Movement and redistribution of nutrients. A direction of movement of nutrients on floeme

you are: Movement and redistribution of nutrients

In sitovidnyh tubes is present not only sucrose, but also others of sugar, amino acids, hormones and mineral substances, the truth, at smaller quantity. If on ksileme moving of its contents occurs exclusively from roots to leaves on floeme outflow is observed from the donor (a source of synthesised products) upwards or downwards to any point named an acceptor, i.e. A place where photosynthesis products are consumed or reserved. Sahara are necessary for growth of roots, tops of runaways and young leaves. They are transported also to roots and runaways where are postponed in a stock, or to seeds and fruits where there is their transformation into the substances necessary for growth of the subsequent generation. At some kinds as acceptors special bodies of storage, such, as tubers, rhizomes or bulbs can serve. When sucrose will reach these fleshy reserving fabrics, it usually turns here to insoluble starch that prevents formation of osmotically active solutions with high concentration. Later starch in these fabrics passes in sucrose and is exported to a new place of consumption.

Moving of sugars on floeme from the donor to an acceptor has been shown by means of a method of inclusion of a radioactive label. Radioactive dioxide of carbon or sucrose put on sheet of any plant and through some time interval a plant cleaned, dried up and placed on a x-ray film. There, where was radioactive 14С, on a film there was an image of black colour. Such way parts of a plant which receive sucrose from the fed up sheet easily come to light. as a rule, all consuming bodies are provided with the accessible source nearest to them. Therefore the uppermost photosynthesizing leaves supply growing kidneys and the youngest leaves. The bottom leaves provide roots, and the leaves which are close to fruits, - these fruits. At a perennial plant at which growth is observed mainly in the beginning of the vegetative period, all leaves supply with sucrose reserving fabrics located in different places in the end of a season, providing creation of large supplies of nutrients for a following period of vegetation. Absolutely clearly that movement of substances on floeme has no certain direction unlike their movement on ksileme. In the bottom part of a stalk this movement is usually directed downwards to roots. In other parts of a stalk the movement direction depends on interposition of the donor and an acceptor. Besides, the transport direction can change in dependence both on age of a plant, and on a season.

Researches with use corresponding mechenyh the dissolved substances have shown that transport on floeme can occur simultaneously in two directions. This visible ' a two-orientation ' grows out of a unilateral current in separate, but adjacent sitovidnyh the tubes connected to various donors and acceptors. The movement direction on floeme is defined exclusively by an arrangement of a place of consumption of nutrients concerning their source. Together with transported water and sucrose from the donor to an acceptor dvizhutsja and other connections. So, for example, rostovye the substances put on leaves, move together with a sucrose solution to a place of its consumption. Importance of this process is illustrated by a following fact. Some rostovye the substances put on leaves, being in the dark, do not move for sheet limits. But if on sheet put sucrose or shine it rostovye substances start to move.

Accurate representation about movement of substances from the donor to an acceptor on floeme is important for having at use of system pesticides (insektitsidov, fungitsidov, herbicides) and research of their efficiency. System name pesticides which move in a plant on ksileme or floeme or on both systems simultaneously. The pesticides moving only on ksileme, do not fall outside the limits sheet on which they are put. They are redistributed on all plant only after their entering into soil and absorption by roots. If insektitsidy or fungitsidy are transferred exclusively on floeme they will operate more effectively at dispersion on leaves. Such protective substance will move with a stream of a solution of sucrose from sheet to young developing runaways and to provide their constant protection. Floemnyj transport provides also continuous movement of protective substances from leaves finishing growth to new developing runaways until these substances will not collapse a plant. That herbicide with peak efficiency operated against weeds with well developed system vegetativno breeding stolonov or rhizomes, it should move on floeme. Such herbicide moves from sheet, a place of its drawing, to sucrose acceptors in growth points stolonov or rhizomes, as results, to their destruction. In essence one of the main problems, facing to the researchers creating new herbicides, consists not in research of toxic chemicals, and is faster in finding such herbicide which would have time to reach growth points stolonov and rhizomes before it will destroy spending system floemy.

Thanks to a combination ksilemnogo and floemnogo transport on a plant the set of various substances, including mineral elements, nitrogenous connections and vegetative hormones (fig. 8.2) circulates. Mineral ions, for example, at first are absorbed from soil, and then transported in an elevated part of a plant mainly on ksileme. In process of ageing of leaves some mobile elements are deduced from them (such, as To +, Н2РО4-, Mg2 +) which with a stream of transported sucrose are transferred on floeme to an acceptor.

At a lack of nutrients these elements can be again directed to growing runaway therefore it can remain rather healthy whereas older leaves are exhausted and find out symptoms of shortage of those or other substances.