scholarly journals The transpiration and respiration as mechanisms of water loss in cold storage of figs

Food Research ◽  
2021 ◽  
Vol 5 (6) ◽  
pp. 109-118
Author(s):  
D. Lentzou ◽  
G. Xanthopoulos ◽  
C. Templalexis ◽  
A. Kaltsa
Keyword(s):  
Relative Humidity ◽  
Water Vapour ◽  
Cold Storage ◽  
Water Loss ◽  
Vapour Pressure ◽  
Vapour Pressure Deficit ◽  
Agricultural Products ◽  
Water Vapour Pressure ◽  
The Difference ◽  
Water Vapour Pressure Deficit

Transpiration and respiration are two mechanisms of water loss in fresh agricultural products, resulting in visual and texture degradation. Neglecting respiration as a mechanism of water loss may lead to erroneous results at saturation where water vapour pressure deficit is zero and thus water loss is expected to be zero, however, the existence of a finite water loss is noted. In this context, an analysis of the associated with transpiration and respiration water loss in figs (Ficus carica L.) was carried out at 0oC, 10oC and 20oC and 45.64%, 80.22% and 98.65% relative humidity as well as the air conditions of walk-in cold storage rooms. The estimated transpiration rate ranged between 0.11-1.416 mg cm-2 h -1 for a water vapour pressure deficit of 0.0-0.98 kPa. The water vapour pressure deficit estimation was based on the difference between cold air temperature and figs’ surface temperature. The respiration rate was calculated at 0oC, 10oC and 20oC as 0.47±0.08, 0.94±0.11 and 2.69±0.17 mLCO2100g-1 h -1 . Quantification of the water loss showed that at 20oC and saturation, the water loss due to respiration accounts for 3.9% of the respective water loss due to water vapour pressure deficit while on average, the water loss due to respiration accounts for 1.5%, 2.1% and 2.6% of the water loss due to water vapour pressure deficit at 0oC, 10oC and 20oC.

scholarly journals Can birds do it too? Evidence for convergence in evaporative water loss regulation for birds and mammals

2017 ◽  
Vol 284 (1867) ◽  
pp. 20171478 ◽  
Author(s):  
E. C. Eto ◽  
P. C. Withers ◽  
C. E. Cooper
Keyword(s):  
Water Vapour ◽  
Water Loss ◽  
Vapour Pressure ◽  
Vapour Pressure Deficit ◽  
Ambient Air ◽  
Evaporative Water Loss ◽  
Water Vapour Pressure ◽  
Evaporative Heat Loss ◽  
Evaporative Water ◽  
Water Vapour Pressure Deficit

Birds have many physiological characteristics that are convergent with mammals. In the light of recent evidence that mammals can maintain a constant insensible evaporative water loss (EWL) over a range of perturbing environmental conditions, we hypothesized that birds might also regulate insensible EWL, reflecting this convergence. We found that budgerigars ( Melopsittacus undulatus ) maintain EWL constant over a range of relative humidities at three ambient temperatures. EWL, expressed as a function of water vapour pressure deficit, differed from a physical model where the water vapour pressure deficit between the animal and the ambient air is the driver of evaporation, indicating physiological control of EWL. Regulating EWL avoids thermoregulatory impacts of varied evaporative heat loss; changes in relative humidity had no effect on body temperature, metabolic rate or thermal conductance. Our findings that a small bird can regulate EWL are evidence that this is a common feature of convergently endothermic birds and mammals, and may therefore be a fundamental characteristic of endothermy.

scholarly journals Comparison of vapour pressure deficit patterns during cucumber cultivation in a traditional high PE tunnel greenhouse and a tunnel greenhouse equipped with a heat accumulator

2018 ◽  
Vol 16 (1) ◽  
pp. e0201 ◽  
Author(s):  
Paweł J. Konopacki ◽  
Waldemar Treder ◽  
Krzysztof Klamkowski
Keyword(s):  
Air Temperature ◽  
Vapour Pressure ◽  
Vapour Pressure Deficit ◽  
Optimal Level ◽  
Water Vapour Pressure ◽  
Heat Accumulator ◽  
Climate Conditions ◽  
Excessive Heat ◽  
Protected Cultivation ◽  
The Difference

Plant productivity in protected cultivation is highly influenced by air temperature and humidity. The conditions relating to the moisture content of the air in protected plant cultivation are preferably defined by vapour pressure deficit (VPD), which describes the difference between the maximal and actual water vapour pressure (kPa). VPD is widely used as the parameter describing the climate conditions favourable for the development of fungal diseases and for highlighting conditions unfavourable for plant development. In protected cultivation, both the air temperature and the humidity are influenced by heating systems, and one such system is a heat accumulator, which may store the excessive heat produced during the day by converting the solar energy inside the plastic tunnel, and using it when plant heating is required. The tunnel equipped with a heat accumulator maintained an optimal level of humidity for a longer period, and significantly reduced the time of excessive air humidity. The longest time with an optimal VPD was recorded in August in a tunnel with an accumulator – 30.5% of total time vs. 22.3% of time for control tunnel. The highest difference of total time where the VPD was too low (below 0.2 kPa) was recorded in July – 12.4% of time in a tunnel with an accumulator vs. 39.1% of time for control tunnel. The highest difference of total time with an excessive VPD (over 1.4 kPa) was recorded in May – 12.1% of time in a tunnel with an accumulator vs. 17.9% of time for control tunnel. However, a situation beneficial for plant growth occurred every month during the investigated season.

Sweating in sheep

1960 ◽  
Vol 11 (4) ◽  
pp. 557 ◽  
Author(s):  
AH Brook ◽  
BF Short
Keyword(s):  
Weight Gain ◽  
Water Vapour ◽  
Vapour Pressure ◽  
Water Movement ◽  
Maximum Amount ◽  
Sweat Glands ◽  
Water Vapour Pressure ◽  
Average Weight ◽  
The Difference ◽  
Average Weight Gain

Water loss from the sweat glands of shorn sheep was estimated as the difference between the average weight gain of desiccating capsules placed on 10 normal sheep and on 4 control sheep congenitally lacking sweat glands. At an air tempera ture of 20°C (68°F) and a water vapour pressure of 12.5 mm Hg the rate of svveating was 10.2 g/m2/hr, and at 40°C (104°F) and a water vapour pressure of 28.1 mm Hg the rate of sweating was 32.1 g/m2/hr. The maximum amount of heat a sheep could lose by sweating at the rate of 32 g/m2/hr under these conditions is c. 20 kcal/hr. It is emphasized that the rate of sweating observed in shorn sheep must not be applied unreservedly to sheep with a fleece, because the dynamics of water movement in the fleece are unknown.

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