Seed production capability of monocotyledonous and dicotyledonous weeds in segetal and ruderal habitats

The main cause of wide presence of weeds in segetal and ruderal habitats is their high seed production capacity. It defined in expressly establishing field experiments, in industrial sowings, in segetal and ruderal habitats of steppe zones of Ukraine. It is determined that average fruitfulness of weeds in ruderal habitats was larger, than in segetal habitats by 3.8 times, and indexes of the maximum fruitfulness – by 4.0 times and reached accordingly 7028 and 9345 pieces, and 20112 and 98337 pieces. In segetal habitats monocotyledonous species of weeds on seed production on conceded dicotyledonous species by 2.9–3.7 times, and on ruderal habitats – by 9.8–10.5 times. Average seed production of monocotyledonous plants made up accordingly 3594 and 5660, and dicotyledonous – 12417 and 55629 pieces of seeds from one plant. Most species of monocotyledonous weeds (56,1 %) formed on one plant from 1 to 10 thousand pieces of seeds, and dicotyledonous weeds (37,9 %) – more than 10 thousand pieces of seeds. In segetal habitats the maximum seed production had families Asteraceae, Brassicaceae, Chenopodiaceae, Lamiaceae, and on ruderal habitats – Asteraceae, Chenopodiaceae, Caryophyllaceae, Apiaceae, Brassicaceae. The highest seed production the most widespread and abundant in sowings and on ruderal habitats had weeds: Convolvulus arvensis L., Ambrosia artemisiifolia L., Cynodon dactylon (L.) Pers., Echinochloa crus-galli (L.) P.Beauv., Eragrostis minor Host, Descurainia sophia (L.) Webb ex Prantl, Cirsium arvense (L.) Scop., Chenopodium album L., Amaranthus retroflexus L., etc. The greatest reserve weed seeds in soil in segetal habitats descended at the expense of species from genera Amaranthus, Galium, Cirsium, Setaria, and on ruderal habitats – Amaranthus, Chenopodium, Plantago, etc. In segetal habitats proof presence of weeds of genera with low seed production was sustained at the expense of their larger number of species, and genera with low number of species – at the expense of high seed production. In ruderal habitats – as at the expense of larger number of species, and their high seed production. The absolute maximum of seed production in segetal habitats have been reached at weeds of genera Amaranthus, Cirsium, Galium – from 3288 to 242266 pieces, and in ruderal habitats – Amaranthus, Chenopodium, Plantago – from 108903 to 1911683 pieces from one plant.


Introduction
In the Steppe zone of Ukraine over 62.2 % of its territory is occupied by sowings of agricultural crops (Zubets et al., 2004).Numerous researches testify that segetal habitats have strong feed infestation by monocotyledonous species which part in weed communities fluctuated from 3.5 to 63.2 % and dicotyledonous species -which specific mass varied from 5 to 99 %.The quantity of shoots in sowings reached 0.25-3.20 thousand pieces/m 2 , and on ruderal habitats -16-72 thousand piece/m 2 (Kempen, Graf, 1981;Ivashchenko, 2001;Mertens, Jansen, 2002;Tsykov et al., 2012;Kurdyukova, 2013).Century efforts of the man to get rid of them in sowings do not bring expected results.Weeds remain, as before, constant companions of crop plants and nontreated lands.The main cause of their wide presence at segetal habitats and on ruderal habitats is high seed production (Hosamini et al., 1971;Ivashchenko, 2001;Kurdyukova, 2015).It defines adaptability of the species to environmental conditions, character and rate of widening and range of various species of weed plants, composition and structure of phytocoenosis (plant association), a direction of successions in plant communities etc. (Schwerzel, 1970;Perron, Légère, 2000;Ivashchenko, 2001;Kosolap, 2004).The success of seed revegetation and constant presence of weeds at phytocoenosis is provided with enough of their seeds in soil.Entering of seeds in soil under the different data on 70-92 % was defined by level of seed production of weeds in the given field (Kosolap, 2004;Konoplia, Kurdyukova, 2013).Therefore, last years the problem of seed production of weeds attracts attention and presented in various research (Mertens, Jansen, 2002;Konoplia, Litvinova, 2007;Lutman et al., 2008;Borona et al., 2009;Kosolap, 2011;Hill et al., 2014;Kurdyukova, 2014;2015).However, there are not enough data available in literature on fruitfulness of monocotyledonous and dicotyledonous species of weeds in sowings and on ruderal habitats.

Materials and methods
Seed production of different weed species were recorded within 2007-2017 in segetal and ruderal habitats of Steppe zones of Ukraine.Samples of weeds in coenopopulations were covered all their morphological diversity.The area of record plots of seed production of small species or insignificant quantity of all weeds which were a part of community or synusia, made up from 16 to 100 m 2 , and at high density of generative individuals, and also neotenic and dwarf species (forms) -0.25-1.0m 2 , standing alone weeds with small frequency -1.0-10 thousands m 2 .Record plots on the large areas were evaluated by their diagonal, by criss-cross pattern or by «envelope» method, placing them through equal spacing from each other, using for their separation special metal frameworks (at the area 0.25-1.0m 2 ) or special cords with pegs (at the area 10-100 m 2 ).We use actual quantity of seeds or fruits which were produced by one specimen of the plant for one generation as seed production size.Average seed production was defined as quotient from division of the sum of quantity of seeds from each record plant on number of registration plants among samples.Average minimum (maximum) seed production was determined as quotient from division of the sum of the least (greatest) quantity of seeds from one registration plant in each sampling series on total number of samplings.Absolute (minimum) maximum seed production -as the least (greatest) quantity of seeds from one registration plant, fixed ever during all long-term period of researches.Weeds and seeds classification was made in accordance with the standard field guides (Maisurian, Atabekova, 1978;Kosolap, 2011;Flora SSSR, 1934-1960).

Results
It has been determined that average fruitfulness of monocotyledonous and dicotyledonous weed species in ruderal habitats was larger, than in segetal habitats by 3.8 times; indexes of the maximum fruitfulness -by 4.0 times and it was accordingly 7028 and 9345 pieces in segetal vs 20112 and 98337 pieces in ruderal habitats.In sowings of agricultural crops, the monocotyledonous species of weeds on fruitfulness of one plant conceded to dicotyledonous in 2.9-3.7 times, and on ruderal habitats -in 9.8-10.5 times.However, the seed production difference of monocotyledonous weeds which occurred in sowings, in comparison with ruderal habitats was smaller, made up on average indexes of fruitfulness of 43.2 thousand pieces and reached in ruderal habitats 55629 pieces, and in segetal habitats it was only 12417 pieces.The same dependences were determined in relation to the minimum and maximum seed production (table 1).High seed production was typical only for species of monocotyledonous plants which had high stems -Phragmites australis (Cav.)Trin.ex Steud., Leymus racemosus (Lam.)Tzvelev, or they were well tillered and formed the considerable quantity of productive stems, in particular Cynodon dactylon (L.) Pers., Echinochloa crus-galli (L.) P.Beauv., and Eragrostis minor Host.
Among dicotyledonous weeds the quantity of species which formed up to 1 thousand seeds, was lesser in comparison with monocotyledonous and made up 21.7%.It was mainly early-spring ephemers and ephemeroids, in particular Veronica hederifolia L. and V. praecox All., Erodium cicutarium (L.) L'Hér., Ceratocephala testiculata (Crantz) Roth, and Myosurus minimus L. The species ratio which formed from 1 to 10 thousand and over 10 thousand seeds per plant was almost equal -37.9%.Among them there were such widely distributed and abundant in sowings and ruderal habitats species of weeds like Convolvulus arvensis L., Ambrosia artemisiifolia L., Descurainia sophia (L.) Webb ex Prantl, Cirsium arvense (L.) Scop., Chenopodium album L., and Amaranthus retroflexus L.
Consequently, the monocotyledonous and dicotyledonous weeds were characterized by the highest fruitfulness in ruderal ecotopes.Dicotyledonous species of weeds, irrespective of habitats exceeded the monocotyledonous species by 3.5-9.8times concerning the seed production level.In segetal habitats specific mass of the most prolific dicotyledonous species from Asteraceae and Lamiaceae with average seed production more than 10 thousand pieces per plant, reached 39.2 %, whereas on ruderal habitats these and others high fruitful weeds occupied just 45.6 %.Seed production of representatives of Seed production capability of monocotyledonous and dicotyledonous weeds Ukrainian Journal of Ecology, 8(1), 2018 Euphorbiaceae, Fabaceae, Boraginaceae with specific mass in segetal habitats of 17.1 %, and on ruderal habitats -1.9 %, did not exceed 500 pieces.
The weeds of all dominant families of Dicotyledonous which occurred on ruderal habitats had more seed per plant than on segetal habitats -it were higher by 1.This variation was more larger in agricultural crops.So, the genera which included 4-5 species, formed on average from 111 (genus Vicia L.) to 1041 (genus Atriplex) seeds per plant that explains their rather low frequency and low abundance in sowings.
At the same time, the plants of Amaranthus L., Galium L., and Cirsium Mill.(which have 2-3 species) formed on average from 14 to 95 thousand seeds per plant and were usual weeds with the high abundance in agriculture fields.
The maximum seed production of most weeds from dominant genera was from 5 to 25 thousand seeds, whereas the weeds from Amaranthus had over 100 thousand seeds and weeds of Vicia and Euphorbia -just about 1 thousand seeds (table 3).We suggest that low seed production of some weed genera in segetal habitats was compensated by their high species number, and poor species diversity of some genera -by high seed production.The seed production of weeds was considerably higher in ruderal habitats and this was true for Euphorbia, Atriplex, Vicia (5 species), they have seed production by 1.7-4.1 times higher.The Fruitfulness of Chenopodium weeds (9 species) exceeded 786 thousand seeds per plant, Amaranthus (3 species) -717 thousand seeds.The other genera had also high seed production, for instance, Plantago L. -21.5 thousand of seeds, Carduus L. -9.5 thousand of seeds, Lamium L.-5.4 thousand, and Digitaria Hall.-5.0 thousand of seeds (Table 4).The maximum fruitfulness of weeds of all genera, except for Euphorbia, exceeded 1 thousand seeds per plant; weeds of Plantago had 81.0 thousand seeds, Chenopodium -115 thousand, and Amaranthus -1454 thousand seed.
The absolute maximum of seed production of weeds in segetal habitats did not exceed 32.3-34.6 thousand seeds (Cirsium, Galium), for Amaranthus this was 242.3 thousand seeds, whereas on ruderal habitats the fruitfulness of most weeds of exceeded 10 thousand seeds (Carduus, Lamium, and Digitaria), Chenopodium -267.4 thousand, Plantago -108.9 thousand, and Amaranthus -1911 thousand seeds due to absence of the competition with cultivated plants.

Conclusions
The maximum seed production in the all habitats was formed by dicotyledonous species of weeds.In segetal habitats the highest seed production was registered for the families Chenopodiaceae, Lamiaceae, and Brassicaceae; in ruderal habitatsfor Asteraceae, Chenopodiaceae, Caryophyllaceae, and Apiaceae.The greatest reserve of weeds in soil of segetal habitats caused by Amaranthus, Galium, Cirsium, Setaria, and Digitaria, and in ruderal habitats -by Amaranthus, Chenopodium, and Plantago plants.

Table 2 .
3-1.8 times (for families Lamiaceae, Euphorbiaceae), by 3.7-8.8times (Asteraceae, Chenopodiaceae, Fabaceae, and Caryophyllaceae), and even by 11.4-20.3times (Boraginaceae, Apiaceae), whereas species of family Poaceae had more seed just by 1.75 times.So, Asteraceae weeds being the most species abundant formed on average 11.4 thousand seeds per plant in segetal more than 1000 thousand seed in ruderal habitats (this was 19.6 % and 19.4 % families respectively).The maximum fruitfulness was accordingly 20.7 and 176 thousand seeds per plant.Seed production of Asteraceae families, like Brassicaceae and Chenopodiaceae was similar (table 2) Seed production of weeds of dominant families on segetal and ruderal habitats, seeds per plant

Table 3 .
Seed production of weeds of the largest genera in segetal habitats, seeds per plant

Table 4 .
Estimated numbers of seeds produced by the largest genera of weeds in ruderal habitats