CC BY
34
UDC 582.736
VARIABILITY OF CHARACTERISTICS OF THE GENERATIVE ORGANS IN MEDICAGO L. GENUS
Kolyasnikova N.L., Doctor of Biological Sciences Perm State Agricultural Academy, Perm, Russia E-mail: kolyasnikova@list.ru
ABSTRACT
The characteristics that determine the reproductive potential of the nine species of the genus Medicago are studied. There is similarity in the variability of traits that determine seed production of a plant. The reasons of low realization of potential productivity of fruitification are defined.
KEY WORDS
Medicago; Fertility; Sterility; Seed productivity; Ovules; Variability of characteristics.
One of the directions of a creative heritage of N.I. Vavilov is his selection and genetic works. The principle of ecologic-geographical intraspecific differentiation, ideas about the centers of cultural plants origin make a scientific basis about an initial material in plants selection [1]. Alfalfa is the most important fodder agricultural crop. An important theoretical and practical value has a study of the productivity of alfalfa for a selection and seed farming. The plants of alfalfa possess enormous potential of fruit and seed formation, which consists of mortgaged on the plant of inflorescences, flowers and ovules in the ovaries of flowers. In spite of high potential possibilities, actual realization of biological potential of the productivity in all regions of crop cultivations is relatively low. It is very interesting to find out all reasons of low realization of potential efficiency of fruit formation.
MATERIAL AND METHODS OF RESEARCH
Researches were executed on the followings species of Alfalfa: Medicago cancellata Bieb. - alfalfa cancellated, 2n = 48; M. falcata L. - alfalfa falcate, 2n=32; M. glutinosa Bieb. -alfalfa adhesive, 2n=32; M. polychma Grossh. - alfalfa polychromatic, 2n= 32; M. sativa L. -alfalfa sown, 2n=32; M. cаemlea Lees. - alfalfa bue, 2n=16; M. difalcata Sinsk. - alfalfa South Kazakh, 2n=16; M. quasifalcata Sinsk. - alfalfa recurvirostral, 2n=16; M. trautvetteri Sumn. - alfalfa Trautvetter, 2n=16.
Plants grew on a experimental area of Priaralsk experimental station of All-Union Research Institute of Plant Breeding (the Aktyubinsk Region) and a botanical garden of Perm state university (the Perm Region). 280 samples were studied. 20 unpollinated and just blossomed flowers and 20 green beans set in the result of free pollination were taken from each plant of different species. In the ovaries of each flower the number of fertile and sterile ovules is defined. In sterile ovules the cells of epidermis nucleus, containing callose survive, and in ultra-violet light they give a yellow-green glow after processing with fluorokhrom [5].
Fertile and sterile ovules are undistinguished by their form and size. 11200 ovaries are analyzed. At the same time embryological research of mentioned species of alfalfa on temporally fixed material was conducted. About 5000 constant preparations made by the standard technique were studied [6].
RESULTS AND DISCUSSION
During long-term researches which were conducted since 1985, we tracked dynamics of a condition of ovules, since the moment of blooming of a flower to a stage of mature beans in different ecological conditions (table 1).
The average number of ovules’ ovaries at different species fluctuates from 5,85 at M. cancellata to 9,90 at M. polychroa. The average level of this one specie indicator in different years and in different ecological conditions doesn’t differ that allows us to consider this warning is hereditarily fixed. According to the number of ovules in ovaries among the studied species 2 groups are differed: yellow flowered, with number of ovules from 5 to 7 and blue flowered, which has much more ovules in ovaries, from 9 to 10.
Table 1 - Dynamics of condition of ovules in flowers of different alfalfa species
specie Number of ovules in ovaries, M±m
total sterile Fertile
unfertilized fertilized
Degenerated after fertilization seeding
M. cancellata 5,85±0,10 0,39±0,06 3,52±0,11 0,28±0,08 2,40±0,12
M. difalcata 6,79±0.15 0,96±0,08 3,85±0,15 0,76±0,12 2,92±0,18
M. quasifalcata 7,55±0,12 0,52±0,09 4,52±0,17 0,54±0,11 2,97±0,16
M. falcata 7,51±0,14 0,29±0,12 4,70±0,22 0,11±0,11 2,55±0,12
M. trautvetteri 9,02±0,13 0,58±0,05 5,31±0,16 0,52±0,07 3,48±0,12
M. sativa 9,75±0,15 0,94±0,10 5,60±0,18 0,23±0,05 4,23±0,19
M. cаerulea 9,63±0,14 0,20±0,14 5,49±0,33 0,57±0,11 3,74±0,24
M. polychroa 9,90±0,16 0,90±0,11 6,42±0,13 0,60±0,12 3,55±0,15
M. glutinosa 9,60±0,27 0,45±0,05 5,75±0,24 0,34±0.16 3,90±0,13
All investigated alfalfa species are characterized with the degradation of some ovules before pollination. The violations of the presence of two germinal bags s in one ovule; the absence of germinal bag structures are detected.
The average value of sterile ovules per ovary is not great (1 - 2 for different species) and in different years is not constant. Thus, this characteristic is not specific; it depends on ecological conditions, ovule position in ovary. In a whole ovule fertility is rather high.
According to the quantity fertile ovules are divided into three uneven groups: fertile but unfertilized; fertilized, but degenerate because of abnormal development of endosperm; fertilized, developing normal seeds. All species have large proportion of unfertilized ovules, on the average of 46,76% from fertile. Germinal bags in these ovules are matured and remain unchanged to 120 hours, and then their degeneration features are observed.
The part of ovules degenerated already being fertilized; they give puny defective seeds.
The share of such ovules varies at different species; it is insignificant and doesn't depend on position in ovary. One of the reasons of degeneration is violations in development the endosperm, being observed at a stage of a club-shaped germ. Endosperm kernels were exposed to pycnosis, and acquired phaeochrous clots form (when coloring by iron hematoxylin), then the germ degeneration began: outlines of cells got an ugly form, borders between them became unidentified.
Alfalfa plants were grown in similar conditions on allotments with regular watering. From data of Table 2 follows that the maximum potential seed efficiency is referred to M. caerulea, it corresponds to 19347,2 ovules per generative shoot. The minimum seed efficiency is referred to M. cancellata, it is 2110,4. Other species on number of being formed ovules per generative shoot are mediate. According to I. V. Vaynagy [2], we consider expedient to divide concept "seed efficiency" into two concepts: "potential seed efficiency" -number of ovules per generative shoot or species (ПСП) and "actual" (real) - number of seeds per generative shoot or species (РСП).
Real seed efficiency at the studied six long-term species was almost ten times lower than the potential. Its maximum value - 2422,3 - is registered at M. caerulea, the minimum -161,6 - at M. cancellata. That fact is interesting that alfalfa sown, holding an average position on number of inflorescences on generative shoot, flowers in an inflorescence ovules in ovary, comes out on top by quantity of the seeds corresponding to one bean, among other species. Undoubtedly, it is a result of long-term selection of alfalfa sown.
The percent of the ovules which have given seeds, varied from 32 at M. caerulea to 43 at M. difalcata. M. sativa on this indicator holds average position among other studied longterm species. It should be noted that at species for which the large number of ovules in ovary is genetically determined, further the smaller percent forms seeds.
Table 2 - Seed productivity perennial alfalfa species in the collection area of Priaralskaya
experimental station
species name, ploidity inflorescence number on shoot flower number in inflorescence ovules number in ovary bean number in inflorescence seed number in mature bean PSP RSP
M+m M+m M+m M+m M+m
M. cancellata, 6х 54+1 7+1 5,8+0,1 1,3+0,6 2,2+0,2 2110,4 161,6
M.difalcata, 2\ 62+2 12+2 6,8+0,2 7,8+0,7 2,9+0,3 5054,7 1405,8
M.quasifalca-ta, 2\ 79+2 11+1 7,6+0,2 8,9+0,6 2,9+0,3 7298,9 2017,6
M.falcata, 4x 104+4 6+1 7,5+0,1 5,8+0,8 2,7+0,3 5465,0 1647,2
M. caerulea, 2x 107+3 18+1 9,6+0,1 7,0+0,6 3,2+0,4 19347,2 2422,3
M.sativa, 4x 92+2 12+1 9,8+0,2 6,4+0,8 3,7+0,4 10573,2 2181,5
So at M. caerulea on the average 9,6 ovules are formed in ovary, but only 32% from them give seeds. On the contrary, at M. difalcata where on the average 6,8 ovules in ovary, 43% ovules are developed further in seeds. Thus, selection of genotypes defining a large number of ovules per ovary, as a result of shortage of nutrients will be inefficient.
Climatic conditions of the vegetative period also can serve as the reason of low realization of potential efficiency of ovule. High humidity of air and soil leads to the secondary growth, drowning; formation of inflorescences and flowers, that can not form fruit and seeds in time. Rainy and cool weather promotes reduction of summer of pollinators and fast decrease in pollination of bean herbs. Even in favorable weather conditions provision with pollinators corresponds to 5 - 15% from necessary number [3,4]. The difference between number of fertility germinal bags before pollination and unfertilized after pollination reached 46% at alfalfa. Higher provision with pollinators and optimal conditions for pollination would provide essential increase of seed efficiency.
CONCLUSION
The data obtained by us testify that similarity on variability of the characteristics defining seed efficiency of a plant is observed. Similar, hereditarily caused violations of a structure of ovules and germinal bags are met in all studied species of alfalfa that convincingly confirms the law of homological ranks in N. I. Vavilov's hereditary variability which essence consists in that at closely related species ranges of hereditary variability of one specie allow to predict their existence in another.
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