Candidate Agr. Sci.
Klemeshova K.V., Pashchenko O.I.
The State Research Institution
All–Russian Scientific and Research Institute of Floriculture and Subtropical
Crops of the
Russian Academy of Agricultural Sciences, c.
Sochi, Russia
Diagnostics of Freesia
functional state on the Black Sea coast of Krasnodar region
The
paper discusses some characteristics of Freesia
refracta Klatt pigment system and the possibilities of using this parameter
as a diagnostic feature of plant resistance in limiting environmental
conditions. The study included the following cultivars and new hybrids of
freesia from the selection of All–Russian
Scientific and Research Institute of Floriculture and Subtropical Crops, having different flowering terms: Georgy Pobedonosets, Melange,
I-108-1, P-28-1. The paper considers possible applying of optical techniques
used for the assessment of plants functional state, based on the use of the
parameters of a slow chlorophyll fluorescence induction.
Key words:
freesia, cultivar, hybrid form, pigment system, slow induction of chlorophyll,
correlation.
INTRODUCTION
Freesia (Freesia Klatt, fam. Iridaceae) – is one of the most common cut flower crops grown in protected
grounds. Freesia was introduced to Russia in early 1970s, and in 1980s it was developed
on an industrial scale. Thanks to its rich colour, fragrance of flowers and
exquisite shape this culture is becoming increasingly popular in Russia. The
possibilities of obtaining cut products throughout the year, and particularly
during the winter and early spring, make its cultivation highly profitable.
There is a growing demand on planting materials from farmers, especially in the
south of the Kuban.
In the
autumn-winter-spring, freesia is usually cultivated in a greenhouse heated to
maintain the optimum temperature (depending on the stage of plant development
from 8–10 to 18–20 ° C). The area of the Black Sea coast of Krasnodar region is
one of the few in Russia where the work is carried out with vegetative plants
under unheated glass greenhouses. In winter and early spring, air temperatures
in such a greenhouse can be from 0 to –5 ° C in some days, while in the second
half of April and May, it may rise up to 25–30 ° C. Extreme growing conditions
adversely affect the physiological state of the plants themselves, thus causing
changes in terms and duration of flowering, as well as bad quality of the cut material
[3]. Currently, remain unexplored the problems of freesia cvs resistance in an
unheated closed ground by some physiological parameters.
One of the most
important indicators of plant adaptive capacity in limiting conditions is an
efficiency of the photosynthetic apparatus due to the pigment system which is
extremely sensitive to adverse environmental factors. This is what allows us to
use changes in pigment system caused by various stressors as a diagnostic feature
[2].
SUBJECTS
AND METHODS
The
study included freesia cvs (Freesia
refracta Klatt) and new hybrid forms from the selection of All–Russian Scientific and Research Institute of Floriculture
and Subtropical Crops, having different
flowering terms.
Georgy Pobedonosets
(control) is a cv of a late flowering period, selection year is 1998. Plant
height – 96,2 cm, there are 3 peduncles on one plant, about 9–10 flowers in the
inflorescence, the flowers are very large, flower height is 7,6 cm, diameter is
6,5 cm, petal colour is red, flower type is undouble. This cv is stable in a culture.
Melange is a cv of an average
flowering period, resistance in the culture is very good, selection year is 2002.
Plant height is 81,0 cm, the number of stems is from 4 to 5, flower height is
7,2 cm, flower diameter – 7,5 cm, flower colour is light-lilac, throat of the
flower is light yellow, stains – yellow. Number of flowers per inflorescence is
from 11 to 12.
Hybrid Form I-108-1 has a very early flowering
period, selection year is 2001, peduncle height is 32,0 cm, inflorescence
length is 10,0 cm, base colour of a flower is white, throat is white-cream, stains
are yellow, flower diameter is 5,8 cm, flower height – 7,2 cm, number of
flowers in the inflorescence is from 7 to 9.
P-28-1 is a hybrid form
of an average flowering period, selection year is 2008. Peduncle height is 33,0
cm, inflorescence length is 7,0 cm, the main colour is blue and purple, throat color
is white, without strains, flower diameter is 7,0 cm, flower height – 7,4 cm,
number of flowers per inflorescence is 9 or 10.
The pigment
content was determined in an extract of green leaves on 100% acetone by the
method of A. Shlyk, using computational formulas of Ziegler and Egle [6].
The parameters of
the slow chlorophyll fluorescence induction (SCFI) were determined on the
device LPT-3C, by the method of plants functional state [1].
RESULTS AND
DISCUSSION
Characterization
of pigment apparatus in leaves of different freesia cvs is shown in table 1.
Table 1
Characteristics on pigment
apparatus in freesia leaves of different cvs
|
Sample |
Са, mg/g |
Сb,
mg/g |
Σchlor.,
mg/g |
Σcarot.,
mg/g |
Са/Сb |
Σchlor./
Σcarot. |
|
I-108-1 |
1,208±0,02 |
0,527±0,07 |
1,807±0,05 |
0,834±0,04 |
2,648±0,05 |
2,169±0,03 |
|
P-28-1 |
1,321±0,04 |
0,532±0,02 |
1,853±0,05 |
0,851±0,02
|
2,485±0,02 |
2,178±0,02 |
|
Melange |
1,155±0,01 |
0,438±0,01 |
1,593±0,02 |
0,734±0,01 |
2,640±0,05 |
2,170±0,01 |
|
Georgy Pobedonosets |
1,188±0,02 |
0,468±0,01 |
1,656±0,03 |
0,778±0,02 |
2,539±0,01 |
2,129±0,01 |
|
LSD05 |
0,05 |
0,07 |
0,08 |
0,04 |
0,06 |
0,04 |
The main
photosynthetic pigment in freesia leaves is chlorophyll a, its content varies
from 1,155 mg/g (cv Melange) to 1,321 mg/g (hybrid form P-28-1). The content of
chlorophyll b, indicating the adaptation level of plants to low light, is on
average 0,491 mg/g among cvs. While the highest content of chlorophyll b was
observed in hybrid forms I-108-1 (0,527 ± 0,07 mg/g) and P-28-1 (0,532 ± 0,02
mg/g) which significantly exceeds the amount of this pigment group in cv
Melange (LSD05 = 0,07). It should be noted that the high content of
chlorophyll b in plants is preferable for photosynthetic activity, especially
in dense plantation.
It is not only
the content of certain pigments important in the study of pigment complex, but also
their correlation, for instance we can judge shade tolerance by the ratio of
chlorophyll a to chlorophyll b. When there is a large lack of light,
chlorophyll content becomes significantly less than in normal lighting
conditions. During the growing season there is a self-shadowing of the biggest
part of freesia leaves due to the cultivation conditions. The highest ratio of
chlorophylls (a/b) was observed in the hybrid form I-108-1 (2,648 ± 0,05) and cv
Melange (2,640 ± 0,05), the ratio of the smallest was in hybrid form P-28-1
(2,485 ± 0 02), and these differences are significant (LSD05 = 0,06).
Carotenoids
perform photoprotective function in plant defense reactions (they protect the
reaction centre from powerful energy flows at high light intensities and
stabilize the lipid phase of the thylakoid membranes, protecting it from
peroxidation), therefore, the high content of carotenoids in plants is
preferable to stimulate adaptive responses and reduce overall stress in plants
[4]. The hybrid forms presented in the study significantly differ from the cvs in
the content of carotenoids (LSD05 = 0,04), for example, carotenoid
content in hybrid forms made up 0,843 mg/g, and in cvs it was 0,756 mg/g.
The ratio of chlorophyll
amount to carotenoids is the most informative feature as it indicates not only
the degree of plants adaptation to light, but also to adverse conditions. The
lower the ratio is, the higher plant resistance is. The minimum value of the
ratio of chlorophyll to carotenoids was observed in the control cv Georgy
Pobedonosets (2,129 ± 0,01), in the rest samples this parameter had
approximately equal values (from 2,169 ± 0,03 to 2,178 ± 0,02).
The main reason
for the decline of quality of cut flower material of the cultivated plants is
their low resistance to some stress factors. It is important to identify the
main factors that could characterize plant resistance to environmental stress.
The solution to this problem is possible only on the basis of improving the
known methods and developing new techniques of functional diagnosis and
identifying criteria. The aim of this is to assess their adaptive capacity,
based on the use of these stable features associated with basic physiological
functions such as the content of pigments and others.
To carry out a
large number of comparative measurements which concern evaluation of plant functional
state and need to take place in a limited time, optical methods of rapid
diagnosis have been developed in Russia. They have been tested in a number of
research centres – in Rhyne University (Germany), Russian Research Institute of
Genetics and Selection of Fruit Plants, in the All-Russian Research Institute
of Horticulture (c. Michurinsk) and All–Russian
Scientific and Research Institute of Floriculture and Subtropical Crops (c. Sochi) and demonstrated their suitability to solve wide range of
scientific and practical problems.
More than 80% of
the optical methods used to assess plant functional state are based on applying
chlorophyll fluorescence induction. Chlorophyll fluorescence induction has a
close connection with the integral processes of photosynthesis, and depends on
light and water regime, temperature, etc. Due to the high information content
and versatility of the method, as well high speed of analysis, non-destructive
nature of the measurements and no labor-intensive operations,
chlorophyll-fluorescence has been successfully used in the study of the
reaction of the photosynthetic apparatus to various abiotic effects [1, 5].
The parameters of
the slow chlorophyll fluorescence induction in freesia leaves are shown in table
2.
Table 2
Parameters of the slow chlorophyll
fluorescence induction
in freesia leaves of
different cvs
|
Sample |
Fm/Ft |
Kf_T |
Kf_n |
|
I-108-1 |
2,156±0,48 |
0,517±0,11 |
0,405±0,07 |
|
P-28-1 |
2,062±0,09 |
0,514±0,02 |
0,386±0,02 |
|
Melange |
2,028±0,26 |
0,499±0,07 |
0,381±0,04 |
|
Georgy Pobedonosets |
1,508±0,35 |
0,308±0,15 |
0,238±0,10 |
|
LSD05 |
0,44 |
0,13 |
0,09 |
Sustainability
index (Fm/Ft) is calculated as the ratio of the maximum fluorescence to a
steady level, and has no dimension and no varietal or species specificity.
Normally, the Fm/Ft has a value from 2 to 4, and is rarely more than 4 units.
The minimum value of viability index has been observed in cv Georgy
Pobedonosets (control), and is 1,508 ± 0,35, which is significantly lower than in
other cvs (LSD05 = 0,44).
The coefficient
of photosynthetic activity (Kf_n) reflects the efficiency of light utilization
in photosynthesis; it also has no dimension and does not depend on the species or
varietal identity. Normally, the value of the coefficient of photosynthetic
activity is 0,6 and above, under the influence of various stressors it decreases
proportionally to the weakening of a photosynthetic function. This indicator does
not exceed 0,6 in all the samples, and ranges from 0,238 ± 0,10 in the cv
Georgy Pobedonosets till 0,405 ± 0,07 in the hybrid sample I-108-1, which can
be associated with pathological processes caused by stress factors.
In practice, it
is advisable to use other parameters of the slow chlorophyll fluorescence
induction. Thus, the estimated coefficient of photosynthetic activity (Kf_T),
identical in meaning to the parameter Kf_n, is determined by the calculated
steady-state level of fluorescence for 30 ... 60 seconds of SCFI subscription (slow
chlorophyll fluorescence induction). In practice, the higher the indicator is,
the better the functional state of the plant body is. In the researched samples
the minimum value of this parameter was observed in the control cv Georgy
Pobedonosets (0,308 ± 0,15), and the calculated coefficient of photosynthetic
activity is significantly higher in the rest of the samples, ranging from 0,499
± 0,07 (cv Melange) till 0,517 ± 0,11 (hybrid form I-108-1). However, this indicator
is somewhat artificial in nature and its use is justified in cases where it is
necessary to conduct numerous comparative measurements at a limited time.
On the basis of
the data obtained we have counted the pair correlation coefficients between the
main characteristics of the pigment apparatus and the parameters of the slow chlorophyll
fluorescence induction in freesia leaves of different cvs (Table 3).
Table 3
Pair correlation
coefficients between the characteristics of the pigment
apparatus and the SCFI
parameters in freesia leaves of different cvs
|
Total correlation |
Fm/Fт |
Kf_T |
Kf_n |
|
Σchlorophylls, mg/g |
0,48 |
0,45 |
0,45 |
|
Σcarotenoids, mg/g |
0,37 |
0,34 |
0,33 |
|
Са/Сb |
0,37 |
0,30 |
0,37 |
|
Σchloroph./ Σcarot. |
0,95 |
0,98 |
0,96 |
Preliminary
correlation analysis has shown the presence of a high dependence between the
ratio of chlorophylls amount to the total carotenoids and SCFI parameters, but
at this research stage it is early to draw any conclusions, as complete and
valid conclusions can be made only after longer studies.
CONCLUSION
Based on the preliminary
data, we can make positive conclusions about the possibility of using specific features
of the pigment system in freesia leaves, as a diagnostic feature of plant
resistance to the limiting environmental conditions. The dependences recorded
between the optical techniques and structural features of the pigment system
will allow us to develop a rapid diagnosis of freesia functional state on the
Black Sea coast of Krasnodar region.
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