Influence of Ice Encasement and Ethylene Regulation on Cellular-protection Responses in Annual Bluegrass

Abstract

Annual bluegrass (Poa annua var. reptans), when grown as a putting green species, is sensitive to winter injury such as ice cover. Inhibiting plant ethylene production could be a way to improve annual bluegrass tolerance of ice encasement. The goals of this study were to determine how winter conditions and ethylene regulatory treatments affect the antioxidant system, fatty acid composition, and apoplastic proteins of annual bluegrass plant tissues. Ethylene-promotive (1-aminocyclopropane-1-carboxylic acid or ethephon) and ethylene inhibition treatments [aminoethoxyvinylglycine (AVG)] were applied to plants in the field during acclimation. Plant plugs were taken and subjected to low temperature (−4 °C) and ice-encasement treatments in growth chamber conditions. Antioxidant activities of ascorbate peroxidase (APX), peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) were measured along with malondialdehyde content (MDA) and apoplastic protein content in leaf and crown tissue. Saturated and unsaturated fatty acid contents were measured in leaf, crown, and root tissue. Higher unsaturated fatty acids are often associated with greater low-temperature tolerance. Compared with the untreated controls, ethephon-treated annual bluegrass had greater MDA contents, lower POD and SOD activity, and greater saturated and decreased unsaturated fatty acids. Ethylene inhibition treatments caused annual bluegrass to have less saturated fatty acid content and greater unsaturated fatty acid content, a greater content of apoplast proteins, and higher CAT activity when compared with the untreated controls. The activity of APX was greater in AVG-treated annual bluegrass than in controls. Ethylene may reduce physiological health overwinter, and inhibitory treatments may promote winter tolerance by promoting antioxidant activity, apoplast proteins, and the content of unsaturated fatty acids in plant tissues.

Leaf, Root, and Crown Tissue Physiology of Annual Bluegrass after Cold Acclimation at Varying Soil Moisture Levels and Ice Encasement

“…The lack of damage to root tissue membranes observed here and the enhanced levels of carbohydrates observed during dry soil conditions compared with greater levels of soil moisture may warrant a need for more investigations of root acclimation, survival, and overwintering in annual bluegrass, particularly in field conditions. In leaf tissue of plants exposed to 40 and 80 d of ice encasement at -3 C, MDA content was higher compared with in 0-d plants not exposed to ice encasement and prolonged time at -3 C. Our results are consistent with the increase in MDA content found in crown and leaf tissues of annual bluegrass in response to low-temperature duration with no ice encasement and in ice-encased plants (Laskowski and Merewitz 2021). Cold acclimation and extended durations of plant tissues in cold temperatures can cause reactive oxygen species generation and lipid peroxidation, particularly given that cold temperatures influence membrane fluidity, stability, and dynamic regulation of fatty acid metabolism (Gill and Tuteja 2010).…”

“…Anoxic conditions, often found during prolonged ice encasement, can cause lipid peroxidation, particularly after plant reaeration, and less lipid peroxidation is associated with greater tolerance of anoxic conditions (Blokhina et al 1999(Blokhina et al , 2001. In annual bluegrass, Laskowski and Merewitz (2021) found that leaf and crown tissues had similar levels of lipid peroxidation after cold acclimation and overwintering stresses. Lipid peroxidation levels increased in both tissues following 80 d of cold temperatures or ice encasement treatment.…”

Impact of Preharvest Ethephon Foliar Spray on the Postharvest Fatty Acid Profile and Dietary Indicators of Macadamia Nuts

“…These findings are consistent with previous studies by [22], which also reported an increase in saturated fatty acids and a decrease in unsaturated fatty acids in response to ethylene treatment [22]. Another study by [23] also reported that the use of ethylene may reduce unsaturated fatty acids. In this study, we observed a significant decrease in unsaturated fatty acids in ED, particularly Eicosatrienoic acid + Erucic acid (C20:3n 3 + C22:1) and Eicosatrienoic acid + Alpha-linolenic acid (C20:1 + C18:3n 3 ).…”

Current Outlook on Ice Encasement Stress and Management Strategies in Turfgrasses

“…Additional investigation into turfgrass responses to reaeration following ice encasement (i.e., at lower and increasing temperatures) is needed. Laskowski and Merewitz (2021) found that low temperature alone [À4 C (24.8 F)] and ice encasement at À4 C caused an increase in lipid peroxidation to similar levels in both leaves and crown tissue. Unexpectedly, crowns were not more resilient to the development of lipid peroxidation than leaves in that study.…”

“…It is not yet clear whether these treatments are directly influencing ice encasement-related stresses, such as toxic gas tolerance or anoxia tolerance, or are indirectly promoting ice encasement survival via altered acclimation traits. Laskowski and Merewitz (2021) found that some chemical treatments, such as a mineral oil product (Civitas), did influence the response of the antioxidant system and had greater membrane health following ice encasement, which could correlate to greater levels of regrowth during the post ice encasement reaeration.…”