THE SEED AND THE GERMINATION
THE SEED AND ITS IMPORTANCE
The appearance of the seed in the history of evolution has represented a turning point for the diffusion of spermatophyte plants (the most evolved type of plants, with visible reproductive organs).
The seed is the fundamental element for the propagation of the plant. It contains within itself a small plant in the embryonic state, characterized by the genes of both parents, and plays two very important functions: ensure the spread of the species in as wide a territory as possible, and be able to survive during the seasons and unfavorable conditions. This last capacity is called quiescence. In fact, the seed is able to remain vital for long periods if placed in the presence of conditions not favorable to its germination. Once its development is finished, the seed begins a phase of dehydration and the embryo inside it slows down remaining vital but without developing for a very variable period of time that can last even years.
In each type of seed we can distinguish three different constituent parts:
1 - Embryo: it is the result of the division of the fertilized egg cell. In it are recognizable a radicle, which is the principle of the future root system of the plant, on the opposite side a tiny feather that will become the apical part of the sprout, wrapped by the cotyledons, that is small embryonic leaves, which will immediately position themselves under feather (it will not yet be visible to the eyes) once opened. In the case of hot peppers the cotyledons are two (Dicotyledons).
2 - Endosperm: consists of tissues containing nutrients that are accumulated and will be necessary for seed development in the germination phase.
3 - Seed coat (testa): it is the wrapping that encloses and protects everything from atmospheric agents, prevents excessive dehydration or absorption of water or other substances.
Before germination the seed is in the quiescent state, it is very dehydrated (water is present in quantities between 5% and 10%), has a partial cellular disorganization and maintains an extremely slow metabolism. Germination is the process that begins with seed hydration and ends when the embryo radicle comes out of the seed coat. From this point on, the root and bud growth phase begins.
The conditions necessary to activate the germination process are:
- presence of water: with the imbibition of the seed begins its rehydration, the cell membranes reassemble and reactivate the proteins and enzymes that allow the embryo to be able to use the nutritive reserves contained in the endosperm. These will support growth in initial development.
- presence of oxygen: even if initially the process of recovery of the metabolism takes place in the absence of air, as soon as the seed coat breaks, oxygen can penetrate inside.
- right temperature: the seeds do not germinate below a certain temperature (which varies from species to species) and this affects both the germination speed and the quantity of seeds that can germinate.
Main stages of seed germination and bud growth
HISTORY OF PEPPER
The history of chili is very old and begins in Latin America.
We know that as early as 5000 BC. this plant was known and cultivated, and more generally its use as a spice was widespread in all pre-Columbian civilizations, especially Aztecs, Inca and Maya.
The pepper was brought to Europe by Christopher Columbus, following the discovery of America.
the Spaniards spread the new spice which, despite having a great success, immediately proved not to be a source of easy profits as had happened for the spices coming from the East. The chili plant in fact adapted very well to the European climate, and the ease of its cultivation made any form of trade with the land of origin useless. So it was that the pepper spread enormously, especially among the lower classes of society. It quickly became the spice most used by the people who could not buy expensive spices to give flavor to poor dishes, as well as to preserve food. The chili spread very much especially in the south of the continent and more generally in the warmer countries because of its ability to preserve food.
Representation of a chili plant with four fruits and a flower, carved on the obelisk of Tello, dated between 850 BC. and 200 a. C., and found on the site of Chavin de Huantar in Peru.
CAPSICUM ANNUM It is the most widespread species and the fruits can be both sweet and spicy. Unlike what is believed it is not an annual plant, in fact it is a perennial plant if it is grown with favorable temperatures. Examples of capsicum annum are the Jalapeno and Cayenna peppers
CAPSICUM FRUTESCENS The plant is native to South America and is perennial with spicy fruits. The best known varieties are: Tabasco and Malagueta.
CAPSICUM CHINENSE Plant originally from the Amazon region. The super hot chili peppers, the hottest in the world, belong to this species. Among these the most famous and widespread are the Habaneros.
CAPSICUM PUBESCENS Is a species native to Brazil, widespread especially in Central America, and is the most resistant to low temperatures. The best known variety is the Rocoto, famous for its black seeds.
CAPSICUM BACCATUM It comes from the regions of Bolivia and Peru. It includes many varieties. Some peppers of this species are for example the Aji Amarillo, the Aji melocoton and the Aji lemon. There are also two wild forms: Capsicum baccatum var. baccatum and Capsicum baccatum var. microcarpum, the latter known as Bird pepper.
THE GENUS CAPSICUM
The pepper plant, genus Capsicum, belongs to the Solanaceae family, and includes over 30 different species. only five of these are the best known and cultivated and can be easily distinguished according to the characteristics of the flowers.
CAPSAICIN AND SPICY
Capsaicin is a chemical compound, an alkaloid, present in the fruits of chillies and is responsible for most of the "spiciness". Capsaicin is produced by glands located between the inner wall of the fruit and the membrane that supports the seeds that is called the placenta. The latter is the richest part of capsaicin, while the seeds, contrary to what is commonly believed, are covered only on the surface by capsaicinoids but inside they are free.
Spicy is not one of the basic tastes, in fact sweet, salty, sour and bitter are each equipped with their own receptors, while the spicy acts by tricking the receptors of temperature, is the same thing that make some molecules, like menthol, on cold sensors. Capsaicin produces a burning sensation in the mucous membranes of the mouth because its composition allows it to interact with the VR1 and VRL-1 receptors, which under normal conditions are activated respectively at temperatures of about 43 ° C and 52 ° C.
In the cell membrane a channel opens and this allows the passage of calcium ions. They cause the transmission of a pain signal that reaches the brain. It is a virtual sensation of burning even if the pain seems real, in fact the temperature of our mouth does not change when we eat chili.
THE SCOVILLE SCALE
The Scoville scale is used To quantify the capsaicin contained in a chilli pepper.
It takes its name from its creator, Wilbur Scoville, a US chemist who developed the Scoville Organoleptic Test (SOT) in 1912. This test consists of diluting the chili extract in water and sugar, until the "burning" sensation disappears completely. tasting it. This test is very subjective and the degree of dilution, set equal to 16,000,000 for pure capsaicin was placed arbitrarily by Scoville. Today there are several more scientific methods to measure the spiciness of a chili such as the High-Performance Liquid Chromatography method, but the unit of measurement is still the Scoville Unit.