Introduction

• The potato is botanically known as Solanum Tuberosum L., and is a member of the Salamanca or nightshade family of plants.
• In the discussion of the Solanum, it is one of the largest genera in the vegetable kingdom, about 900 names stand in the botanical books as species.
• It is also estimated that probably 700 of these are really distinct, of these 700 it is only six that grow filler potatos at all, and the remainder all maintain their hold in the world, as most plants do, by means of their flower, fruits and seed.

The six tubes bearing species are

1. Solanum tuberosum
2. Solanum maglia, Schlecht
3. Solanum commersoni, Dunal
4. Solanum cardiophyllum, Lindley
5. Solanum jamesii, Torrey
6. Solanum oxycarpum, Schiede

Description

• The potato is perennial but as a crop it is treated as an annual.
• It is vegitatively propagated by means of tubes.
• Now it is also propagated by true potato seed (TPS).
• The tubler is an enlarged underground stem produced on the end of a stalons and not on the roots proper.

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Anatomy

The potato tuber has four parts which are morphologically known as

• The envelope or skin comprises the corky or outer covering of the tuber, corresponding to the bark of an above ground stem.
• The cortical laver: consists of the peripheral zone immediately beneath the skin. This zone or layers may vary from one-eigth to onehalf an inch in thickness.
• If exposed to light, this part of the tuber quickly turns green, and acquires a distinctly acrid
• Taste due to am accumulation of a poisonous substance, chemical known as Solanin.
• The external medullary area: Embraices the outer position of the strictly flashy part of the tuber.
• It is generally interested as including the densest position of the medullary area
• The internal medullary area includes the wacky and more transpucert central past of the tuber.

Physiology

• Studies have mainly been centering round the growth, development and tuberization.
• Ratio of Tuber/foliage, which is an index of the crop production efficiency of the plants, has been found to be higher under short days in plains than in the hills.
• Although there is no correlation between the relative tuber growth and net assimilation rate, there is a significant correlation in the tuber growth and relative growth of foliage.
• Potato varieties have been classified into qualitative and quantitative short day types with respect to tuber initiation.
• Kufri Sindhuri is a qualitative short day variety which is most sensitive to short day initially between 6-10 leaf stage.
• Light breaks of 5-6 min duration each at 4, 8, 12 hr. after commencement of the 16 hr inductive dark period has been found to inhibit tuber initiation.
• Similarly, a continuous night temperature of 20 deg C is favourable for tuber initiation while 30 deg, C is inhibitory.
• Night temperature 15-20deg C is the optimum range for pre-tubes initiation while 15 deg C was found close to optimum temperature for post-tuber initiation.
• Higher temperature reduce the leaf area, net assimilation and growth rate as well as chlorophyll contents of the leaves.
• Tuber treatment with CCC (cycocel) and gibberellic and afforded winter hardiness to potatoes.
• Knietin and mortphaution influenced the growth pattern of the leaves.
• Soaking of tubes in ascorbic and enhanced the yield by foliar sprays of ethrel at the tuber initiation stage increased the tuber number.

Post-Harvest Physiology and Technology

• The rate of tuber respiration decreased during the storage but increased sharply with sprouting.
• Storage in farm stores also increased the total sugars mainly sucrose in tubes.
• A simple and reliable bioassay technique for the absusic and in stored potatoes has been evolved.
• Several methods of breaking dormancy has been evolved right from peeling of potatos, application of carbon-di-sulphide; ethylene chlorohydrin and ammonium thiocyanate; combine treatment of ethylene chlorohydrin with thiourea and GA3; or purines or growth regulators viz, kinetin, and also by ethyl alcohol vapors.
• Sprout suppressants viz, TCNB, CIPC, MENA, MH, etc. have been tried as pr-harvest and tuber applications.
• Malic hydrazide has been found to be the most effective and persistent sprout suppressant chemical if it is sprayed on the crop.
• Further indications are available that post-harvest sprout suppressant like CIPC and MENA can be used for potatos stored in improvised country stores.

Stress Physiology

• A number of frost resistant solunums, viz, S. acaule,S/ stenotomum, S. demissum and cultivated diploids have been identified.
• Similarly studies on drought- stress are underway.
• Foliar application of abscisic acid has been observed to protect the leaves from water deficit for short periods.

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Vegetative Growth

Root

• The root of potato is adventitious.
• Arising from the base of a sprout
• Root growth is usually restricted to top layers at a depth 20 - 25 cm.
• In rich soils roots of some varieties may reach upto 90 - 100 cm.
• Such deep roots are found in potatos make an exception in dicotyledonous plants, which have tap root system.

Stem

• Stout, erect, flexuous, much branched, 30 - 60 cm long, slightly hairy, distinctly winged on the angles.
• The upper most part of the sprout develops into aerial stem or haulms.
• The aerial stains are angular, pubescent, or glabrous, green or purple,
• Main stem arising from first and high order buds, during growth of mother plant.
• Branches arising from below ground nodes on the main stem
• Slender leafy branches developing frequently from stems
• Above ground maxillary branches may have anthocyanin pigment and spread erect giving a close appearance or may spread out giving an open appearance.

Reproductive Growth

Flower

• Numerous, arranged in compound terminal cymes, with long peduncles.
• Each flower has 5 stamens, 5 sepals and 5 petals united for almost all their length.
• Most varieties bear infertile pollens hence fruit or berries are not formed
• The inflorescence is a compact racemose type born on the apex.

Pedicel

• Hairy, articulated about the middle.

Calyx

• Hairy, 1/4 th to 1/3 rd inch long, teeth deltoid cuspidate, as long as a little longer than the campanulate tube.

Corolla

• Dark lilac, subrotate, nearly an inch in diameter, pilose externally.

Segments

• Deltoid, half as long as the tube.

Anthers

• Bright orange yellow, linear oblong, nearly 1/4th inch long.

Filament

• Very short

Berry

• Perfectly globose, smooth, under an inch in diameter

Tuber

• It is a thickened stem having the cells mostly filled with starch as a reserve food for the new plants.
• The eyes are the promise of the future branches.
• The skin differs from the surface covering of the rest of the plant by being formed of a layer of delicate Cork with its accompanying lenticels (respiratory structure) like stem of other plants.
• Fibrous framework as well as pith, is continued from the leaf bearing steros into 1 ha tubes with relatively little change.
• Liquid more from part to part most rapidly through the tissue and not through the proper faith.