Limits...
Floral Mass per Area and Water Maintenance Traits Are Correlated with Floral Longevity in Paphiopedilum (Orchidaceae)

View Article: PubMed Central - PubMed

ABSTRACT

Floral longevity (FL) determines the balance between pollination success and flower maintenance. While a longer floral duration enhances the ability of plants to attract pollinators, it can be detrimental if it negatively affects overall plant fitness. Longer-lived leaves display a positive correlation with their dry mass per unit area, which influences leaf construction costs and physiological functions. However, little is known about the association among FL and floral dry mass per unit area (FMA) and water maintenance traits. We investigated whether increased FL might incur similar costs. Our assessment of 11 species of Paphiopedilum (slipper orchids) considered the impact of FMA and flower water-maintenance characteristics on FL. We found a positive relationship between FL and FMA. Floral longevity showed significant correlations with osmotic potential at the turgor loss and bulk modulus of elasticity but not with FA. Neither the size nor the mass per area was correlated between leaves and flowers, indicating that flower and leaf economic traits evolved independently. Therefore, our findings demonstrate a clear relationship between FL and the capacity to maintain water status in the flower. These economic constraints also indicate that extending the flower life span can have a high physiological cost in Paphiopedilum.

No MeSH data available.


The typical pressure–volume curve of Paphiopedilum (here depicted by P. malipoense). Low values of both water potential and RWC were obtained from the very start of the experiment because water potential was measured with a WP4 Dewpoint Potentiometer, which determines the relative humidity of the air above a flower sample in a closed chamber. Thus, species flower turgor loss points are likely more negative than if flower water potential had been measured with a pressure chamber.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5383722&req=5

Figure 2: The typical pressure–volume curve of Paphiopedilum (here depicted by P. malipoense). Low values of both water potential and RWC were obtained from the very start of the experiment because water potential was measured with a WP4 Dewpoint Potentiometer, which determines the relative humidity of the air above a flower sample in a closed chamber. Thus, species flower turgor loss points are likely more negative than if flower water potential had been measured with a pressure chamber.

Mentions: Mature flowers were quickly sampled from five or six plants per species early in the morning, sealed in plastic bags, and immediately transported to the laboratory. After the scapes were re-cut under water, these flowers were soaked in deionized water for 12 h to achieve full hydration, and they were weighed to obtain their saturated fresh weights (FWs). The samples were then cut into segments in a plastic bag with damp paper towel to prevent dehydration by transpiration in air and rapidly placed in individual chambers (diameter 3.7 cm) for the WP4 Dewpoint Potentiometer (Decagon Devices, Inc., Pullman, WA, USA). After equilibration for approximately 30 s, the flower water potentials were recorded before FWs were measured to the nearest 0.0001 g on a digital balance. Water potentials and FW were determined periodically until those values stabilized. The samples were then oven-dried at 70°C for 24 h to obtain DW, and relative water content (RWC) was calculated as (FW-DW)/(FWs-DW). Pressure–volume curves (Figure 2) were obtained by plotting the inverse of water potential against RWC. The WP4 Dewpoint Potentiometer measures water potential by determining the relative humidity of the air above a sample in a closed chamber, thus the inability to get more hydrated values, so that the first point has low water potential and RWC (Figure 2). Turgor loss point was determined as the point of transition between linear and non-linear portions of the curve. Osmotic potential at the turgor loss point (πtlp) and relative water content at this point (RWCtlp) were also recorded accordingly (Tyree and Hammel, 1972). Osmotic potential at full turgor (πft) was estimated by extrapolating the linear portion of the curve to 100% RWC, and relative water content at full turgor (RWCft) was estimated by extrapolating the line to zero osmotic potential. Then the bulk modulus of elasticity (ε) was calculated as (πft-πtlp) × (RWCft – RWCtlp)/RWCft.


Floral Mass per Area and Water Maintenance Traits Are Correlated with Floral Longevity in Paphiopedilum (Orchidaceae)
The typical pressure–volume curve of Paphiopedilum (here depicted by P. malipoense). Low values of both water potential and RWC were obtained from the very start of the experiment because water potential was measured with a WP4 Dewpoint Potentiometer, which determines the relative humidity of the air above a flower sample in a closed chamber. Thus, species flower turgor loss points are likely more negative than if flower water potential had been measured with a pressure chamber.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5383722&req=5

Figure 2: The typical pressure–volume curve of Paphiopedilum (here depicted by P. malipoense). Low values of both water potential and RWC were obtained from the very start of the experiment because water potential was measured with a WP4 Dewpoint Potentiometer, which determines the relative humidity of the air above a flower sample in a closed chamber. Thus, species flower turgor loss points are likely more negative than if flower water potential had been measured with a pressure chamber.
Mentions: Mature flowers were quickly sampled from five or six plants per species early in the morning, sealed in plastic bags, and immediately transported to the laboratory. After the scapes were re-cut under water, these flowers were soaked in deionized water for 12 h to achieve full hydration, and they were weighed to obtain their saturated fresh weights (FWs). The samples were then cut into segments in a plastic bag with damp paper towel to prevent dehydration by transpiration in air and rapidly placed in individual chambers (diameter 3.7 cm) for the WP4 Dewpoint Potentiometer (Decagon Devices, Inc., Pullman, WA, USA). After equilibration for approximately 30 s, the flower water potentials were recorded before FWs were measured to the nearest 0.0001 g on a digital balance. Water potentials and FW were determined periodically until those values stabilized. The samples were then oven-dried at 70°C for 24 h to obtain DW, and relative water content (RWC) was calculated as (FW-DW)/(FWs-DW). Pressure–volume curves (Figure 2) were obtained by plotting the inverse of water potential against RWC. The WP4 Dewpoint Potentiometer measures water potential by determining the relative humidity of the air above a sample in a closed chamber, thus the inability to get more hydrated values, so that the first point has low water potential and RWC (Figure 2). Turgor loss point was determined as the point of transition between linear and non-linear portions of the curve. Osmotic potential at the turgor loss point (πtlp) and relative water content at this point (RWCtlp) were also recorded accordingly (Tyree and Hammel, 1972). Osmotic potential at full turgor (πft) was estimated by extrapolating the linear portion of the curve to 100% RWC, and relative water content at full turgor (RWCft) was estimated by extrapolating the line to zero osmotic potential. Then the bulk modulus of elasticity (ε) was calculated as (πft-πtlp) × (RWCft – RWCtlp)/RWCft.

View Article: PubMed Central - PubMed

ABSTRACT

Floral longevity (FL) determines the balance between pollination success and flower maintenance. While a longer floral duration enhances the ability of plants to attract pollinators, it can be detrimental if it negatively affects overall plant fitness. Longer-lived leaves display a positive correlation with their dry mass per unit area, which influences leaf construction costs and physiological functions. However, little is known about the association among FL and floral dry mass per unit area (FMA) and water maintenance traits. We investigated whether increased FL might incur similar costs. Our assessment of 11 species of Paphiopedilum (slipper orchids) considered the impact of FMA and flower water-maintenance characteristics on FL. We found a positive relationship between FL and FMA. Floral longevity showed significant correlations with osmotic potential at the turgor loss and bulk modulus of elasticity but not with FA. Neither the size nor the mass per area was correlated between leaves and flowers, indicating that flower and leaf economic traits evolved independently. Therefore, our findings demonstrate a clear relationship between FL and the capacity to maintain water status in the flower. These economic constraints also indicate that extending the flower life span can have a high physiological cost in Paphiopedilum.

No MeSH data available.