quality associated with chilling tolerance is important. During chilling stress, the functionality and survival of a plant cell depends on the integrity of membranes. The chloroplast is typically the first location within the cell to incur CI ( Kimball and
Charles Fontanier, Justin Quetone Moss, Lakshmy Gopinath, Carla Goad, Kemin Su, and Yanqi Wu
Zhengrong Hu, Erick Amombo, Margaret Mukami Gitau, Aoyue Bi, Huihui Zhu, Liang Zhang, Liang Chen, and Jinmin Fu
temperature is considered as a key environmental factor limiting bermudagrass growth and utility ( Fan et al., 2014 ). However, limited research has been done on chilling resistance in bermudagrass. Therefore, detailed information about chilling stress
Fang Yu, Zhiming Ni, Xingfeng Shao, Lina Yu, Hongxing Liu, Feng Xu, and Hongfei Wang
, 2005 ). In contrast, 10 °C does not cause chilling stress although it is still cold enough for peach storage. In a previous study, we compared soluble carbohydrates in peach fruits stored at 0 and 5 °C ( Wang et al., 2013 ). However, sugar metabolism in
An Qin, Xiaosan Huang, Huping Zhang, Juyou Wu, Jie Yang, and Shaoling Zhang
and chilling stresses via traditional cross-hybridization procedures. As a first step toward creation of pear transgenic plants with enhanced stress tolerance, efforts have been made to isolate and characterize PbDHAR2 gene in this study. Moreover
David A. French and Kirk L. Parkin
To examine the role of endogenous antioxidants in providing chilling stress protection, field-grown cucumber (Cucumis sativus L. cv. Eureka) fruit were stored in the dark and evaluated throughout storage. Storage treatments included continuous chilling (C) (5°C), continuous tempering (T) (12°C), intermittent warming (IW) (1 day at 12°C every 4 days) for 1, 2, 3, or 4 cycles, and preconditioning (PC) (12°C for 4 or 8 days) before chilling. Fruit exposed to in-field chilling (FC) were also stored under continuous chilling at 5°C. Samples were evaluated visually for tissue damage (lack of exudate, water-soaked appearance), and ascorbic acid (Asc) and reduced (GSH) and oxidized (GSSG) glutathione levels and glutathione reductase (GtR) and ascorbate free radical reductase (AFRR) activities were determined. Each 4 days of PC extended storage life by 7 days relative to C. FC or 1–2 IW cycles also extended storage life relative to C. With all treatments, Asc depletion preceded visual tissue damage, whereas GSH, GtR, and AFRR were not depleted before such damage. GSSG levels remained low throughout storage. GtR activity was elevated by FC and IW. AFRR activity was elevated by all treatments. Asc levels were elevated initially by all treatments, with this elevation lasting longer with PC and T. These results suggest that Asc levels decline during stress in the absence of an obvious lesion in the Asc regeneration scheme.
Ehiorobo Izekor, J.O. Garner, and F.B. Matta
A procedure to determined selection of sweetpotato (Ipomoea batatas L. Lam.) genotypes tolerant to chilling injury was initiated by crossing two resistance lines and two susceptible lines. Experimental design on the F1 progeny was a completely randomized design (CRD) with two groups, tolerant and sensitive genotypes, and 90 lines in each group. Four plants per lines were selected and each plant represented a replication. The rating of plants according to the degree of chilling injury was recorded at 36 h after chilling temperature of 5 °C with 85% relative humidity. Significance of the analysis was based on the number of plants tolerant to chilling injury from both the resistant and the sensitive groups. Results from the statistical analysis based on visual rating of the F1 progeny plants for 36 h, indicated that higher populations of resistant plants could be produced when two resistant lines were crossed in a control pollination process. Evaluations to be continued are chlorophyll fluorescence, leakage of cell content, structural changes of the cell, and peroxidase content, before and after chilling stress. These assays will be used to further determine the similarities among the chilling-tolerant genotypes. Findings will aid in elucidating mechanism of chilling injury in fruit and vegetables.
Milton E. Tignor Jr. and Russell L. Weiser
Alaska peas (Pisum sativum `Alaska') germinated in a dark growth chamber were treated ABA dissolved in a small amount of acetone before diluting in distilled water with 0.1% spreader. A blank solution was identically prepared without ABA. Both solutions were applied via paintbrush to the epicotyls of the peas every twelve hours for seven days following emergence. The blank solution was applied to two controls, chronological and physiological. A methanol bath was used to induce freezing and chilling stresses. ABA significantly improved cold tolerance (electrolyte leakage) in the pea seedlings for both freezing and chilling stress as compared to the physiological and chronological controls. Visual observation of the pea stems suggested a difference in stem flexibility among ABA treated peas and the controls. Pea stem elasticity and plasticity were measured along with plant dry weight, cell wall weight/gram fresh weight, and the quantity of cell wall sugars and amino acids.
Ann Fitzpatrick and Paul H. Jennings
Preliminary studies on the effects of chilling stress during the early stages of germination and radicle emergence in cucumber have suggested that damage may be due to the accumulation of active oxygen species. Several methods are available which are capable of assessing various types of oxidative damage and were selected for use in determining the involvement of active oxygen species in the chilling response of emerging cucumber roots. Oxygen radicals have been shown to interact with cellular proteins resulting in the formation of carbonyl derivatives. A procedure using 2,4-dinitrophenylhydrazine was tested to determine carbonyl protein content. Cellular lipids are also subject to peroxidation by active oxygen species resulting in the production of malondialdehyde and can be quantified by reaction with thiobarbituric acid. Sulfydryl groups may also be attacked by oxygen free radicals and changes monitored by a procedure using 5,5'-dithio-(2-nitrobenzoic acid). A comparison of these three methods for detecting oxidative damage associated with chilling stress in radicles of germinating cucumber seed will be discussed.
R. Savé, J. Peñuelas, I. Filella, and C. Olivella
One-year-old gerbera plants subjected to 1 night at 5C had reduced leaf water losses and chlorophyll content and increased root hydraulic resistance, but stomatal conductance and leaf water potential did not change. After 3 nights, leaf water potential had decreased and leaf reflectance in the visible and the near-infrared had increased. Similarly, abscisic acid (ABA) in leaves had increased and cytokinins (CK) in leaves and roots had decreased, but ABA levels in roots did not change. After 4 days at 20C, root hydraulic resistance, reflectance and leaf water loss returned to their initial values, but leaf water potential and chlorophyll content remained lower. Leaf ABA levels reached values lower than the initial, while root ABA and leaf CK levels retained the initial values. These data suggest that in the gerbera plants studied, 3 nights at 5C produced a reversible strain but otherwise plants remained uninjured, so this gerbera variety could be cultured with low energetic inputs under Mediterranean conditions. The results may indicate that ABA and CK were acting as synergistic signals of the chilling stress. Spectral reflectance signals seemed to be useful as plant chilling injury indicators at ground level.
Eleazar Reyes and Paul H. Jennings
Roots of `Golden Girl' squash (Cucurbita pepo var. melopepo) and `Encore' cucumber (Cucumis sativus L.), 4- and 3-days-old, respectively, were exposed to 2, 6, 10, and 15C for 24, 48, 96, 144, and 192 hours to compare the sensitivity to chilling temperatures and the subsequent recovery at more favorable temperatures. Seedlings were more sensitive to chilling at 2 and 6C when measured by their ability to resume growth when returned to 26C. Root growth decreased after 48 hours of chilling. Seedlings stressed at 10 and 15C were able to continue root growth at these temperatures and when returned to 26C. However, seedlings at 10C exhibited root-tip browning in both crop species, suggesting disfunction in metabolic pathways that were repressed in seedlings growing at 2C where those symptoms were not present. Effects on root dry weight occurred in the first 24 hours at all temperatures studied. After 96 hours of treatment, seedlings grown at 2 and 6C were irreversibly damaged, as evidenced by their inability to resume growth when returned to 26C. Leakage of electrolytes from squash and cucumber roots increased after 48 hours at 2C. Potassium, Na+, and PO4 -2 were lost in greater amounts than Mg+2, Cl-, and SO4 -2. No difference in ionic leakage occurred at 10 and 15C, and Ca+2 leakage was not detected at any chilling stress temperature.