Abstract Detail



Time to dig: the importance of underground storage organs in plant evolution

Mocko, Kerri [1], Jones, Cynthia [2].

Functional leaf traits predict below-ground biomass in response to drought among morphologically diverse but closely related geophyte species.

For geophytes, accumulation of below-ground biomass is a critical component of species survival through unfavorable conditions. Geophyte diversity is high in Mediterranean regions where the ability to withstand hot, dry summers depends on tuber storage of water and carbohydrates. With prolonged leaflessness and reliance on storage, drought for geophytes during the time of maximum leaf functioning before deciduousness will likely have compounding effects on biomass accumulation and by extension survival past dormancy. Strategies of resource acquisition are predicted to link strongly to functional leaf traits by the Leaf Economics Spectrum, but we lack a direct test of whether these predictions hold for geophytes under well-watered and water-limited growing conditions, and how these leaf traits influence allocation to tubers. We ran an experimental dry-down extending over 9 days during peak growth on four geophytic species of Pelargonium. These four species exhibited a more than ten-fold difference in tuber and canopy size across species, but had identical root+tuber:shoot biomass ratios at the end of the season. Specifically we asked: do morphological traits or ecophysiology, or a combination of both, predict biomass under control conditions or in response to drought? Of all of the physiological variables we measured (leaf water potential, stomatal conductance, Amax, and leaf area), Amax had the strongest effect on tuber dry-weight biomass in the control plants. However, in those plants that experienced serious dry-down, tuber biomass was strongly and positively modulated by leaf size, and leaf size was directly, positively related to both LMA and Amax, which were also related to each other. This set of relationships was pronounced in response to drought. Interestingly, leaf number and rate of leaf loss and turnover had no effect on tuber biomass under either control or droughted conditions. These results suggest a strong role for leaf size in predicting tuber size when Pelargonium geophytes are challenged by short-term drought.


1 - California State University Fullerton, Biological Science, 800 N. State College Blvd., Fullerton, CA, 92831, United States
2 - University Of Connecticut, Department Of Ecology & Evolutionary Biology, Unit 3043, 75 N. Eagleville Rd., Storrs, CT, 06269, United States

Keywords:
drought
functional traits
photosynthesis
Leaf mass per area
South Africa
Pelargonium.

Presentation Type: Colloquium Presentations
Number: 0008
Abstract ID:1030
Candidate for Awards:None


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