Induction of Changes in Internal Gas Pressure of Bulky Plant Organs by Temperature Gradients

Abstract

<jats:p>Water manometers were connected to fruits of tomato <jats:italic>(Lycopersicon esculentum</jats:italic> Mill.) and pepper (Cap<jats:italic>sicum annuum</jats:italic> L.), and then fruits were submerged in water baths providing initial temperature gradients between fruit and water of 0 to 19C. Apple <jats:italic>(Malus domestics</jats:italic> Borkh.) fruits, carrot <jats:italic>(Daucus carota</jats:italic> L.) roots, witloof chicory <jats:italic>(Cichorium intybus</jats:italic> L.) roots, rhubarb <jats:italic>Rheum rhabarbarum</jats:italic> L.) petioles, and pokeweed <jats:italic>(Phytolacca americana</jats:italic> L.) stems were subjected to water bath temperature gradients of 5C. Internal partial vacuums developed in all organs within minutes of imposing the gradients. The maximum partial vacuums in tomato and pepper fruits increased with increasing temperature gradients. Uptake of water accompanied changes in internal pressure reaching maxima of 17% (w/w) and 2% (w/w) of pepper and tomato fruits, respectively, after 22 hours. Maximum pressure changes achieved in bulky organs deviated from those predicted by the ideal gas law, possibly due to concomitant changes in gas pressure upon replacement of intercellular spaces with water and dissolution of CO<jats:sub>2</jats:sub>. Partial vacuums also developed in pepper fruits, rhubarb petioles, and pokeweed stems following exposure to air 15C cooler than initial organ temperatures. Results point to the role of temperature gradients in the transport of liquids and gases in plant organs.</jats:p>

Physiological and genetic factors influencing fruit cracking

“…Fruit cooling, which occurs at night, would be expected to contract bulky fruits such as tomatoes (Corey and Tan 1990). This negative pressure could suck in moisture that is condensed or otherwise present on the fruit surface, and also could draw in moisture from the plant itself.…”

“…This negative pressure could suck in moisture that is condensed or otherwise present on the fruit surface, and also could draw in moisture from the plant itself. As temperatures rise during the day and the fruit heats up in the sun, positive pressures build inside the fruit, stretching the gasimpermeable tomato skin outward as the fruit expands in volume (Corey and Tan 1990). Presumably, the greater the day/night differential, the greater the stress on the skin.…”

“…The effects of humidity on tomato fruit cracking may be related to water and gas pressure increases. The tomato skin is 97 % gas-impermeable (Corey and Tan 1990). As gas and water pressures increase in the fruit because of a temperature increase or an increase in water supply, the only way this outward pressure can be relieved is if the skin expands or if water is drawn out of the fruit and back into the plant (Peet 1992).…”

Internalization of Salmonella enterica by tomato fruit

“…If a fruit with water pooled over the stem scar cools, then a reduction of internal gas pressure can produce vacuums sufficient to draw the water into fruit. Dwell time and temperature differential both directly affect the amount of water absorbed in this manner (Bartz, 1982;Corey & Tan, 1990;Vigneault, Bartz, & Sargent, 2000). Theoretically, as the temperature differential increases, the volume of water entering a fruit increases (Bartz, 1999) although just as there is a finite amount of internal free space, there is a finite limit to the volume of water that can enter that space.…”

“…External water can flood into these apertures due to hydrostatic pressure, a physical force directed on fruit surfaces during contact with water including fruit dumped into water, fruit struck by rainfall, overhead irrigation or wash-water or fruit submerged under water. External water can also be drawn into surface apertures due to internal vacuums that develop when gasses within a fruit's apoplastic free space cool leading to pressure gradients between the cuticle surface and internal storage tissues (Corey & Tan, 1990). Infiltration is likely when aqueous films cover a cooling fruit's surfaces such as those surrounding a submerged tomato fruit.…”