Research Article |
Corresponding author: IT Kishchenko ( ivanki@karelia.ru ) Academic editor: Yuliya V. Bespalaya
© 2019 IT Kishchenko, MA Tikhova.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Kishchenko IT, Tikhova MA (2019) Morphology and viability of pollen grains of Picea L. species in the conditions of introduction. Arctic Environmental Research 19(2): 75-80. https://doi.org/10.3897/issn2541-8416.2019.19.2.75
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Research was carried out in the Botanical garden of Petrozavodsk state University, located on the Northern shore of the Petrozavodsk Bay of lake Onega (middle taiga subzone, 61°47’ n). during two vegetation periods. The objects of study served as an indigenous species Picea abies (L.) Karst, and two introduced species – Picea pungens Engelm. f. glauca Regel. Picea canadensis (Mill.) Britton et al. Age and height of Picea abies – respectively 47 years and 16 m, Picea pungens – 36 years and 12 m, Picea canadensis – 22 years and 6 m. Morphological characteristics of pollen grains were estimated by the following morphometric characteristics: diameter, length of pollen grain, polar axis, height of pollen grain with air bags, area of pollen grain projection, perimeter, form factor and eccentricity. The study of statistical characteristics of samples allowed us to establish that the accuracy rate in determining the arithmetic mean values of the morphometric parameters under study is quite high and varies by species from 0.7 to 3.5%.The pollen grains of the studied species were found to be bag-shaped or wide-ellipsoid. Their outline from the pole is elliptical, from the equator it is wide-trapezoid. The colour of the grains is yellow, the surface of the body is lumpy, and the bags are rough. The pollen grains of the aboriginal Picea abies species are 3–20 % larger than those of the introduced species. The size of the Picea pungens pollen exceeds that of Picea canadensis by 4–48 %. There is a fairly strong linear relationship between individual morphometric parameters of a pollen grain (r = 0.5–0.8). The viability of the pollen of the aboriginal Picea abies species in South Karelia is about twice as high as that of the introduced species of Picea canadensis and Picea pungens.
introduction, spruce, pollen, morphology, viability
The study of the introduced plants resistance to new conditions cannot be limited to observations of external morphological changes occuring in the process of growth and development. It is necessary to clarify the characteristics and internal changes in the vegetative and generative buds, as well as in the strobile. It is on the characteristics of all developmental stages of generative organs and the degree of male and female gametophytes formation that the quantity and quality of seed production depend (
Pollen viability and the morphology of pollen grains in Karelia were previously studied for Pinus sylvestris L. (
The comparative study of pollen grains viability and morphology of two introduced species and a local species of Picea abies was carried out with the aim of determining the reproductive potential of the introduced species.
The studies were carried out at the Botanical Gardens of Petrozavodsk State University located on the north shore of the Petrozavodsk Bay of Lake Onega (central taiga subzone, 61°47’N) during two vegetative periods. The type of soil is humus-ferruginous-illuvial podzol (pH 4.7).
The subjects of the studies were the aboriginal species of Picea abies (L.) Karst and two introduced plants of Picea pungens Engelm. f. glauca regel. and Picea canadensis (Mill.) Britton et al. The age and height of P. abies is 47 years and 16 m, the P. pungens is 36 years and 12 m, the P. canadensis is 22 years and 6 m.
The viability of pollen grains was determined on fresh and fixed material. Fresh pollen was germinated on distilled water and on 20 % sucrose solution (in three replications). The calculation of fertile and sterile grains and the study of the growth characteristics of pollen tubes were carried out on the 5th day by a light microscope.
The pollen was fixed according to Chamberlain (
The measurement results were processed by variation statistics methods (
The vital potential of pollen grains of one or several closely related species can be indirectly estimated by their size: the larger they are, the more vigorous the germination is. The morphological characteristics of pollen grains were assessed according to the following morphometric characteristics: diameter, pollen grain length, polar axis, height of a pollen grain with air bags, pollen grain projection area, perimeter, form factor, and eccentricity (
Species | Arithmetic mean value error, μm | Measure of the accuracy of experience,% | Standard deviation, μm | Coefficient of variation,% |
---|---|---|---|---|
The Equatorial diameter | ||||
Picea abies | 47.2±0.52 | 2.5 | 5.22 | 11.0 |
P. pungens | 45.7±0.40 | 8.7 | 3.96 | 8.8 |
P. canadensis | 44.0±0.29 | 6.7 | 2.88 | 6.4 |
Length | ||||
P. abies | 35.8±0.49 | 1.4 | 4.86 | 13.8 |
P. pungens | 32.6±0.41 | 1.3 | 4.14 | 12.7 |
P. canadensis | 27.9±0.22 | 0.8 | 2.16 | 7.5 |
The polar axis | ||||
P. abies | 30.1±0.40 | 1.3 | 3.96 | 13.3 |
P. pungens | 26.8±0.38 | 1.4 | 3.78 | 13.9 |
P. canadensis | 25.0±0.29 | 1.2 | 2.88 | 11.4 |
The body height with the air bags | ||||
P. abies | 36.9±0.36 | 1.0 | 3.60 | 9.8 |
P. pungens | 33.0±0.36 | 1.1 | 3.58 | 10.8 |
P. canadensis | 29.8±0.62 | 2.3 | 2.52 | 8.1 |
The area of the projection | ||||
P. abies | 1840±60.1 | 3.5 | 0.63 | 18.9 |
P. pungens | 1489±70.3 | 4.6 | 0.56 | 20.8 |
P. canadensis | 1312±10.2 | 0.8 | 0.29 | 13.6 |
The perimeter of the projection | ||||
P. abies | 168±4.3 | 2.4 | 0.35 | 9.6 |
P. pungens | 157±4.3 | 2.3 | 0.35 | 10.6 |
P. canadensis | 106±0.8 | 7.3 | 0.81 | 21.7 |
Formfactor | ||||
P. abies | 16.2±0.01 | 0.6 | 0.08 | 2.0 |
P. pungens | 16.6±0.01 | 0.6 | 0.18 | 2.1 |
P. canadensis | 8.6±0.05 | 5.9 | 0.49 | 12.1 |
The eccentricity | ||||
P. abies | 0.64±0.02 | 2.5 | 0.17 | 20.0 |
P. pungens | 0.59±0.01 | 1.4 | 0.13 | 14.9 |
P. canadensis | 0.57±0.01 | 1.1 | 0.12 | 13.2 |
The pollen grains of the Picea species have the same bag-shaped or wide-ellipsoid shape. Their outlines from the pole are elliptical, and from the equator they are wide-trapezoid, sometimes almost triangular (Figure
Microscopy of pollen grains (body and air bags, ×360). Picea abies (1), P. canadensis (2), P. pungens (3)
The variants distribution in samples of all morphological parameters corresponds to the normal distribution law. The study of the statistical characteristics of the samples made it possible to establish that the accuracy rate in determining the arithmetic mean values of the morphometric parameters under study is quite high and varies by species from 0.7 to 3.5 % (Table
The highest variability is noted for such indicators as the area of pollen grain projection and eccentricity. Their variation coefficients vary within 15–21 %, as for the other indicators they are lower and sometimes significantly lower (2–6 %). The trend towards a decrease in variability of linear indicators of pollen grains from P. abies to P. pungens and P. canadensis is clearly expressed.
P. abies was found to have the largest values of the studied signs of a pollen grain. Its equatorial diameter in P. abies (47.2 μm) is 3.2 and 7.3 % bigger than in P. pungens and P. canadensis. According to T.P.
The body length of pollen grains of P. abies is longer than that of P. pungens and P. canadensis by 10.2 and 28.3 %, the polar axis – by 11.9 and 20.0 %, the height of a pollen grain with air bags – by 11.2 and 23.5 %, the area of pollen grains – by 16.8 and 32.8 %, the value of the perimeter of the projection of pollen grain – by 7.0 and 58.5 % respectively. Thus, the aboriginal species has the largest pollen grain body, which indirectly proves the highest nutrient content contributing to the efficient growth of the pollen tube and fertilization. Significantly larger sizes of pollen grains of the aboriginal species (P. obovata) as compared with the introduced species (P. pungngens) were previously discovered by Е.V. Bazhina and M.I. Sedaeva (2017).
The pollen grain form factor (the perimeter squared in relation to the pollen grain area) is statistically the same in Picea abies and Picea pungens (16.2 and 16.6), but approximately 90 % more than that in Picea canadensis.
A comparison of the morphological characteristics of the pollen grain of P. pungens and Picea canadensis showed that the equatorial diameter of the pollen grain of P. pungens is larger than that of P. canadensis by 3.9 %, the body length – by 16.8 %, the polar axis – by 7.2 %, the body height – by 11.1 %, the area – by 13.7, and the perimeter – by 48.1 %. The increase in the size of the P. pungens pollen grains as compared with P. canadensis was also found by E.V. Bazhina and M.I. Sedaeva (2017).
A correlation analysis was performed to clarify the nature and the strength of the relationship between the studied morphometric characteristics of the pollen grain. A linear relationship of different strength was found between some of the studied signs (Table
Correlation coefficient between morphometric signs pollen grains of various species of Picea*
Morphometric feature | Plant species | ||||||||
Picea abies | P. pungens | P. canadensis | |||||||
А | В | D | А | В | D | А | В | D | |
Е | 0.54 | 0.22 | 0.22 | – | 0.53 | 0.52 | – | 0.30 | 0.31 |
А | – | 0.23 | 0.24 | 0.30 | 0.22 | 0.20 | 0.31 | 0.0 | 0.0 |
В | – | – | 0.72 | – | – | 0.81 | – | – | 0.71 |
The studies showed that the pollen tubes of the plants grown on sucrose-bearing medium appear as early as on the 1st day, and on water – only on the 2nd or even the 3rd day. During pollen germination starch grains occupy most of its volume. At the same time, there are far more of them on sucrose than on water. Pollen tubes on sucrose are 2−3 times longer than those germinated on water.
The incubation medium also has a significant effect on pollen viability. This indicator for the aboriginal species germinated on sucrose-bearing medium is 21 % higher than those germinated on water, whereas for the introduced species – by 30–33 %. Similar results were previously obtained by I.A. Smirnov (1977). The viability of P. abies pollen is on average twice as high as that of the introduced species. The differences in this indicator between the latter do not exceed 8 %. The pollen viability of P. abies germinated on water was found to be 80 %, 97 % – on sucrose-bearing medium; of P. pungens – 40–45 %, of P. canadensis – 50–60 %. It should be noted that in the homeland of the introduced species (North America) this indicator reaches 90 %. The low viability of these species pollen appears to be related to the adverse ecological conditions of the introduction area (
The study was supported by the Russian Foundation for Basic Research (project 18-44-100002 p_a).