Yasemin Ekmekçi

Changes in the electrophoretic pattern of soluble shoot proteins of wild and cultivated tetraploid wheats following cold acclimation and freezing

The tolerance of tetraploid wild wheat Aegilops L. (Ae. biuncialis; Ae. cylindrica) species and cultivated wheat Triticum durum L. (cv. Firat-93; Harran-95) cultivars grown in Turkey to freezing was investigated by regrowth experiments and cold and freezing protein analyses. The results of the regrowth experiment showed that the seedling shoot length of genotypes decreased significantly when the duration of freezing time was increased from 3 to 24 h, compared to the untreated seedling at the end of the regrowth period, but increased when the regrowth period was increased from 24 to 72 h, at -5 ′ 1 °C. At -7 ′ 1 °C, none of the genotypes survived after 6, 12, and 24 h freezing periods, but did survive after 3 h. Although all the genotypes showed a tolerance greater than 50% at -5 ′ 1 °C for 3 h, wild wheats were found to be more tolerant than the cultivated wheats. On the other hand, during -7 ′ 1 °C freezing treatments, only Ae. biuncialis was tolerant for 3 h, while the other genotypes were sensitive to all the periods. The results of electrophoretic patterns of soluble shoot proteins showed that cold acclimation and cold acclimation plus freezing conditions induced two separate groups of proteins. In the first group, only one protein (67 kDa pI 5.7) was induced in both genotypes. This protein may not be associated with development of freezing and may have resulted from growth at low temperature. In the second group, new proteins were synthesized in tolerant Ae. biuncialis (66-22 kDa pI 7.5-5.5) in higher amounts than in sensitive Harran-95 (66-42 kDa pI 7.3-5.7). The proteins newly synthesized under these conditions may be associated with the cold resistance capacity of such genotypes. Also, a 50 kDa pI 6.4 protein was induced in the tolerant genotype. These proteins may play an important role in cellular adaptation to freezing.

Variation of total soluble seminal root proteins of tetraploid wild and cultivated wheat induced at cold acclimation and freezing

The relationship between total soluble seminal root proteins induced at cold acclimation and freezing tolerance in tetraploid wild wheat Aegilops L. (Ae. biuncialis, Ae. cylindrica) and cultivated wheat Triticum turgitum L. (Firat-93, Harran-95) was investigated. Cold acclimation was performed at 0 °C for 7 days. Freezing tolerance was determined with survived roots after freezing treatments at −5 and/or −7 °C for 3, 6, 12 and 24 h. At −5°C, all tetraploid genotypes showed over 60% tolerance for 3 h. This effect was also present in wild wheat for 6 h, but was decreased in cultivated wheat to 30–35% tolerance for 6 h. Only Ae. biuncialis was able to show 52% tolerance just for 3 h freezing period at −7 °C. However, all the genotypes were not survived at −7 °C, for 6, 12 and 24 h. Cold acclimation induced greater amounts of new soluble seminal root proteins in tolerant Ae. biuncialis (29–104 kDa, pI 5.4–7.4) than in sensitive Harran-95 (29–66 kDa, pI 6.1–8.3). Synthesis and accumulation of these proteins may be related to degree of freezing tolerance of these genotypes.

Antioxidant response and photosynthetic characteristics of Xerophyta viscosa Baker and Digitaria sanguinalis L. leaves induced by high light

The effects of high light (1500 mmol m-2 s-1) on photosynthetic characteristics and antioxidant enzyme capacity of the monocotyledonous resurrection plant Xerophyta viscosa Baker and the crab grass Digitaria sanguinalis L. were investigated as a function of time for 20 days of treatment. High light treatment caused photoinhibition in D. sanguinalis, whereas X. viscosa was less affected. The reduction in photochemical efficiency of PSII in X. viscosa during high light probably contributed to the decline in the photosynthesis rate, since other factors such as intercellular CO2 concentration, chlorophyll a + b, and carotenoid content were not markedly changed. On the other hand, the net photosynthesis rate of D. sanguinalis declined considerably during the high light treatment, probably, in part, due to the decline in photochemical efficiency of PSII. The increase in the transpiration rate corresponded to an increase in stomatal conductance in both species. Long-term high light brought about photosynthetic pigment chlorophyll (a + b) loss and membrane leakage in D. sanguinalis only. While concentration of anthocyanin increased in both species, carotenoid increased only in D. sanguinalis. High light caused significant activation of all superoxide dismutase (SOD) isoenzymes, especially Cu/ZnSOD, in both species. However, total SOD activity of X. viscosa was significantly greater than D. sanguinalis during the high light treatment. The total peroxidase and glutathione reductase activity and isoenzyme amounts of D. sanguinalis were significantly higher than those of X. viscosa, and levels increased in the former only during high light treatment.

Freezing tolerance of chickpea: biochemical and molecular changes at vegetative stage

The aim of this study was to find a correlation between the freezing tolerance of three chickpea (Cicer arietinum L.) cultivars (İnci, Işık-05, and Sarı-98) and their wild relative C. echinospermum and physiological responses. Chickpea plants (15-d-old) were subjected to cold acclimation (CA) (10 °C for 7 d), freezing (-3 or -5 °C for 2 h), and subsequent rewarming (25 °C for 7 d). In two separate experiments with three replications, we determined growth, water status, photosystem 2 photochemical activity, photosynthetic pigments, H2O2, malondialdehyde, and proline content, relative leakage ratio, antioxidant enzyme activities, and gene expressions in cultivars different in freezing tolerance. Freezing temperatures adversely affected all the physiological parameters of all cultivars. Rewarming did not lead to complete recovery. The cultivar İnci was more tolerant to the freezing temperatures than others.

Morphological and physiological responses to drought stress of European provenances of Scots pine

Increased frequency and intensity of drought episodes as a consequence of current and predicted climatic changes require an understanding of the intra-specific variability in structural and physiological characteristics of forest trees. Adaptive plasticity and genotypic variability are considered two of the main processes by which trees can either be selected or can acclimate to changing conditions. We tested for the relative importance of genotypic variability, phenotypic plasticity and their interaction by comparing the growth and physiological performance of 15 provenances of Scots pine (Pinus sylvestris L.), under two contrasting irrigation regimes. Selected provenances representing the distribution range of the species in Anatolia, Turkey, were contrasted with seed sources spanning the range from Spain to the UK, in Europe. We found a strong latitudinal differentiation among the 15 provenances for survival after drought, largely the result of the higher mortality of some western and central European provenances. Differentiation in diameter and height growth was also clear with the worst provenance coming from Western Europe (UK). Among the Turkish provenances, the more extreme southern high-elevation populations showed greater survival and lower growth rates overall. Differences in growth and survival were related to differences in photosynthetic pigment and nutrient contents and in the photosynthetic efficiency of photosystem II. Plasticity was strongest for growth characters and pigment contents.