode is exposed to the elements, a black mold usually develops on the waxy surface.
  • The top of the stalk is relatively low in sucrose and therefore is of little value to the mill early in the harvest season.
  • However, the top 1/3 contains many buds and a good supply of nutrients which makes it valuable as seed cane for planting.
  • A cross section of an internode shows, from the outside to the center, the following tissues: epidermis, cortex or rind, and ground tissue with embedded vascular bundles. The epidermis is a single superficial layer of cells that exhibit different patterns which are variety dependent.
  • Generally, the patterns are formed by two cell types, the so-called long cells and short cells that alternate with one another.
  • The cortex or rind consists of several layers of cells just inside the epidermis.
  • The cells of the rind are thick-walled and lignified.
  • These cells help strengthen the stalk.
  • More toward the center, the ground tissue contains the vascular bundles with the xylem and phloem.
  • Xylem tissue conducts water and its dissolved minerals upward from the roots, and phloem conductive tissue transports plant- manufactured nutrients and products, for the most part, downward toward the roots.
  • The vascular bundles are much smaller and more prevalent toward the periphery of the stalk.
  • Two types of cracks are sometimes found on the surface of the stalk; harmless, small corky cracks which are restricted to the epidermis, and growth cracks which may be deep and run the whole length of the internode.
  • Growth cracks are harmful since they allow increased water loss and expose the stalk to disease organisms and insects.
  • Growth cracks are dependent on variety and growing conditions.

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2-The Leaf

  • The leaf of the sugarcane plant is divided into two parts:

               a-sheath

               b- and blade, separated by a blade joint.

  • The sheath, as its name implies, completely sheaths the stalk, extending over at least one complete internode.
  • The leaves are usually attached alternately to the nodes, thus forming two ranks on opposite sides.
  • The mature sugarcane plant has an average total upper leaf surface of about 0.5 square meter and the number of green leaves per stalk is around ten, depending on variety and growing conditions.

                                            

  • A cross-section through the leaf blade would show three principal tissues:
  • epidermis,
  • mesophyll,
  • and veins or fibrovascular bundles.
  • The epidermal cells protect the underlying tissues from injury and drying.
  • The epidermis contains stomata for controlling the exchange of gases.
  • The mesophyll, or middle leaf tissue, contains the cells that perform most of the photosynthesis.
  • The fibrovascular bundles contain the xylem and phloem elements which conduct water and nutrients to and from the leaves.
  • In addition to the above, there can be found other fibrous tissue for aiding in shaping and mechanically strengthening the leaves.
  • The blade joint is where two wedge-shaped areas called "dewlaps" are found .
  • The color, size, and shape of the dewlaps on a mature plant are more or less characteristic of a variety.
  • The "top visible dewlap" leaf is a diagnostic tissue that is frequently used in nutritional studies.
  • The leaf sheath is similar in structure and function to the leaf blade.
  • It is slightly simpler, however, in that it lacks some of the more specialized cells of the leaf blade.
  • The ligule is a membranous appendage inside of the sheath which separates the sheath from the leaf blade.
  • It is a slightly asymmetric organ whose color, size, and shape are age and variety dependent.
  • The auricles, as their name implies, are ear-shaped appendages located at the upper part of the sheath margin.
  • Not all sheath margins have auricles.
  • Leaf pubescence, or the covering of the various leaf parts with short hairs, is also variety and age dependent.
  • Pubescence is not found on the leaf blade of commercial varieties, but does exist in sugarcane germplasm.
  • Sheath pubescence can be used to identify plants.

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3-The Root System

  • The function of the root system is twofold:

     -first, it enables the intake of water and nutrients from the soil;

      -and second, it serves to anchor the plant.

  • Two kinds of roots will develop from a planted seed piece.
  • The set roots, which arise from the root band, are thin and highly branched; the shoot roots, originating from the lower root bands of the shoots, are thick, fleshy and less branched .

                                 

  • Before shoots form, the germinating seed piece must depend entirely on the set roots for water and nutrients.
  • The set roots, however, are only temporary and their function will eventually be taken over by the shoot roots as they develop.
  • The life of the shoot root is also limited.
  • Each new tiller (shoot) will develop its own roots that eventually take over the function of the original shoot roots.
  • This rejuvenation, governed by the periodicity of tillering, is important because it allows the plant to adjust to changing environmental conditions.
  • A longitudinal section of a root tip consists mainly of four parts:

1.       the root cap,

2.      the growing point,

3.      the region of elongation,

4.      and the region of root hairs.

1)      The root cap protects the tender tissues of the growing point as the root pushes through the soil.

2)      The growing point consists mainly of an apical meristem, where cell division takes place.

3)      In the region of elongation, the cells increase in size and diameter until they reach their ultimate size.

4)      The region of root hairs is characterized by epidermal cells forming outgrowths (hairs) which dramatically increase the root absorbing surface.

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This information is collected from

http://edis.ifas.ufl.edu/SC034

 

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