Potato

Morphology

• The aerial stems or hauls are angular, pubescent or glabrous, green or purple.
• They are herbaceous annuals, which may stand erect or procumbent or even prostrate.
• Depending upon their origin these hauls may be recognized as:
• Main stems arising from first and high order buds, during growth of mother plant.
• Branches arising from below-ground nodes on these main stems;
• Slender leafy branches developing frequently from stolons; and
• Above ground axillary branches.
• The hauls may have anthocyanin pigment in them when the tuber is green coloured.
• The axillary branches may spread erect giving a close appearance or may spread out giving an open appearance.
• The leaves are pinnately compound, with more or less petiolate leaflets.
• The shape, size, spacing of leaflets on the stem and the colour all vary in different varieties. As 12-15 leaves are present in an undeveloped bud (about 26 on a sprout 2 cm long) and possibly 40 is the maximum produced on any one axis.
• The leaves appear to be pubescent at the time of appearance.
• These leaves are alternately arranged on the hauls and leaflets are more or less opposite.
• Potato roots are small fibrous, adventitious which arise from the base or the sprout and they grow hardly upto 20-25 cm depth or in rare cases they may reach upto 90-100 cm depth in the soil.
• The type of roots found in potato make an exception in dicotyledonous plants, which have tap root system.
• The tubers morphologically are underground stems, which bear eyes, or buds that sprout and develop into hauls or branches.
• The tubers also contain lenticells, which are respiratory structures that occur in the stems of other plants.
• These tubers are formed on the stolen (appearing from the base of haulm or underground side shoots which are very similar to roots in early stage) tips.
• Most of the tubers which grow to harvestable size are formed within a period of two weeks.
• However, stolons often continue to grow and branch after this time and new tubers are being continuously formed but they remain immature at tuber lifting time.
• The hormonal action associated with photoperiod results in tuberization and accumulation of photosynthates at the stolen tips causes tuber bulking.
• Application of growth promoters on hauls retards tuberization but use of growth retardant on foliage accelerates the tuberization.
• Rate of tuber bulking depends upon its location as those found on the stolons use to grow but those found on the apex of the hauls or the axially tubers found in the axis of the leaves on the stems remain small.
• Similarly the exposed underground tubers also do not accumulate starch and remain smaller because they synthesize anthocyanin/chlorophyll and start performing photosynthetic activities like leaves.
• They become bitter in taste and are harmful or lethal, if consumed.
• The inflorescence is a compact racemose type which is borne on the apex.
• The flowers are perfect, self pollinated, and are purplish to white in colour according to the varieties.
• Most of the varieties of potato bear infertile pollen, therefore, formation of fruits or berries do not take place.
• The seeds are formed in berries but mostly they are not viable and have poor germination, therefore, use of seeds is restricted to initial testing and multiplication after breeding work is over.

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