نوع مقاله : مقاله پژوهشی
نویسنده
دانشیار، موسسه تحقیقات علوم باغبانی، سازمان تحقیقات آموزش و ترویج کشاورزی، کرج، ایران.
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسنده [English]
High temperature has negative effects on olive physiology, especially flowering, fruit growth and oil production. To identify olive cultivars/genotypes tolerant to heat stress, 12 olive cultivars and genotypes with four temperature treatments T1: (34 ± 1.5 ˚C), T2: (37 ± 1.5 ˚C), T3: (40 ± 1.5˚C) and T4: (43 ± 1.5 ˚C) were evaluated at Tarom olive research station, Iran, in 2016. The experiment was conducted as factorial arrangement in randomized complete block design with three replications. The results showed that the photosynthesis rate and water use efficiency decreased with increasing temperature. The results showed that the highest photosynthesis rate was obtained in T1 with 11.84 μmol m-2 s-1 and the lowest in T4 with 4.87 μmol m-2 s-1. In T4 temperature treatment, cv. Manzanilla maintained more than 50% and cv. Amin 44% of their photosynthesis efficiency compared to T1 temperature treatment. The of cultivar temperature × treatment interaction effect showed that the highest photosynthesis rate in T1 was 17.42 and 17.25 μmol.m-2s-1 in cv. Amin and cv. Deira, respectively. At temperatures > 40° C, there was a sharp decrease in the stomatal conductance of the leaves. Cv. Arbequina and Ozine genotype had the highest and lowest water use efficiency with 2.63 and 1.84 mmolCO2 molH2O-1, respectively. Also, the highest water use efficiency was obtained in KH15 genotype and cv. Deira in T1 temperature treatment. Due to the considerable decrease in photosynthesis rate at temperatures above > 40 °C, olive cultivation in areas with hot summers will cause significant reduction in fruit yield and in fruit oil content.
Keywords: Olive, climate change, photosynthesis rate, stomatal conductance, transpiration.
Introduction
One of the problems of olive cultivation that has become more apparent in recent years is climate change particularly rising temperatures. The increase in temperature has caused dramatically decreases in the fruit yield and oil content of olive warm and dry areas of the world. (Siakou et al., 2021) Adaptability of large number of olive cultivars in warm regions require many resources and time (Azimi et al., 2016). However, by examining the factors related to photosynthesis during the peak of summer heat, cultivars with high photosynthesis rate can be screened (Bongi et al., 1987). Then, the selected cultivars can be evaluated for heat tolerance and adaptability to target areas.
The aim of this research was to identify cultivars/genotypes tolerant to heat stress and suitable for regions with warm and dry climatic conditions with high photosynthesis rate under high temperatures.
Materials and Methods
This reseach was carried out to identify olive cultivars/genotypes tolerant to heat stress, 12 olive cultivars and genotypes (Zard, Arbequina, Deira, Amin, Koroneiki, Manzanilla, Meshkat, Zagros and genotypes of Ozineh, Gorgan3, Tmn2, Kh15) with four temperature treatments T1: (34 ± 1.5 ˚C), T2: (37 ± 1.5 ˚C), T3: (40 ± 1.5˚C) and T4: (43 ± 1.5 ˚C) were evaluated at Tarom olive research station, Iran, in 2016. The experiment was conducted as factorial arrangement in randomized complete block design with three replications. Physiological indices were measured using the LCI model of UK-ABC. Photosynthesis related indices were measured in three replications, and in each replication at least on three leaves from completely developed leaves of the current year for each cultivar/genotype. The measured indices included: difference of reference CO2 and atmospheric CO2 concentration with CO2 of the sub-stomatal chamber, photosynthetic active radiation (P. A. R.), chamber temperature, leaf temperature, stomatal conductance (gs), transpiration (E), photosynthesis rate (A), water use efficiency (WUE), which was calculated from the A/E ratio (Bongi et al., 1987). The mean leaf temperature was 0.81 ◦C higher than the ambient temperature, during the implementation of the experiment. The average atmospheric CO2 concentration was 388 ppm. The minimum, maximum and mean of P. A. R was 1547, 1880 and 1721 μmol m-2 s-1, respectively. Analysis of variance was performed using Minitab version 17 software, and means were compared using Tukey's test at the 5% probability level.
Results and Discussion
Analysis variance showed that the effect of cultivar, temperature and genotype × temperature treatment interaction effect on photosynthesis rate (A) were significant at the 5% level. Means comparison revealed that cv. Amin had the highest mean photosynthesis rate with 12.14 μmol m-2s-1. There was no significant difference between cv. Amin, cv. Deira, cv. Zagros and cv. Manzanilla for photosynthesis rate. The lowest (A) was obtained in cv. Zard and Ozine genotype with 6.97 and 6.13 μmol m-2 s-1, respectively. The interaction effect of genotype × temperature on (A) indicated that lowest (A) was obtained in cv. Meshkat and cv. Koroneiki in T4 with 3.03 and 3.15 μmol m-2 s-1, respectively. The photosynthesis rate of olive leaves usually does not exceed 18 μmol m-2s-1at light intensity of 1900 μmol m-2 s-1 (Bongi et al., 1987).
The mean comparison effect showed that the highest stomatal conductance (gs) was related to cv. Amin with 0.239 molCO2 m-2 s-1, and the lowest was related to Ozine genotype with 0.091 molCO2 m-2 s-1. Cv. Deira and cv. Manzanilla had similar stomatal conductance with 0.185 molCO2 m-2 s-1. The stomatal conductance in cv. Koroneiki was 0.131 molCO2 m-2 s-1 and Ozine genotype with 0.091 molCO2 m-2 s-1 had the lowest (gs). Siakou et al. (2021) reported that the stomatal conductance in cv. Koroneiki was between 0.65-0.228 molCO2 m-2 s-1. As the temperature increased, the stomatal conductance decreased. In T4, the stomata conductance was 0.064 molCO2 m-2 s-1 which decreased by 69.8% as compared to T2 temperature treatment. There was linear relationship between photosynthesis rate and stomatal conductance with coefficient of determination of R2 = 0.7873.
Cultivar Arbequina with 63.2 mmolCO2 molH2O-1 had the highest water use efficiency and the lowest water use efficiency belonged to cv. Koroneiki and Ozine genotype with 1.89 and 1.84 mmolCO2 molH2O-1, respectively. Water use efficiency had a direct relationship with (A) and a negative relationship with transpiration (E) (Chartzoulakis et al., 199b). The lowest water use efficiency for all cultivars/genotypes was in T4 in, except in cv. Zard. The lowest water use efficiency belonged to Ozine genotype in T4 with 0.99 mmolCo2 molH2O. The mean comparison indicated that the cv. Amin had the highest transpiration with 5.84 mmolH2O m-2 s-1 and cv. Zard the lowest with 3.11 mmolH2O m-2 s-1, and other genotypes had no significant differences. With increasing temperature, leaf transpiration increased but decreased in T4. The reduction of (E) at temperature > 43°C was due to the closing of the stomata.
References
Azimi, M., Arji, I., Zeinanloo, A.A., Taslimpor, M.R. and Ramazani, M. 2016. Evaluation of adaptability of some olive (O. europaea L.) cultivars in different climates of Iran. Journal of Seed and plant, 1-32(3), pp.275-292 (in Persian). DOI: 10.22092/SPIJ.2016.112605
Bongi, G. Mencuccini, M. and Fontanazza, G. 1987. Photosynthesis of olive leaves: effect of light flux density, leaf age, temperature, peltates, and H2O vapor pressure deficit on gas exchange. Journal of the American Society for Horticultural Science, 112(1), pp.143-148. DOI: 10.21273/JASHS.112.1.143
Chartzoulakis, K., Michelakis, N. and Stefanoudaki, E. 1999b. Water use, growth, yield and fruit quality of "Bonanza" oranges under different soil water regimes. Advances in Horticultural Science, 13(1), pp.6-11.
Siakou, M., Bruggeman, A., Eliades, M., Zoumides, C., Djuma, H., Kyriacou, M.C., Emmanouilidou, M.G., Spyros, A., Manolopoulou, E. and Moriana, A. 2021. Effects of deficit irrigation on 'Koroneiki' olive tree growth, physiology and olive oil quality at different harvest dates. Agricultural Water Management, 258. DOI: 10.1016/j.agwat.107200
کلیدواژهها [English]
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