When potato producers talk about seed, they mean a tuber, a vegetative seed, not botanical. Potato tuber is a modified stem with a water content of 70-75% and the remaining 25-30% of dry matter. It has buds, from which the new growth begins.
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What is potato tuber
Tuber - part of a plant that plays role in year-round growing season. As a storage of energy and nutrients, it serves to restore growth during the next growing season and as a means of asexual reproduction.
Strictly speaking, this is the tip of the underground stem, called the rhizome, which swells with nutrients.
The plant uses stored energy to support new shoots, thereby ensuring the survival of the species. It helps the plant to gain a foothold in the soil, as the roots do.
Tuber Definition
Potatoes are a stem tuber with parts of a normal stem (including nodes that are called buds or eyes) and an internode. By structure, each node has a leaf footprint, is able to germinate and grow into a new stem.
The plant is grown from whole and sliced potatoes, and the number of stems obtained from the planted specimen, depends on the number of eyes and its physiological age.
The kidneys are arranged in a spiral, starting at the end opposite to the point of attachment to the stolon. The terminal bud appears at the far point of stolon attachment, demonstrating apical dominance, just like a normal stem.
Inside the tuber is filled with starch stored in an enlarged parenchyma, like cells. The inner part has a cell structure typical for any stem (core, vascular zones and cortex).
How to form a tuber
Stem Tuber formed from thickened rhizomes (underground stems) or stolons that develop from the lower leaf sinuses on the stem and germinate into the soil.
Stolon lengthens over long days when there are high levels of auxins that prevent the growth of stolon roots. Before a new potato formation begins, stolon must be of a certain age.
The leaves, as the plant grows, produce starch,which is transported to the ends of underground stems (stolons). They thicken, forming several tubers located closer to the soil surface.
Their swelling occurs when the plant begins to invest in them most of its resources. Tuber formation is completed when soil temperature reaches 27 ° C. Potatoes are considered the culture of the cold season.
Pests and diseases
Late blight
It remains a serious problem for potatoes. The disease caused by the phytophthora mycelium, Phytophthora infestans, is rapidly spreading in foliage and potatoes. In temperate regions, soil or plant debris harbor the pathogen between seasons.
It survives in infected specimens that remain in the soil since last season. Seed pieces can also be infected and contain the pathogen. When new shoots from infected seeds appear, the fungus infects and thensporuliruet on new growth.
Sporangia
Microscopic, asexual spores that the pathogen produces. Under favorable environmental conditions, spread through the air or water. They land on foliage and at low temperatures and sufficient moisture they form and release zoospores migrating over the surface of the wet leaf.
Each zoospore eventually germinates in the indicated conditions and sends the germ tube to the leaf tissue. Penetrating into the epidermis in several areas, causes small brown spots. They quickly expand into large rot.
Common scab
Infection of potato with phytopathogenic Streptomyces scabies. Signs of infection appear on the surface with cork formations brown irregular shape in diameter up to several millimeters.
The disease does not affect the yield, although it reduces its quality. Infected potatoes are edible, the quality and taste of the flesh is the same as in healthy specimens. The reason for the common scab is the lack of water when growing the plant.
Silver scab
Caused by the pathogen Helminthosporium solani.Light brown spots appearing on the tuber alter the permeability of the skin, which leads to shrinkage and loss of water. Ideal conditions for the spread of the disease - high temperature and high humidity.
Powdery scab
Caused by the Spongospora subterranea pseudo mushroom f. sp. Signs include slight damage. (white growths) early diseaseprogressing to bright pustules (in the form of warts) on the surface of tubers.
With maturation, they become prominent, crack, forming ulcers filled with a brown powdery mass.
Oosporosis or scab tuberculate
The causative agent is Ascomyceteum mushroom, Polyscytalum pustulans, which affects the eyes on seed tubers.
Pests
Insectsthat transmit diseases of potatoes and damaging plant:
- Colorado beetle;
- potato moth (fluorimea);
- big aphid;
- nematode.
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- Colorado beetle
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- Fluorimea
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- Potato aphid
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- Nematode
Potato structure
Potatoes are an herbaceous perennial plant, depending on the variety, growing to 100 centimeters. The leaves die off after flowering, fruiting and tuber formation. The flowers are white, pink or purple with yellow stamens (the skin of the tubers depends on the color of the flower).
Culture mainly cross-pollinated by insectsbut also self-pollinated. The signal for the formation of tubers, as a rule, is a decrease in the length of daylight, but in commercial varieties this trend is minimized.
Potatoes include:
- ground part of the plant (or tops): a branching shrub consisting of several stems (from 4 to 8);
- leaves dark green intermittently—unmatched—pinot—dissected, spirally arranged on the stem. Each leaf is represented by the midrib (axle), pairs of lateral opposite lobes, between which there are lobules and in turn between them - dochki (the number depends on the age of the leaf), an unpaired lobe is placed on the top of the leaf;
- flowers bisexual and have the main parts: calyx, nimbus, male element (staminate) and female element;
- stolonsforming the adventitious roots in the nodes, and new plants from the buds.
What are the fruits of potato
When faded, the plant produces small green fruits that resemble green cherry tomatoes. Plants that grow from tubers are clones of parents.
New varieties are grown from seeds, which are then propagated vegetatively. Fertile fruits contain more than 200 potato seeds in tetraploid varieties.
Root crops, rhizomes, tubers, root tubers belong to the root systemthey should not be confused with the fruits. In botany, true roots (roots and root tubers) are distinguished from non-root (tubers, rhizomes).
| Root vegetable | plant organ increased to store energy in the form of carbohydrates;
associated with the root system (as the first part of the name says), not a fruit (the second part of the name is incorrect from a biological point of view) |
| Rhizome | modified underground stem of the plant with adventitious roots, rudimentary leaves, and axillary buds |
| Tuber | shortened shoot, modified to store energy (carbohydrates) or water |
| Root tuber | thickening of the roots (main or accessory) as a result of the deposition of nutrients for the stock |
Stolon is similar to the rhizome, but, in contrast, is the main stem of the plant. Shoots from the stolon develop from the existing stem, have long internodes, and in the end form new shoots.
Biological features of culture
From planting to ripening, the period ranges from 80 to 150 days, depending on the varieties. The life cycle of potatoes is characterized by initiation and growth, followed by a period of rest, finally, germination, leading to the next vegetative generation.
Germination start after a period of rest is accompanied by increased cellular metabolism. Seedlings appear from the kidneys (eyes).
Following up are formed everything vegetable parts. Photosynthesis occurs. The first and second stages last from 30 to 70 days depending on the planting date, soil temperature and other environmental factors, the physiological age of the tubers and the characteristics of specific varieties.
Tuber formation occurs approximately 30 to 60 days after planting seed tubers, from lateral subsurface buds developing at the base of the main stem, which, when underground, develop into stolons due to diagravropropic growth.
When conditions are favorable for the initiation of tubers, the elongation of the stolon ceases, and the cells located in the core and cortex of the apical region of the stolon expand first and then divide longitudinally.
The combination of these processes leads to swelling of the subapical part of the stolon. This phase is associated with flowering (but not always).
In the process of expansion tubers accumulate carbohydrates (mainly starch) and proteins. Reducing overall metabolic activity, they behave like ordinary storage vessels.
Tubers are harvested from 90 to 160 days after planting, depending on the varieties, production area and marketing conditions. Starch typically accounts for 20% of the fresh weight of a mature tuber.
After potato vines die off, the tuber's peel thickens and hardens (sugar turns into starch), which provides greater protection of the tubers during harvest, including by blocking the entry of pathogenic microorganisms into them.
Although the rest period is determined by the absence of visible growth, dormant meristems remain metabolically active, only the rate of many cellular processes is suppressed.
The chemical composition and nutritional value of potatoes
Tuber contains on average about 78% of water, thus, only the remaining 20% have direct nutritional value. Carbohydrates (18.4%) are the most abundant nutrients of potatoes, represented by starch and some soluble carbohydrates of dextrose, sugar.
In young tubers, a large proportion of sugars and less starch. But the longer it is in the soil, the more the starch content increases. As the germination of the starch turns into soluble glucose.
Sometimes you can hear that the potatoes are indigestible due to the high content of cellulose. In fact, such criticism has no basis. Cellulose content is less than 0.5%, as in many grains and vegetables.
Fat or ether extract appears in insignificant quantities, it can be almost ignored when discussing the nutritional value, especially since most of it is in an inedible peel in the form of a wax-like body.
Potato proteins are divided into three groups: patatin, protease inhibitors and high-molecular proteins. Patatin glycoprotein accounts for about 20% of the total amount of soluble protein in potatoes. Patatin exhibits enzymatic activity, plays a role in protection against pests and pathogens.
Non-protein forms of nitrogenous substances in potatoes are asparagine and a small amount of amino acids. It is possible that they promote digestion or serve a similar purpose.
The most important minerals contained in potatoes are potassium and phosphoric acid compounds. There are several organic acids (citric, tartaric, and succinic), which differ in tubers of different ages and in some take into account the taste of potatoes.
Potatoes are a good source of vitamin B6 and a good source of potassium, copper, vitamin C, manganese, phosphorus, niacin, dietary fiber.Contains many phytonutrients with antioxidant activity. Among these important health promoting compounds are carotenoids, flavonoids and caffeic acid.
Potato application
In the modern world, potatoes not only used for food, including the production of alcoholic beverages.
Among the hundreds of other ways to use potatoes:
- starch in the food industry is used for the production of thickeners, in the textile industry - adhesives and for the manufacture of paper and boards;
- researched to obtain polylactic acid for use in the production of plastic products; starch serves as a base for biodegradable packaging;
- potato peel mixed with honey - folk remedy for burns in India. In burn centers, countries are experimenting with a thin outer layer of tubers to treat burns;
- investigated by scientists due to its clonal nature, sequential tissue parenchyma, low metabolic activity.
Cultural History in Europe and Russia
The Spanish conquistadors first encountered potatoes when they arrived in Peru in 1532 in search of gold. After the arrival of potatoes in Spain in 1570, several Spanish farmers began to grow them on a small scale, mainly as food for livestock.
From Spain, potatoes spread to Italy and other European countries in the late 1500s, although initially from the people he did not receive a warm welcome.
In northern Europe, potatoes were grown in botanical gardens as an exotic novelty. The introduction of potatoes in Russia is traditionally associated with the name of Peter the Great.
According to another version, Catherine the Great ordered the citizens to start cultivating the tubers, but the majority of the people, supported by the Orthodox Church, who argued that potatoes were not mentioned in the Bible, ignored this indication.
Until 1850, potatoes were not widely grown in Russia.until Nicholas I began to implement the order of the Empress.
Potatoes - an important model of the plant. It has several biological features that make it an attractive model to study. Like many other important crops, potatoes are polyploid. The effect of polyploidy on crop production is still to be determined, but its prevalence in crops provides certain advantages.