Daily and seasonal variation in hydric conditions and temperature inside nests of common snapping turtles (Chelydra serpentina)

1985 ◽  
Vol 63 (10) ◽  
pp. 2422-2429 ◽  
Author(s):  
Gary C. Packard ◽  
Gary L. Paukstis ◽  
Thomas J. Boardman ◽  
William H. N. Gutzke
Keyword(s):  
Seasonal Variation ◽  
Water Potential ◽  
Water Relations ◽  
Chelydra Serpentina ◽  
Fair Weather ◽  
Diel Cycles ◽  
Water Potentials ◽  
Snapping Turtles ◽  
Warm Weather ◽  
Heavy Rainfalls

Water potential and temperature are interrelated variables that must be studied simultaneously to gain insight concerning the water relations of reptilian eggs incubating in subterranean nests. We measured these variables inside nests of common snapping turtles (Chelydra serpentina) using thermocouple psychrometry. Water potentials in nests were high after heavy rainfalls, but declined during periods of fair weather. Likewise, temperatures in nests increased progressively during intervals of warm weather, but declined abruptly during cool periods accompanied by overcast and precipitation. On clear days, diel cycles in temperature occurred at the top, in the middle, and at the bottom of nests, but the cycles were slightly out of phase and their amplitudes decreased with increasing depth. These cycles in temperature drove cycles in evaporation–condensation of water that led in turn to complex cycles in diffusion of vapour. Net movement of vapour was into nests on some occasions, but out of them on others. Transport of liquid occurred also in the vicinity of nests, but probably was less important than transport of vapour as a means for translocating water. The eggs themselves influenced water potentials and vapour pressures in the vicinity of their nests and thereby elicited different movements of water in their immediate surroundings than occurred in the soil at large.

Water relations of pliable-shelled eggs of common snapping turtles (Chelydra serpentina)

1980 ◽  
Vol 58 (8) ◽  
pp. 1404-1411 ◽  
Author(s):  
Gary C. Packard ◽  
Theodore L. Taigen ◽  
Mary J. Packard ◽  
Thomas J. Boardman
Keyword(s):  
Water Vapour ◽  
Water Relations ◽  
Liquid Water ◽  
Water Loss ◽  
Considerable Importance ◽  
Chelydra Serpentina ◽  
Snapping Turtles ◽  
Transpirational Water Loss

Pliable-shelled eggs of common snapping turtles were incubated at 29 °C under hydric conditions simulating those to which eggs are exposed in natural nests. Eggs exposed to conditions similar to those encountered at the centre of nests experienced net declines in mass during incubation, presumably owing to the loss of water vapour to air trapped inside the chamber. Eggs exposed to conditions similar to those encountered at the periphery of nests absorbed liquid water across that part of their shell contacting the substrate and increased in mass during the early weeks of incubation. However, transpirational water loss from exposed surfaces of these eggs seemed to increase coincident with metabolism of developing embryos, and became high enough by the midpoint of incubation that absorption of liquid water could not compensate for the loss of water vapour, thereby causing eggs to decline in mass for the remainder of incubation. The size of hatchlings was related both to the position of eggs inside the chamber and to wetness of the substrate, indicating that the water exchanges of pliable-shelled eggs of snapping turtles may be of considerable importance to developing embryos.

The Water Relations of Allosyncarpia ternata (Myrtaceae) at Contrasting Sites in the Monsoonal Tropics of Northern Australia

1997 ◽  
Vol 45 (2) ◽  
pp. 259 ◽  
Author(s):  
I. R. Fordyce ◽  
G. A. Duff ◽  
D. Eamus
Keyword(s):  
Seasonal Variation ◽  
Stomatal Conductance ◽  
Water Potential ◽  
Water Relations ◽  
Leaf Water Potential ◽  
Dry Season ◽  
Leaf Water ◽  
Northern Australia ◽  
Leaf Water Relations ◽  
Arnhem Land

Allosyncarpia ternata S.T.Blake (Myrtaceae) is an evergreen tree, restricted largely to rocky habitats on the Arnhem Land Plateau in the wet–dry tropics of northern Australia. Allosyncarpia ternata grows in a wide range of habitats, including sites near permanent springs, where it forms a distinctive closed-canopy forest with an understorey of rainforest plants, and sites on exposed cliffs and hilltops, where it occurs in open forest and woodland. Leaf water relations differ markedly between these contrasting sites. During the dry season, trees at open sites show strong diurnal hysteresis in stomatal conductance (gs); afternoon depressions in gs coincide with regular afternoon increases in vapour pressure deficit. Pressure–volume analyses indicate that A. ternata maintains turgor down to leaf water potential values of about –2.8 MPa, close to the minimum experienced by hilltop leaves late in the dry season. By contrast, trees on the ravine floor, with year-round access to water, exhibit much smaller diurnal and seasonal variation in stomatal conductance and little seasonal variation in leaf water potential. It is concluded that this flexible response in leaf water relations to seasonally dry conditions is partly responsible for the ability of A. ternata to occupy and dominate the vegetation in such a wide variety of habitats. The near confinement of the species to the Arnhem Land Plateau is in part due to the water-holding capacity of the bedrock.

Effect of temperature and hydric conditions on blood pH in embryonic snapping turtles (Chelydra serpentina)

1990 ◽  
Vol 68 (1) ◽  
pp. 190-193 ◽  
Author(s):  
Geoffrey F. Birchard ◽  
Mary J. Packard ◽  
Gary C. Packard
Keyword(s):  
Partial Pressure ◽  
Water Potential ◽  
Pure Water ◽  
Effect Of Temperature ◽  
Chelydra Serpentina ◽  
Blood Samples ◽  
Ph Changes ◽  
Blood Ph ◽  
Snapping Turtles ◽  
Increasing Temperature

The effect of temperature on blood pH in embryonic snapping turtles (Chelydra serpentina) was examined to determine whether the blood pH changes in the same manner as the neutral pH of pure water. Eggs were incubated on moistened vermiculite (water potential of −150 or −950 kPa) at 26 or 27 °C. On day 59 of incubation, eggs were placed in individual containers and assigned to incubators set at temperatures between 18.5 and 30 °C. Blood samples were taken on day 60 of incubation. Blood pH of the embryos varied in a manner similar to that observed in adults of this species: blood pH declined with increasing temperature, with a slope of −0.021 pH/°C. The decrease of blood pH with increasing temperature may be accomplished passively, with blood CO2 partial pressure increasing as a result of greater metabolic production of CO2 while the diffusive excretion of this gas remains relatively constant. No effect of substrate water potential on blood pH was observed.

Modification of the hydric environment by eggs of snapping turtles (Chelydra serpentina)

1984 ◽  
Vol 62 (12) ◽  
pp. 2401-2403
Author(s):  
William H. N. Gutzke
Keyword(s):  
Water Potential ◽  
Chelydra Serpentina ◽  
Snapping Turtles

Flexible-shelled eggs of snapping turtles (Chelydra serpentina) incubated on a dry substrate in the laboratory lost sufficient water to cause the water potential of their environment to increase significantly. This modification of the hydric environment prevented eggs from becoming desiccated and demonstrated the capacity of reptilian eggs to modify their environment in such a manner as to enhance their likelihood of completing development.

NITROGEN TRANSFORMATIONS NEAR UREA IN SOIL WITH DIFFERENT WATER POTENTIALS

1988 ◽  
Vol 68 (3) ◽  
pp. 569-576 ◽  
Author(s):  
YADVINDER SINGH ◽  
E. G. BEAUCHAMP
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Incubation Period ◽  
Relative Rate ◽  
Soil Water Potential ◽  
Nitrification Inhibitor ◽  
Silt Loam ◽  
Nitrogen Transformations ◽  
Water Potentials ◽  
Initial Soil

Two laboratory incubation experiments were conducted to determine the effect of initial soil water potential on the transformation of urea in large granules to nitrite and nitrate. In the first experiment two soils varying in initial soil water potentials (− 70 and − 140 kPa) were incubated with 2 g urea granules with and without a nitrification inhibitor (dicyandiamide) at 15 °C for 35 d. Only a trace of [Formula: see text] accumulated in a Brookston clay (pH 6.0) during the transformation of urea in 2 g granules. Accumulation of [Formula: see text] was also small (4–6 μg N g−1) in Conestogo silt loam (pH 7.6). Incorporation of dicyandiamide (DCD) into the urea granule at 50 g kg−1 urea significantly reduced the accumulation of [Formula: see text] in this soil. The relative rate of nitrification in the absence of DCD at −140 kPa water potential was 63.5% of that at −70 kPa (average of two soils). DCD reduced the nitrification of urea in 2 g granules by 85% during the 35-d period. In the second experiment a uniform layer of 2 g urea was placed in the center of 20-cm-long cores of Conestogo silt loam with three initial water potentials (−35, −60 and −120 kPa) and the soil was incubated at 15 °C for 45 d. The rate of urea hydrolysis was lowest at −120 kPa and greatest at −35 kPa. Soil pH in the vicinity of the urea layer increased from 7.6 to 9.1 and [Formula: see text] concentration was greater than 3000 μg g−1 soil. There were no significant differences in pH or [Formula: see text] concentration with the three soil water potential treatments at the 10th day of the incubation period. But, in the latter part of the incubation period, pH and [Formula: see text] concentration decreased with increasing soil water potential due to a higher rate of nitrification. Diffusion of various N species including [Formula: see text] was probably greater with the highest water potential treatment. Only small quantities of [Formula: see text] accumulated during nitrification of urea – N. Nitrification of urea increased with increasing water potential. After 35 d of incubation, 19.3, 15.4 and 8.9% of the applied urea had apparently nitrified at −35, −60 and −120 kPa, respectively. Nitrifier activity was completely inhibited in the 0- to 2-cm zone near the urea layer for 35 days. Nitrifier activity increased from an initial level of 8.5 to 73 μg [Formula: see text] in the 3- to 7-cm zone over the 35-d period. Nitrifier activity also increased with increasing soil water potential. Key words: Urea transformation, nitrification, water potential, large granules, nitrifier activity, [Formula: see text] production

Photosynthesis Response of Sunlit and Shade Pepper (Capsicum annuum) Leaves at Different Positions in the Canopy Under Two Water Regimes

1994 ◽  
Vol 21 (3) ◽  
pp. 377 ◽  
Author(s):  
A Alvino ◽  
M Centritto ◽  
FD Lorenzi
Keyword(s):  
Water Potential ◽  
Capsicum Annuum ◽  
Leaf Water Potential ◽  
Co2 Exchange ◽  
Leaf Water ◽  
Predawn Leaf Water Potential ◽  
Water Regimes ◽  
Water Potentials ◽  
Sun And Shade ◽  
Shade Leaves

Pepper (Capsicum annuum L.) plants were grown in 1 m2 lysimeters under two different water regimes in order to investigate differences in the spatial arrangements of the leaves and to relate this to daily assimilation rates of leaves of the canopy. The control regime (well-watered (W) treatment) was irrigated whenever the accumulated 'A' pan evaporation reached 4 cm, whereas the water-stressed (S) treatment was watered whenever the predawn leaf water potential fell below -1 MPa. During the growing cycle, equal numbers of sun and shade leaves were chosen from the apical, middle and basal parts of the canopy, corresponding to groups of leaves of increasing age. The CO2 exchange rate (CER) was measured at 0830, 1230 and 1530 hours on 8 days along the crop cycle, on leaves in their natural inclination and orientation. Leaf water potentials were measured on apical leaves before dawn and concurrently with gas exchange measurements. Control plants maintained predawn leaf water potential at -0.3 MPa, but S plants reached values lower than -1.2 MPa. Midday leaf water potentials were about twice as low in the S plants as in the controls. Water stress reduced LA1 during the period of crop growth, and dry matter production at harvest. Stressed apical leaves appeared to reduce stress by changing their inclination. They were paraheliotropic around midday and diaheliotropic at 0830 and 1530 hours. The CER values of the S treatment were significantly lower than those of the W treatment in apical and middle leaves, whereas the CER of basal leaves did not differ in either treatments. In the S treatment, reduction in the CER values of sunlit apical leaves was more evident in the afternoon than at midday or early in the morning, whereas basal leaves were less affected by water than basal stress leaves if sunlit, and negligibly in shaded conditions.

The Adaptive Strategy for Overwintering by Hatchling Snapping Turtles (Chelydra serpentina)

2001 ◽  
Vol 35 (3) ◽  
pp. 514 ◽  
Author(s):  
Paul A. Sims ◽  
Gary C. Packard ◽  
Philip L. Chapman
Keyword(s):  
Adaptive Strategy ◽  
Chelydra Serpentina ◽  
Snapping Turtles

Seasonal Changes in the Water Relations of Eucalyptus behriana F. Muell. And E. microcarpa (Maiden) Maiden in the Field

1984 ◽  
Vol 32 (5) ◽  
pp. 495 ◽  
Author(s):  
BA Myers ◽  
TF Neales
Keyword(s):  
Water Potential ◽  
Water Relations ◽  
Rainfall Intensity ◽  
Field Measurements ◽  
Canopy Conductance ◽  
Laboratory Studies ◽  
Short Term ◽  
The Mean ◽  
Type Response ◽  
Vapour Pressure Difference

Field observations of some parameters of the water relations of the two eucalypt species E. behriana and E. microcarpa in dry sclerophyll, mallee and woodland vegetation were made at three sites from 1980 to 1983. The mean ( n = 519) water potential measured at dawn (Ψdawn) was -3.07± 0.01 MPa and fluctuated seasonally with rainfall intensity over the range -2.0 ± 0, 1 to -4.4 ± 0.1 MPa ( n = 30). Both species behaved similarly and some osmotic adjustment took place. Mean leaf conductance (gs) varied between 0.151 ± 0.006 and 0.003 ± 0.001 mol m-2 s-1 . Maximum daily values of gs were linearly related to Ψdawn as it fluctuated seasonally. The slope of this linear regression was not significantly different from that relating these values of gs and Ψ, when both were measured concurrently. There were thus no indications of a distinction between the responses of gs to long- and short-term fluctuations of Ψ or of a threshold-type response of gs to Ψ. Field measurements indicated that gs was decreased at high values of vapour pressure difference (Δe). In laboratory studies with seedlings of the two species gs decreased from 0.5 to 0.1 mol m-2 s-I as Δe increased from 0.5 to 3.0 kPa. Leaf and canopy conductance were the predominant plant determinants of transpiration rate (Er) in this type of vegetation which has the capacity to restrict Et via the effect of water potential (Ψ) on gs and also by the response of gs to Δe. Some of the water relations parameters of E. behriana indicated that this species was better able to withstand drought than was E microcarpa.

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