ФИЗИОЛОГИЯ РАСТЕНИЙ, 2014, том 61, № 3, с. 307-314
ЭКСПЕРИМЕНТАЛЬНЫЕ ^^^^^^^^^^^^ СТАТЬИ
УДК 581.1
PHOTOSYNTHETIC EFFICIENCY AND SURVIVAL of Dactylis glomerata and Lolium perenne FOLLOWING LOW TEMPERATURE STRESS1
© 2014 B. Borawska-JarmuJ-owicz*, G. Mastalerczuk*, M. H. Kalaji**, R. Carpentier***,
S. Pietkiewicz**, S. I. Allakhverdiev****
*Department of Agronomy, Warsaw University of Life Sciences SGGW, Warsaw, Poland **Department of Plant Physiology, Warsaw University of Life Sciences SGGW, Warsaw, Poland ***Groupe de Recherche en Biologie Végétale (GRBV), Université du Québec à Trois-Rivières, Québec, Canada ****K.A. Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Moscow, Russia
Received March 26, 2013
Resistance to low temperature is crucial for overwintering crops. In this work we compared the resistance to low temperature treatment of some varieties of two forage grass species Dactylis glomerata L. and Lolium perenne L. in order to elucidate the reason for the better resistance found in some species. The variety Amila of D. glomerata and Diament of L. perenne were more tolerant to low temperature stress during the emergence and tillering phases as compared to the varieties Amera and Gagat. The improved tolerance and ability for recovery after stress were associated with better recovery of photosynthetic efficiency of these varieties and better survival of their shoots after low temperature stress.
Keywords: Dactylis glomerata - Lolium perenne - chlorophyll fluorescence - low temperature - photosynthesis -photosystem II
DOI: 10.7868/S0015330314030026
INTRODUCTION
For sustainable agricultural grassland in northern countries, there is always a need to develop varieties with better winter survival. For example, Dactylis glomerata L. and Lolium perenne L. are very popular and widely grown forage grasses in Poland. The latter species is already well known to tolerate below-zero temperatures [1, 2]. However, D. glomerata exhibits tolerance to unfavorable environmental conditions, such as drought [3], but its ability to tolerate low temperature, especially during early spring time, seems to be crucial for survival [4].
Nowadays, various physiological parameters are being used as reliable indicators of plant stress tolerance. Photosynthetic efficiency of plants, based on chlorophyll a fluorescence measurements, is one of them [5]. It is a fast, non-destructive, and informative tool for the comparative study of photosynthetic effi-
1 This text was submitted by the authors in English.
Abbreviation'. PSII - photosystem II.
Corresponding authors. Suleyman I. Allakhverdiev and Hazem M. Kalaji. S.I.A., K.A. Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya ul. 35, Moscow, 127276 Russia; fax. +7 (499) 977-8018; e-mail. suleyman.allakh-verdiev@gmail.com; M.H. Kalaji, Department of Plant Physiology, Warsaw University of Life Sciences SGGW, Nowoursynowska 159, 02-776 Warsaw, Poland; e-mail. hazem@kalaji.pl
ciency of control and stressed plants [6]. It helps to get better understanding of the plant responses to environmental condition fluctuations [7, 8]. The development of freezing tolerance is crucial for the survival and productivity of overwintering crops. Hence, it is very important to understand the basis of their tolerance to low temperature conditions [9, 10]. The present investigation aims at elucidating the reasons standing behind the tolerance of some D. glomerata and L. perenne varieties to low temperature stress using their photosynthetic efficiency as the main indicator.
MATERIALS AND METHODS
The experiments were conducted under controlled conditions in plant growth chambers (Phytotron) of Warsaw University of Life Sciences (WULS-SGGW). Fifty seeds of each of Polish forage varieties of Dactylis glomerata L. - Amera and Amila and Lolium perenne L. -Diament and Gagat were sown in pots filled with 3 kg of mineral brown soil of 70% capillary water capacity (optimum moisture content) in five replications. The concentrations of available soil phosphorus (6.6 mg/100 g), potassium (13.3 mg/100 g), and magnesium (6.4 mg/100 g) were medium and the soil pHKCl was 5.1. Fertilization was applied once before sowing (g per pot). N - 1.039, P - 0.268, and K - 0.162. At emergence and tillering
45 40 35 30 25 20 15 10 5 0
-5 | -10 Amera
Dactylis glomerata
5 | -10 Diament
Lolium perenne
LSD
(0.01)
Fig. 1. Leaf greenness index (SPAD units) of D. glomerata (Amila and Amera) and L. perenne (Diament and Gagat) varieties at the tillering phase before (1, control) and after low temperatures (-5°C and -10°C) application (2, immediately; 3, after 48 h).
phases (22 and 43 days after sowing, respectively), plants were exposed for 24 h to either -5°C or -10°C.
Leaf greenness index (relative chlorophyll content) was measured with the SPAD-502 Chlorophyll Meter ("Minolta", Japan) and chlorophyll a fluorescence with the Fluorescence Imaging System -FluorCam800MF ("Photon Systems Instruments", Czech Republic). Measurements were carried out once before (control) and twice after each low temper-
Table 1. ANOVA table results of leaf greenness index (SPAD units) of D. glomerata and L. perenne varieties at the tillering phase treated at low temperatures (-5°C and -10°C) in different time of measure
Factors LSD
Species, A 0.500**
Variety, B 0.851**
Temperature, C 0.496**
Time of measurement, D 0.689**
A x C **
A x D **
B x C **
B x D **
C x D **
A x C x D *
B x C x D *
*P < 0.05; **P < 0.01.
ature treatment (directly and after 48 h). Leaf greenness was measured only during tillering phase, while chlorophyll a fluorescence was measured during both emergence and tillering phases. The chlorophyll fluorescence measurements were done after 30 min of plant dark adaption using light saturation pulse intensity of 3750 ^mol photons/(m2 s) for 800 ms. Subsequently for dark-adapted material, the minimum fluorescence (F0, when all PSII centers are in the open state) and the maximum fluorescence (Fm, when all of them are in the closed state) were measured, and photosystem II (PSII) maximum efficiency (Fv/Fm) was calculated. The amount of survived shoots, dry matter of above-ground mass and roots (g per leaf or shoot depending on the growth phase) after one week from cold stress were also recorded.
All measurements were done in 15 replications on fully developed leaves of randomly selected plants. The experimental data were analyzed by multifactor analysis of variance. The significance of differences between means was determined using the Tukey's test at the significance level P < 0.05 and P < 0.01.
RESULTS AND DISCUSSION
Low temperature causes damage to the plant pho-tosynthetic apparatus [5, 11, 12]. This is mainly due to its influence on both chlorophyll content [13-15] and photosynthetic efficiency [10, 16]. The activity of the enzymes involved in the photosynthetic processes is negatively affected under low temperature stress, thus decreasing the rate of photosynthesis [17]. The chlorophyll content decrease is more expressed due to the fact that membrane-bound chlorophyll is destroyed by
0.9 1
0.8 - 1
0.7 -
0.6 - 3
E*/ 0.5-
^ 0.4 - 2
0.3 -
0.2 -
0.1 -
0
0.19
1
-5 | -10 -5 | -10 -5 | -10 -5 | -10 -5 | -10 -5 | -10 -5 | -10 -5 | -10 |LSD Amera Amila Diament Gagat Amera Amila Diament Gagat
(0.01)
Emergence Tillering
Dactylis glomerata Lolium perenne Dactylis glomerata Lolium perenne
Fig. 2. Maximum quantum efficiency of PSII (F/Fm) of D. glomerata (Amila and Amera) and L. perenne (Diament and Gagat) varieties at emergence and tillering phases before (1, control) and after low temperatures (—5°C and —10°C) application (2, immediately; 3, after 48 h).
1
the free radicals of oxygen despite the protective action of carotenoids [18, 19]. This drop in chlorophyll content has also been associated to metabolic blocks in the porphyrin pathway that leads to the chlorophyll synthesis [20].
The lower leaf chlorophyll contents expressed as leaf greenness (SPAD units) was indeed observed here (fig. 1) during the tillering phase of D. glomerata and L. perenne treated at both -5°C or -10°C. However, highly significant differences in the relative chlorophyll content were observed between the investigated species and varieties of grasses. These differences depended on the low temperature applied, varieties, species, and the time of measurement (table 1).
Low temperatures (-5°C and -10°C) caused significant decreases in the chlorophyll contents of all investigated varieties soon after its application. However, varieties of L. perenne showed the lower relative chlorophyll content values as compared to D. glomerata. The chlorophyll content in both varieties of D. glomerata treated with the lower temperature (-10°C) was reduced stronger (mean 25.1%) than at -5°C treatment (17.0% for Amila and 24.1% for Amera). After 48 h following the end of the freezing period at -5°C, the chlorophyll content significantly increased in Amera and Amila, indicating a recovery from stress. However, these values remained lower than those of the plants grown without temperature stress (control). The plants of L. perenne exhibited a significant decrease in the chlorophyll content immediately after freezing as compared to the control treatment. This decrease was more expressed in plants treated at -10°C independently of varieties (25.7-28.5%). No recovery was observed in 48 h after the end of the freezing treatment, chlorophyll content even dropped further especially after -10°C.
The change in chlorophyll a fluorescence parameters is one the first responses of the plant photosyn-thetic apparatus to any fluctuations in plant growth environment/stress. It thus expresses the actual physi-
Table 2. ANOVA table results of minimal fluorescence (F0), maximal fluorescence (Fm) and maximum quantum efficiency of PSII (Fv/Fm) of D. glomerata and L. perenne varieties at em
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