Search Results

You are looking at 1 - 10 of 11 items for

  • Author or Editor: L. V. Gusta x
Clear All Modify Search
Author:

Plants acclimate to abiotic stresses, e.g. heat, freezing drought and salinity, in response to environmental cues such as temperature, daylength and water. Plants can respond within minutes to the cue e.g. heat tolerance or within hours or days, e.g. drought and freezing tolerance. Heat shock proteins are measurable within 20 to 30 minutes of a heat stress and the plants aclimate almost immediately. In contrast, proteins related to freezing tolerance are measurable within hours but days are required before a measurable increase in freezing tolerance can be detected. In almost all stresses it appears that the environmental cue effects the water status of the plant which in turn affects the level of endogenous abscisic acid (ABA). ABA has been implicated to ameliorate the stress by inducing genes to produce stress proteins. There is a certain degree of commodity between stresses in ragards to stress proteins, however each stress has their own unique set of stress proteins. For example heat shock proteins did not confer stress tolerance. Proteins involved in water and osmotic stress tolerance share a high degree of commonality. I” all stresses a unique class of proteins are synthesized which are classified as heat or boiling stable (do not coagulate at 100°). These proteins are suggested to be involved in the stress response. Many of these heat stable proteins are induced by ABA alone or in combination with jasmonic acid (JA). Analogs of ABA which are either slowly converted to ABA or are degraded slowly or taken up at a faster rate than ABA have been tested for the efficacy in inducing the stress responses. Analogs have also been identified which inhibit the ABA induced response. How these analogs may have practical significance will be discussed.

Free access
Authors: and

Abstract

The supercooling of flower primordia within dormant peach buds [Prunus persica (L.) Batsch.] is dependent on water migration from the base of the flower primordium to preferential sites of freezing in the flower bud scales and pith during the initial stages of freezing. The preferential freezing that occurs in the flower bud scales and pith does not appear to be caused by a difference in distribution of ice nucleators. The mean nucleation temperature of the flower bud increased with the amount of attached shoot, an indication that ice nucleation began in the shoot and spread into the flower bud. The flower primordium, however, appeared to have an intrinsic resistance to ice nucleation in comparison to other parts of the flower bud, which may be related to its lower water and osmotic potentials. The reduced osmotic potential of the flower primordium could be a consequence of significantly higher sucrose levels on a dry weight basis compared to that of the vascular tissue below the flower buds or that of the flower bud scales. A gradient in water potential between the xylem of the shoot and the flower bud also existed and may account for the recovery of water that is lost from the flower bud during freezing.

Open Access

Abstract

Low temperatures (LT) exotherms were found by differential thermal analysis (DTA) at −30°C in ‘Siberian C’ peach (Prunus persica [L.] Batsch) and −39° in ‘Starkrimson Delicious’ apple (Malus domestica Borkh. Nuclear magnetic resonance (NMR) spectrometry of intact stems and isolated bark and wood revealed that the LT exotherm was produced by freezing of deep supercooled water which was detected in the wood but not the bark. Freezing processes of the wood and bark appeared to be independent. In both species, xylem injury occurred at the same temperature as the LT exotherm and was closely, if not causally related to freezing of the supercooled water. Bark injury also occurred at the same temperature as the LT exotherm and may have been caused by dehydration stress or freezing of a small amount of supercooled water which remained undetected by NMR spectrometry. The dehydration resistance of apple wood on desiccation at 70 to 90% relative humidity was greater than that of the peach wood which in turn was greater than that of the bark of both species. The dehydration resistance of apple and peach wood may involve both nonliving and living elements of the wood because pulverizing the tissue destroyed the effect, whereas heat killing only lowered it. Both supercooling and dehydration resistance may be related to microcapillary pore structure which restricts heterogeneous nucleation and sublimation of supercooled water from the ray parenchyma cells.

Open Access

Abstract

A freezer system is described for subjecting biological materials to temperatures between +50° and -85°C. The system provides for removal of latent heat of fusion, adjustment of tissue water content, uniformity of temperature, control of supercooling and a wide range of cooling rates.

Open Access

Abstract

Either imbibition at low temperatures or fast water uptake reduced germination of chickpea (Cicer arietinum L.) by 15%. The combination of imbibition at low temperatures and fast water uptake reduced germination by 65%. The most chilling-sensitive period for chickpea germination is the first 30 minutes of imbibition. Slow imbibition at 20°C for 24 hours prior to seeding of mechanically damaged chickpea seeds significantly improved percentage of germination, and uniform, vigorous seedlings resulted. Such prehydrated seeds also showed better emergence under field conditions, especially in early spring when the soil was still cold. The results suggest that mechanically damaged seeds sown in cold, wet soil undergo imbibitional chilling injury and fast water uptake, leading to poor field emergence. Prehydration of seeds by slow imbibition at warm temperature and/or fungicide application increased the germination and emergence of chickpeas sown into cold, wet soils.

Open Access

Abstract

Leaves of cold-acclimated lemon [Citrus limon (L.) Burm. f.], grapefruit (C. paradisi Macf.), orange [C. sinensis (L.) Osbeck], and mandarin (C. unshiu Marc.) trees ranged in cold hardiness from −4 to −11°C. No significant differences in water content (g H2O/g dry weight) or melting point depression were observed. Plots of liquid water content during freezing (g H2O/g dry weight) vs. temperature were similar for the 4 citrus species. The tissues apparently deviated from ideal freezing behavior because less ice was formed. The reduced ice formation could not be accounted for by osmotic effects. Negative pressure potential developed during freezing is hypothesized to play a role in tissue water potential in frozen systems. It was concluded that hardier Citrus leaves survive freezing of a larger fraction of their tissue water.

Open Access

Abstract

In the paper “Imbibitional Chilling Injury during Chickpea Germination” by Tony H.H. Chen, S.D.K. Yamamoto, L.V. Gusta, and A.E. Slinkard [J. Amer. Soc. Hort. Sci. 108(6):944–948, 1983], on page 946, Fig. 2 was omitted inadvertently during printing. The missing photograph and its caption appear below:

Open Access

Abstract

The cold hardiness of 6 cool season grass genera was compared in mid-winter under controlled freezing conditions. Creeping bentgrasses (Agrostis palustris Huds.) tolerated the lowest temperatures whereas perennial ryegrasses (Lolium perenne L.) was the least hardy. Kentucky bluegrass (Poa pratensis L.) readily loses cold hardiness when exposed to warm conditions and did not reharden when exposed to cool temperatures. Appreciable hardiness in Kentucky bluegrass was induced by simulating drought conditions.

Open Access

Seeds of celery, spinach, onion, cress, water cress, iceberg lettuce, Great Lakes lettuce, cabbage, tomato, sweet corn and celery were pre-treated with 0.1 μM/g seed of both ABA and analogs of ABA. The chemicals were dissolved in a mixture of methanol:hexane (9:1/v:v) and applied to the seeds for approximately 3 minutes. The solvent was removed from the seeds within 5 minutes by rotary evaporation under reduced pressure. Effects on petri plate germination and soil emergence were monitored daily at 5, 10 and 15°C. The methanol/hexane solvent alone improved spinach seed emergence at 10°C from 10% to 100% and from 50% to 90% at 15°C in celery. Certain ABA analogs reduced time to 50% emergence in celery by at least 7 days at 15°C. Two ABA analogs synchronized emergence in celery and effect was temperature-dependent. One analog improved seed germination in tomato from 15% to 90% at 10°C. In most cases treatment effects on radicle germination on petri plates was not a good indicator of treatment effects on emergence from a soil based system.

Free access