Electron Microscopic Cytochemical Studies on the Glycoproteins in Cellular Membranes of Winter Wheat Seedlings with Concanavalin A-Horseradish Peroxidase Method

The localization and distribution of the glycoproteins in cellular membranes of strong cold hardy winter wheat (Triticum aestivum L. cv. Yanda 1817) seedlings were studied employing the modified cytochemical method using Concanavalin A-Horseradish peroxidase conjugates. The results obtained showed that the reaction products of Horseradish peroxidase activity which indicated the presence of glycoproteins appeared as individual particles distributed at plasmalemma, endoplasmic reticulmn, nuclear envelope and tonoplast in the leaflet cells of the seedlings grown under optimum temperature 25℃ day/20℃ night. After cold acclimation of the seedlings at low temperature during late autumn and early winter, the quantity of glycoproteins distributed in endoplasmic reticulum and nuclear envelope was significantly increased, and glycoproteins were transported into almost all of the plasmodesmata. At some sites of mitochondria and plastides newly formed glycoproteins were observed. However, no distribution of glycoproteins was for,nd in Golgi bodies during the whole observations. The role of glycoproteins for the development and stability of cold resistance in plant through blocking up the plasmodesma passage in the overwintering period of winter wheat seedlings, and the possible differences of the synthetic site and transportation pathway of glycoproteins between animal and plant systems were discussed.     

Growth and cold hardiness of intervarietal hybrids of douglas-fir

Summary Potentials for improvement of the interior variety of Douglas-fir (Pseudotsuga menziesii var. glauca) by hybridization with the coastal variety (P.m. var. menziesii) were explored. The primary objective was to assess possibilities for increasing growth potentials of the interior variety while maintaining adaptation to relatively cold inland environments. Seventy full-sib hybrid families and their half-sib parental lines were grown in two contrasting environments common to the interior variety. Nine traits related to growth, phenology, and freezing tolerance in 4-year-old trees were compared.For traits related to growth (height and diameter) in the inland environment, hybrids equaled the growth of the coastal variety and exceeded the interior variety by 40 percent. For traits related to adaptation (bud burst, bud set, frost damage, tree form, and freezing tolerance), hybrids were intermediate but approached levels characteristic of the interior variety. Survival of hybrids equaled that of the interior variety and was superior to that of the coastal variety.Hybrid characters could not be predicted reliably from those of parental lines. Yet, quantitative genetic analyses suggest that expression of characters related to growth depends on nonadditive genetic effects, but expression of those related to adaptation is somewhat dependent on additive effects.Realization of the tremendous potential of hybridization for improvement of the interior variety will require at least one backcross generation or additional crosses utilizing introgressed populations.     

Hardiness dependent accumulation of phospholipids in leaves of wheat cultivars

Phospholipid content and composition in the leaves of thirteen cultivars of wheat differing in frost hardiness, were compared before and after hardening in order to see whether phospholipids play a role in surviving at low temperatures. The content of phospholipids in the leaves at the end of the hardening could be related to the aquired hardiness, and the relationship between the two phenomena could be described by the regression equation y = (0.174 ± 0.0016) x + 1311. Accumulation of phospholipids represents a hardiness dependent augmentation of membranes. Phosphatidylcholine appeared to be preferentially accumulated in hardy cultivars during the hardening process. As there are no significant differences in phospholipid fatty acid compositions investigated earlier, these results suggest the importance of the polar head group composition of membranes in avoiding frost injury.     

绿化林木氯含量、质膜透性与季节的关系及其抗性的初步研究

研究表明:家榆、糖槭、垂柳和中东杨等四种林木叶片氯含量和质膜透性明显随季节的更替而增加,林木受到氯气污染叶绿素含量显著下降。植物对氯气的吸收能力和抗性并不尽一致,家榆对氯的吸收能力很大,但其抗性居中;中东杨对氯的吸收能力和抗性均居中等;糖槭的吸收能力和抗性均较低;垂柳对氯的吸收能力较大,而且具有很强的抗性。     

Pushed to the limit: consequences of climate change for the Araucariaceae: a relictual rain forest family

Background and Aims

Under predicted climate change scenarios, increased temperatures are likely to predispose trees to leaf and other tissue damage, resulting in plant death and contraction of already narrow distribution ranges in many relictual species. The effects of predicted upward temperatures may be further exacerbated by changes in rainfall patterns and damage caused by frosts on trees that have been insufficiently cold-hardened. The Araucariaceae is a relictual family and the seven species found in Australia have limited natural distributions characterized by low frost intensity and frequency, and warm summer temperatures. The temperature limits for these species were determined in order to help understand how such species will fare in a changing climate.

Methods

Experiments were conducted using samples from representative trees of the Araucariaceae species occurring in Australia, Agathis (A. atropurpurea, A. microstachya and A. robusta), Arauacaria (A. bidwilli, A. cunninghamii and A. heterophylla) and Wollemia nobilis. Samples were collected from plants grown in a common garden environment. Lower and higher temperature limits were determined by subjecting detached winter-hardened leaves to temperatures from 0 to –17 °C and summer-exposed leaves to 25 to 63 °C, then measuring the efficiency of photosystem II (F_v/F_m) and visually rating leaf damage. The exotherm, a sharp rise in temperature indicating the point of ice nucleation within the cells of the leaf, was measured on detached leaves of winter-hardened and summer temperature-exposed leaves.

Key Results

Lower temperature limits (indicated by FT₅₀, the temperature at which PSII efficiency is 50 %, and LT₅₀ the temperature at which 50 % visual leaf damage occurred) were approx. –5·5 to –7·5 °C for A. atropurpurea, A. microstachya and A. heterophylla, approx. –7 to –9 °C for A. robusta, A. bidwillii and A. cunninghamii, and –10·5 to –11 °C for W. nobilis. High temperature damage began at 47·5 °C for W. nobilis, and occurred in the range 48·5–52 °C for A. bidwillii and A. cunninghamii, and in the range 50·5–53·5 °C for A. robusta, A. microstachya and A. heterophylla. Winter-hardened leaves had ice nucleation temperatures of –5·5 °C or lower, with W. nobilis the lowest at –6·8 °C. All species had significantly higher ice nucleation temperatures in summer, with A. atropurpurea and A. heterophylla forming ice in the leaf at temperatures >3 °C higher in summer than in winter. Wollemia nobilis had lower FT₅₀ and LT₅₀ values than its ice nucleation temperature, indicating that the species has a degree of ice tolerance.

Conclusions

While lower temperature limits in the Australian Araucariaceae are generally unlikely to affect their survival in wild populations during normal winters, unseasonal frosts may have devastating effects on tree survival. Extreme high temperatures are not common in the areas of natural occurrence, but upward temperature shifts, in combination with localized radiant heating, may increase the heat experienced within a canopy by at least 10 °C and impact on tree survival, and may contribute to range contraction. Heat stress may explain why many landscape plantings of W. nobilis have failed in hotter areas of Australia.