scholarly journals 717 PB 423 ETHYLENE DEGASSING OF GRAPEFRUIT

HortScience ◽  
1994 ◽  
Vol 29 (5) ◽  
pp. 535g-536
Author(s):  
Peter D. Petracek
Keyword(s):  
Gas Exchange ◽  
Silicone Rubber ◽  
Water Loss ◽  
Fruit Color ◽  
Water Soluble ◽  
Chlorophyll Degradation ◽  
Initial Exposure ◽  
Early Season ◽  
Flow Through

Early-season fresh citrus are routinely exposed to ethylene to trigger chlorophyll degradation (degreening) in the peel and thus improve fruit color. Recent questions about whether ethylene is trapped in the fruit by subsequent waxing have sparked interest in characterizing ethylene exchange. Internal gas samples of mature, pesticide-free `White Marsh' grapefruit were taken through septa of silicone rubber on electrical tape affixed 10 the blossom end. Gassing of the fruit in a degreening room (10 ppm ethylene) required about four hours lo reach equilibrium while degassing was completed in less than two hours and was not affected by location of the fruit in a 0.680 m3 pallet bin. Waxing with a water-soluble wax immediately following ethylene exposure increased the time for complete degassing to over 48 h. Surface gas exchange protiles were prepared by sequentially analyzing the same fruit after: (1) harvest, (2) 22 h exposure to 10 ppm ethylene, (3) exposure to ethylene and washing with an ionic cleaning surfactant, and (4) exposure to ethylene and waxing. Glass cells with interfacing silicone rubber o-rings (23 mm diam.) were strapped to the fruit following each treatment. Ethylene emanation was measured by sampling the cells which were capped 15 m after removal from ethylene. Water and CO2 were measured by flow-through cells following ethylene analysis. Ethylene emanation following the initial exposure was the same for the stem end and midsection and two fold greater than the blossom end. Washing increased the rate of emanation five fold for the stem end and about 2.5 fold for the midsection and blossom end. Waxing reduced emanation by nearly four fold for the midsection and blossom end, but only 30% for the stem end. Water loss was increased about 40% by washing, reduced about 30% by waxing, and was primarily through the stem end. Stem-end CO2 exchange doubled upon waxing.

Ant breathing: testing regulation and mechanism hypotheses with hypoxia

1995 ◽  
Vol 198 (7) ◽  
pp. 1613-1620 ◽  
Author(s):  
J Lighton ◽  
D Garrigan
Keyword(s):  
Gas Exchange ◽  
Water Loss ◽  
Negative Pressure ◽  
Co2 Emission ◽  
Nitrogen Accumulation ◽  
Phase Duration ◽  
O2 Concentration ◽  
Flow Through ◽  
Discontinuous Gas Exchange Cycle ◽  
And Function

Using normoxic and hypoxic flow-through respirometry, we investigated the regulation of the closed-spiracle (C) and the nature of the fluttering-spiracle (F) phases of the discontinuous gas-exchange cycle (DGC) of the ant Camponotus vicinus. We predicted that as ambient O2 concentrations declined, DGC frequency would increase, because C phase duration would decrease (reflecting earlier hypoxic initiation of the F phase) and F phase duration would shorten (reflecting nitrogen accumulation), if convective mass inflow caused by a negative pressure gradient across the spiracles, rather than by diffusion, is the dominant F phase gas-exchange mechanism. C phase duration decreased with declining ambient O2 concentrations, as predicted. In contrast, DGC frequency decreased and F phase duration increased with decreasing ambient O2 concentrations. This was opposite to the expected trend if gas exchange in the F phase was mediated by convection, as is generally hypothesized. We therefore cannot disprove that F phase gas exchange was largely or purely diffusion-based. In addition, our data show equivalent molar rates of H2O and CO2 emission during the F phase. In contrast, during the open-spiracle phase, the duration of which was not affected by ambient O2 concentration, far more H2O than CO2 was lost. We discuss these findings and suggest that current hypotheses of F phase gas-exchange mechanisms and function in reducing respiratory water loss in adult insects may require revision.

scholarly journals Intra-individual variation allows an explicit test of the hygric hypothesis for discontinuous gas exchange in insects

2009 ◽  
Vol 6 (2) ◽  
pp. 274-277 ◽  
Author(s):  
Caroline M. Williams ◽  
Shannon L. Pelini ◽  
Jessica J. Hellmann ◽  
Brent J. Sinclair
Keyword(s):  
Carbon Dioxide ◽  
Gas Exchange ◽  
Metabolic Rate ◽  
Water Loss ◽  
Individual Variation ◽  
Loss Reduction ◽  
Total Water ◽  
Explicit Test ◽  
Carbon Dioxide Release ◽  
Flow Through

The hygric hypothesis postulates that insect discontinuous gas exchange cycles (DGCs) are an adaptation that reduces respiratory water loss (RWL), but evidence is lacking for reduction of water loss by insects expressing DGCs under normal ecological conditions. Larvae of Erynnis propertius (Lepidoptera: Hesperiidae) naturally switch between DGCs and continuous gas exchange (CGE), allowing flow-through respirometry comparisons of water loss between the two modes. Water loss was lower during DGCs than CGE, both between individuals using different patterns and within individuals using both patterns. The hygric cost of gas exchange (water loss associated with carbon dioxide release) and the contribution of respiratory to total water loss were lower during DGCs. Metabolic rate did not differ between DGCs and CGE. Thus, DGCs reduce RWL in E. propertius , which is consistent with the suggestion that water loss reduction could account for the evolutionary origin and/or maintenance of DGCs in insects.

scholarly journals Respiratory Strategies in Relation to Ecology and Behaviour in Three Diurnal Namib Desert Tenebrionid Beetles

Insects ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1036
Author(s):  
Frances D. Duncan
Keyword(s):  
Gas Exchange ◽  
Water Loss ◽  
Evaporative Cooling ◽  
Respiratory Physiology ◽  
Metabolic Rates ◽  
Beetle Species ◽  
Water Droplets ◽  
Namib Desert ◽  
Flow Through

The respiratory physiology of three diurnal ultraxerophilous tenebrionid beetles inhabiting either the dune slipface or gravel plain in the Namib Desert was investigated. The role of the mesothoracic spiracles and subelytral cavity in gas exchange was determined by flow-through respirometry. All three species exhibited the discontinuous gas exchange cycles with a distinct convection based flutter period and similar mass specific metabolic rates. There was variation in their respiration mechanics that related to the ecology of the species. The largest beetle species, Onymacris plana, living on the dune slipface, has a leaky subelytral cavity and used all its spiracles for gas exchange. Thus, it could use evaporative cooling from its respiratory surface. This species is a fog harvester as well as able to replenish water through metabolising fats while running rapidly. The two smaller species inhabiting the gravel plains, Metriopus depressus and Zophosis amabilis, used the mesothoracic spiracles almost exclusively for gas exchange as well as increasing the proportional length of the flutter period to reduce respiratory water loss. Neither species have been reported to drink water droplets, and thus conserving respiratory water would allow them to be active longer.

scholarly journals Chronicvs.Short-Term Acute O3Exposure Effects on Nocturnal Transpiration in Two Californian Oaks

2007 ◽  
Vol 7 ◽  
pp. 134-140 ◽  
Author(s):  
N. E. Grulke ◽  
E. Paoletti ◽  
R. L. Heath
Keyword(s):  
Gas Exchange ◽  
Water Loss ◽  
Exchange System ◽  
Short Term ◽  
Blue Oak ◽  
Unexposed Control ◽  
Nocturnal Transpiration ◽  
Gas Exchange System ◽  
Black Oak ◽  
Oak Seedlings

We tested the effect of daytime chronic moderate ozone (O3) exposure, short-term acute exposure, and both chronic and acute O3exposure combined on nocturnal transpiration in California black oak and blue oak seedlings. Chronic O3exposure (70 ppb for 8 h/day) was implemented in open-top chambers for either 1 month (California black oak) or 2 months (blue oak). Acute O3exposure (~1 h in duration during the day, 120–220 ppb) was implemented in a novel gas exchange system that supplied and maintained known O3concentrations to a leaf cuvette. When exposed to chronic daytime O3exposure, both oaks exhibited increased nocturnal transpiration (without concurrent O3exposure) relative to unexposed control leaves (1.8× and 1.6×, black and blue oak, respectively). Short-term acute and chronic O3exposure did not further increase nocturnal transpiration in either species. In blue oak previously unexposed to O3, short-term acute O3exposure significantly enhanced nocturnal transpiration (2.0×) relative to leaves unexposed to O3. California black oak was unresponsive to (only) short-term acute O3exposure. Daytime chronic and/or acute O3exposures can increase foliar water loss at night in deciduous oak seedlings.

Effects of Neem EC on gas exchange, tracheal ventilation, and water loss in diapausing pupae ofPieris brassicae

2008 ◽  
Vol 126 (2) ◽  
pp. 165-173 ◽  
Author(s):  
Katrin Jõgar ◽  
Aare Kuusik ◽  
Luule Metspalu ◽  
Külli Hiiesaar ◽  
Maria Grishakova ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Water Loss
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