Temperature Effects on Oxidative Metabolism of Dormant Sugar Pine Seeds

Abstract

When dormant sugar pine (Pinw lamberdaea L.) seeds were imbibed at 5°C, they showed a rapid increase in 02 uptake, ATP level, and moisture content during the first 4 days. This was followed by a plateau phase until 60 days, after which a second significant increase in all three features occurred as dormancy was broken. During the plateau phase, conventional CN-sensitive respiration accounted for 74 to 79% of the total 02 uptake.When dormant sugar pine seeds were imbibed at and maintained at 25°C, a different pattern occurred. Water uptake was much more rapid during the first 4 days and no second increase occurred after 60 days because the seeds did not break dormancy. There was an initial burst of 02 uptake and ATP formation, but these both declined abruptly after 24 to 48 hours. Levels about half those of seeds at 5°C were maintained through the rest of a 90-day period. CN-sensitive respiration declined during imbibition at 25°C, and accounted for only 55 to 61% of the total 02 uptake. The inability of dormant sugar pine seeds to germinate at temperatures above about 170C may therefore result from initial temperature effects on membrane prpties, leading to reduced 02 uptake, reduced cytochrome oxidase electron transport activity, and lowered ATP levels.There is an extreme paucity of information about basic metabolic changes occurring during stratification of dormant pine seeds. We have determined previously that changes in inhibitor content during stratification of sugar pine seeds could not be causally related to loss of dormancy (12,13), which supports current concepts that membrane properties or regulatory metabolism may also be involved in the control of seed dormancy and germination (7, 1 1).We recently observed that the temperature during imbibition of sugar pine embryos had a significant effect on rates of water influx and solute efflux. Temperatures above 17°C, at which sugar pine seeds do not normally germinate, caused abnormally high rates of water uptake and solute leakage to occur, possibly due to temperature effects on membrane properties (14). This appears similar in nature to the injurious effect of elevated temperatures and humidity in accelerated aging treatments (1, 15) and the deleterious effect of cold temperatures on chilling-sensitive species (8,10,17 investigation was to determine whether a similar series of metabolic dysfunctions occurs at the moderate temperatures at which the apparent effect on membrane properties was observed in sugar pine embryos. MATERIALS AND METHODSSeeds of sugar pine (Pinus lambertiana L. ) were obtained from Schumacher (Sandwich, MA). Intact seeds were imbibed in 5 mm phosphate buffer (pH 7.2) for 24 h at either 5 or 25°C, blotted dry, and then treated with 0.1% (w/w) Arasan 50-Red (DuPont).Seeds were then placed in plastic bags with moist paper towels and maintained at either 5 or 25°C. At 1, 2, 4, 7, 14, 30, 60, and 90 d, embryos were excised from the seeds for determination of moisture content, respiration rates and pathways, and ATP levels. The possi...

Genes associated with the release of dormant buds in tree peonies (Paeonia suffruticosa)

“…Our results also imply that the up regulated transcription level of PsPII may promote dormancy release by increasing the content of carbohydrate and make the dividing cells pass G1 stage to S stage. It has been proved that the level of ATP changed obviously during the chilling treatment to break buds/seeds dormancy (Krawiarz and Szczotka 2005;Murphy and Noland 1982). The buds/seeds entered into dormancy contained very low level of ATP.…”

The involvement of mitochondrial phosphate transporter in accelerating bud dormancy release during chilling treatment of tree peony (Paeonia suffruticosa)

“…SuYcient chilling treatment is often required to break the bud dormancy for numerous horticultural plants (Henzell et al 1991;Anderson et al 2005;Chao et al 2006). The level of ATP was aVected obviously during the chilling treatment to break bud/seed dormancy (Murphy and Noland 1982;Krawiarz and Szczotka 2005). The buds/seeds that entered dormancy contained very low level of ATP.…”

Priming and temperature limits for germination of dispersal units of Urochloa brizantha (Stapf) Webster cv. basilisk

“…Relatively low priming temperatures caused lower water content (WC), whereas imbibition in PEG (-0.5 MPa) tended to reduces WC as compared to distilled water, although no effect of the osmotic medium was observed at relatively low (8 °C and 20 °C) priming temperatures. That response was expected since earlier reports show that temperature affect the rates of water uptake primarily by changing the water viscosity, although the increase in water uptake with temperature can be discontinuous from 5 °C to 35 °C as reported for pine embryos in which the slope of the regression line of the water uptake on temperature was significantly steeper above 20 °C (Murphy and Noland, 1982). Once the previously imbibed U. brizantha seeds were dried for 72h at 25 °C the seed water content was found to be similar among priming treatments within each assay, ensuring that WC was similar among the seeds before use in the germination tests.…”