Abstract Detail

Physiology & Ecophysiology

McMann, Natalie [1], Savage, Jessica [2].

Flowering without leaves: Does stem hydraulic supply constrain floral water loss?

Tree species in temperate zones experience winter temperatures low enough to compromise the integrity of their xylem. Paradoxically, several of these species (e.g. aspen, elm, or red maple) flower early in the spring when freezing temperatures may still occur. They also exhibit precocious flowering, meaning they are capable of flowering before they put out leaves. I am investigating two possible strategies that could allow flowering under conditions when hydraulic capacity might limit access to water. First, water loss from the flowers may match the hydraulic capacity of the branch bearing them, indicating that flowering may be constrained in terms of timing, floral size, or water use by branch hydraulic capacity. Second, floral water loss may be substantially less than the branch hydraulic capacity and thus water supply does not constrain flowering. To test these mechanisms, I measured the floral water loss and branch hydraulic capacity of six precocious flowering species exhibiting a wide range of floral sizes and morphology. I used a LICOR 6400 conifer chamber to measure the evaporative water loss from floral structures during full bloom. I then measured stem hydraulic conductance by flowing partially degassed solution gravimetrically through a stem segment and recording the flow rate with a Sensirion liquid flow sensor. The stem segment was excised from the same branch that I used to determine evaporative water loss. Preliminary results show that floral size positively correlates with floral water loss. Across all species, the data also show that flowers, on a branch basis, are not constrained by hydraulic supply. Furthermore, flowers appear to lose less water than leaves based on a comparison in four species of floral water loss to leaf evapotranspiration on a branch basis.

1 - University of Minnesota-Duluth, Biology , 207 Swenson Science Building, 1035 Kirby Drive, Duluth, MN, 5812, USA
2 - University Of Minnesota - Duluth, Biology, 1035 Kirby Drive, 207 Swenson Science Buildling, Duluth, MN, 55812, United States

xylem hydraulics
stem hydraulics
Temperate trees
Woody Plants.

Presentation Type: Poster
Number: PPE004
Abstract ID:476
Candidate for Awards:None

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