Some features of cerials regrowth.
Cereals (Poaceae) form the basis of most of the meadows of all phytogeographical zones due to high level of adaptability . After mowing or grazing, cereals grow and restore their aerial mass.. Growing up herb is called aftermath, and property of plant to form aftermath is called aftermathability or aftergrowth capacity. Thanks to plant's aftermathability, during the summer one can use hayfield twice, while the pastures can be used repeatedly. In hayfields and pastures, aftermath is mainly formed due to regrowth of short shoots or formation of new shoots from the buds. In plants with short shoots after cutting or grazing, greater leaf surface remains near the soil surface, as compared with plants having elongated shoots.
Cereals regrowth features are still poorly studied, while available publications reflect more regrowth features of tropical and subtropical crops [1,7,8,9,15,3,10]. In this regard, the study of the cereals regrowth is of particular interest since cereals are characterized by diversity of biomorphes, and in many areas constitute basic economic and botanical group in pasture harvests [2,4,5,6].
The aim of our research was to study some features of the cereals regrowth. The objective of the research was to form the cereal groups depending on the regrowth and to study nutrient dynamics that accompanies this process.
For the experiments we used economically most important feed cereals. Route surveys and expeditions, which accounted for a significant part of our work, were carried out in the territory of the Republic of Mordovia.
Besides, stationary observations of cereals were conducted as well by continuous sampling and determination of biometric indicators. In some experiments, we extracted whole plants (up to 10-12 plants of each type) every 15 days, described them and recorded obtained material for detailed study. The research technique was based on methodology offered by I.G. Serebriakov .
Biochemical characteristics were studied by conventional techniques. Data on the dynamics of sugars and protein (their increase or decrease) served the main indicator of the metabolism intensity in plants. All parameters were determined upon completion of the formation of individual phytomers (by fully grown leafs) before transition of plants to the tillering stage.
Despite the large diversity in the formation of buds by species, there is certain regularity in nature of cereal regrowth, which manifests itself primarily in the partial contribution of various groups in buds to the process of plant formation. This is evidenced by the experimental data collected in summer in Mordovia (grass was cut at a height of 6-8 cm followed by counting the number of shoots formed per 100 regrown shoots in 5-6 replicates) (Fig. 1, Table 1).
groups of buds:
After exclusion, cereals grow in different ways: some species are regrown mainly due to aboveground buds, others--by underground buds. For example, cereals, forming rhizomes (Bromopsis inermis, Calamagrostis epigeios etc.), grow mainly due to buds of underground structures, whereas species having in the structure a large number of shortened stolon-type shoots (Agrostis stolonifera L., Phleum pratense L.i etc.), are regrown by aboveground buds. Apical buds are of great importance in 44% of the studied species in Mordovia. Major role in formation of aftermath belongs to these buds in species, such as Deschampsia cespitosa (L.) Beauv., Dactylis glomerata L., Phleum pratense and others, whose structure is dominated by short shoots. Importance of lateral buds of diageotropic shoots in formation of the aftermath is small, despite the presence of these structures in many species. They have significant role in regrowth of stolon-type cereals.
Lateral buds of apogeotropic shoots are very important in forming the aftermath of many cereals. For example, in Mordovia these buds gave about 67% of the shoots in Agrostis stolonifera. They play a major role in plant formation of tall-growing herbage cereals, not forming short shoots (Bromopsis inermis, Calamagrostis epigeios etc.), which is more than 20%. Importance of the bugs in tillering zone in cereals plant formation is quite high, though their involvement in grass formation strongly varies by species. The highest number of shoots is formed by buds of tillering zone in species, such as Dactylis glomerata, etc. The proportion of rhizome buds in the formation of aftermath of tall-growing cereals account for up to 50%.
Under natural conditions of Mordovia, the proportion of buds in diageotropic shoots, contributing to formation of the cereals aftermath, was also low. This is due to more intense capture of cross-border area by each specimen due to rising summer temperatures (up to 30[degrees]C and above), improved vegetation conditions for cereal with C4-type of photosynthesis, and weakening competition from the temperate species, vegetated in early spring. Summer high temperature favors the development of heat-resistant crops, which is able to grow rapidly by rooting at the nodes of stolon-type shoots.
Structure analysis of the cereals aftermath shows that differences in the regrowth of individual species are associated with the peculiarities of their tillering: the more types of shoots in the structure, the more groups of buds are taking part in the formation of the aftermath. Regrowth of individual cereals after defoliation depends on the fraction of truncated and stolon-type shoots, whose growth buds are usually below the level of exclusion. Cessation of shoot growth occurred whenever cut accounted below the top node. Removal of the upper part of the shoot, where the active meristem is concentrated, paralyzes its growth and even leads to death. During the growth of the parent shoot many buds of tillering zone, as well as aboveground phytomers, are at rest and do not burst. Extraction the top initiates growth of previously dormant lateral buds. Removing the apex of the parent shoot activates the growth of shoots from rhizomes and stolon buds.
Thus, depending on regrowth nature, cereals can be divided into the following groups: 1) cereal spices regrowing at close cut mostly by underground buds, not forming short shoots and losing the entire leaf surface after exclusion (rhizomatous species); 2) cereal spices forming short shoots with long sheaths (their apical buds are placed on the soil surface and often are excluded), which partially retain the assimilation surface after the cut and regrowth by preserved apical buds and buds of tillering zone (tall-growing and loose bunch-grass species); 3) cereal spices regrowing mainly by apical buds, showing up by preserving a significant part of the leaf surface after exclusion (stunted pasture cereals).
Cereal regrowth nature is determined also by the amount and composition of nutrients in reserve organs, which are spent on breathing and building new structures, as indicated by many authors . Most dynamic agents are stubble carbohydrates, which are presented by assimilates and used as energy source to form new organs. Hydrolysis of carbohydrates of other organs occurs somewhat later.
The intensity of vegetative renewal of cereals, as well as other plants, is determined, especially in the first period after defoliation, by amount of reserve constituents accumulated by each plant . This is also clearly demonstrated by our investigation of the dynamics of protein (Fig. 2), monobasic saccharides, disaccharides and starch after cutting grasses in summer in Mordovia. Immediately after cutting, a decrease of soluble carbohydrates was observed first of all in the stubble, and then in the underground organs. With the growth of leaves and enhancement of photosynthesis, the amount of soluble carbohydrates increases. First three days after the exclusion are characterized by sharp decrease in the content of carbohydrates in the elevated structures of all kinds, while at the underground portion their number varies slightly. Obviously, during this period, hydrolysis processes, as well as carbohydrates consumption for breathing is quite intense. Growth processes are still poor; apical buds in all types of plants give just first folded leaves. The protein content is virtually unchanged in all structures. Early regrowth of short shoots and the reawakening of the surviving lateral buds of apogeotropic shoots can be explained by rapid mobilization of reserve constituents in stubble.
Six days after mowing, during the explication of the first leaves in the aerial part, the content of mono-and disaccharides was reduced to a minimum in all species, and that of protein reduced by 2-3 times; the amount of starch markedly decreased in underground organs, especially in Dactylis glomerata. A slight decrease of mono- and disaccharides in the roots is apparently due to increased hydrolysis of starch. A decrease of the protein was observed as well. These data indicate that the reserve constituent are still consumed, because photosynthesis products, formed in young leaves, obviously are not sufficient for the formation of new shoots. Nine days after the cut (the second leaf expansion) further decrease in the amount of starch was noted that is associated with increased consumption of plastic material to build new organs and partial atrophy of the old roots. By the 12th day the new shoots of all cereals had 2-3 expanded leaves, while in Bromopsis inermis the number of leaves was 4; decreased water-soluble sugars and starch was noted as well. Fifteen days after mowing, the growing shoots showed the fourth and sixth leaves; this was followed by stabilization in carbohydrate content. In some species an increase of simple sugars was observed. The latter is obviously associated with the arrival of sugars from the aerial organs, where their generation has significantly enhanced due to increased photosynthesis.
Different variation in the content of carbohydrates and their fractions by species in the period of aftermath regrowth can be explained to a certain degree by data on the reserve organs ratio in the species studied (Fig. 3). On average, number of roots and rhizomes per 100 shoots of Phleum pratense is higher (by weight) than that for other species. Therefore stabilization in content of reserved carbohydrates for this specimen was noted as early as after 9-12 days after cutoff. If, for example, per 100 shoots of Poa pratensis L. s. l. there is just 115 g of dry matter of reserve organs, for Phleum pratense this figure amounts to 409. Mowing noticeably affects on the ratio of the reseve organs. The greatest changes are exposed to mass indicators of stubble residues, as well as tillering and root zones. In Poa pratensis, whose roots are the most important source of the reserve, in two weeks after cutoff, the mass of active roots is reduced by more than twice; in Bromopsis inermis and Phleum pratense roots mass is reduced less noticeably that is obviously associated with the continuation of the vigorous activity of roots, formed by rhizomes. A high percentage of stubble residues in Poa pratensis is explained by continuation of their vegetation development after the cut due to the formation of side shoots.
Regrowth of plants depends on their biological properties, mowing time (grazing), growing conditions, and the degree of availability of plant's reserve nutrients. Analysis of the carbohydrates dynamics in storage organs of boreal cereals shows that their consumption in the first period after exclusion (intense breathing period) is higher than protein; stubble carbohydrates are consumed most actively; transition of the plants to the phase of intensive formation of new organs (6-9 days after the cut) is associated with the continuation of consumption of carbohydrates and a significant reduction in protein in the stubble and underground organs; stabilization of carbohydrates in reserve organs and some accumulation coincides in time with the formation of shoots with 3-4 leaves; increase of carbohydrate reserves in the reserve organs in the beginning takes place due to increasing of mono-saccharides and disaccharides. Thus, the available publications that mainly reflect the regrowth of tropical and subtropical cereals [1,7,8,9,15,3,10] are complemented by our research of cereals growing in temperate zone.
Our study is limited to determination of cereals regrowth, their tillering features and the formation of certain groups of buds. In terms of location and importance in the formation of aftermath after defoliation of plant formation, the buds are separated to five groups: apical, lateral buds of diageotropic shoots, lateral buds of apogeotropic shoots, buds of tillering zone, and rhizome buds, differing by biometric and biochemical characteristics.
A characteristic feature of boreal cereals is their high capacity for regrowth of lateral buds of apogeotropic aerial shoots. Cereals, belonging to the group of rhizomatous-stolon-forming and rhizomatous, differ by active participation in formation of aftermath of lateral buds of apogeotropic shoots (both rhizomes and stolon-type). Studies of the cereals regrowth by season, depending on the height and the cutoff frequency, may become possible prospects for future research.
The current work was carried out under the financial support of the Ministry of Education and Science of the Russian Federation at the expense of the Event #2 "Modernization of research and innovation process (content and organization)", as well as Strategic Development Program of Mordovia State Pedagogical Institute named after M. E. Evsev'ev for 2012-2016 "Pedagogical Staff for Innovative Russia".
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Alfiya Yunerovna Gorchakova
Federal State--Financed Educational Institution of Higher Professional Education M. E. Evsevjev Mordvian State Pedagogical Institute, 430027, Saransk, Studencheskaya street, 13, Russia
Received: 25 April 2014; Received: 20 May 2014; Accepted: 25 May 2014; Available online: 22 June 2014
Corresponding Author: Alfiya Yunerovna Gorchakova, Federal State--Financed Educational Institution of Higher Professional Education M. E. Evsevjev Mordvian State Pedagogical Institute, 430027, Saransk, Studencheskaya street, 13, Russia
Table 1: Regrowth of certain cereals in summer period Species Shoots formed by groups of buds, %, ([bar.X] [+ or -] [delta]): Life-form 1st 2nd Dactylis LB 69 [+ or -] 4.9 11 [+ or -] 0.6 glomerata L. Festuca RL 61 [+ or -] 1.0 -- rubra L. Phleum LB 2 [+ or -] 0.3 3 [+ or -] 0.4 pratense L. Deschampsia FB 87 [+ or -] 0.9 4 [+ or -] 0.4 cespitosa (L.) Beauv. Bromopsis inermis R 6 [+ or -] 0.5 -- (Leyss.) Holub, <<Penzenskiy-1>> Calamagrostis R 1 [+ or -] 0.1 -- epigeios (L.) Roth Agrostis RS 1 [+ or -] 0.1 18 [+ or -] 0.3 stolonifera L. Species Shoots formed by groups of buds, %, ([bar.X] [+ or -] [delta]): Life-form 3rd 4th Dactylis LB 1 [+ or -] 0.2 19 [+ or -] 1.3 glomerata L. Festuca RL 8 [+ or -] 0.5 31 [+ or -] 0.9 rubra L. Phleum LB 48 [+ or -]1.3 47 [+ or -] 1.1 pratense L. Deschampsia FB 1 [+ or -] 0.3 8 [+ or -] 0.7 cespitosa (L.) Beauv. Bromopsis inermis R 18 [+ or -] 0.7 50 [+ or -] 1.3 (Leyss.) Holub, <<Penzenskiy-1>> Calamagrostis R 30 [+ or -] 1.5 26 [+ or -] 0.7 epigeios (L.) Roth Agrostis RS 67 [+ or -] 1.5 3 [+ or -] 0.3 stolonifera L. Species Shoots formed by groups of buds, %, ([bar.X] [+ or -] [delta]): Life-form 5th Dactylis LB -- glomerata L. Festuca RL -- rubra L. Phleum LB -- pratense L. Deschampsia FB -- cespitosa (L.) Beauv. Bromopsis inermis R 26 [+ or -] 1.1 (Leyss.) Holub, <<Penzenskiy-1>> Calamagrostis R 43 [+ or -] 0.7 epigeios (L.) Roth Agrostis RS 11 [+ or -] 0.4 stolonifera L. Note: R--rhizomatous cereals; RS--rhizomatous-stolon-forming cereals; RL--rhizomatous-loose bunch-grass cereals; LB--loose bunch-grass cereals; FB--firm bunch-grass cereals.
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|Title Annotation:||Research Article|
|Author:||Gorchakova, Alfiya Yunerovna|
|Publication:||American-Eurasian Journal of Sustainable Agriculture|
|Date:||May 1, 2014|
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