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Abstract Detail

Developmental and Structural Section

Ramsey , Adam Joseph [1], Edwards, Jacob Aaron [1], Williams, Joseph [2].

Comparative economics of pollen tube growth in two water lily species.

Pollen tube growth rate (PTGR) is an important determinant of male fitness in flowering plants and is controlled by the rate at which walls are constructed at the tube tip. PTGR can evolve by changing the wall production rate (WPR), or by changing the economy of tube construction (i.e. using more or less wall material for a given WPR). We compared the relationship between tube construction costs and growth rates in two water lilies, Nuphar advena (Nymphaeaceae) and Brasenia schreberi (Cabombaceae). For each species, single-donor pollinations were done on pairs of nearest-neighbor flowers and fixed in FAA either soon after pollen germination (time A), or 45 min later (time B). Lengths of 5 or 10 leading pollen tubes were measured for each carpel and mean PTGR calculated for each male over the 45 minute growth period between time A and B. For each time B flower, an adjacent carpel was embedded in glycol methacrylate, serial-sectioned, and stained with purified aniline blue. Cross-sectional circumferences (C) and wall thicknesses (W) were measured at 630x magnification. For each male, WPR was calculated as the average of individual (W) x (mean PTGR). Within the observed period, tubes of both species had grown primarily within substigmatic tissues. In B. schreberi, leading pollen tubes were near the base of the style 90 minutes after pollination, and mean + SE PTGR was 757.7 + 68 μm/h. In N. advena, leading pollen tubes had just entered the ovary 105 minutes after pollination and mean + SE PTGR was 916.0 + 51 μm/h. Despite the faster PTGR of N. advena, the volume of wall material produced per unit of growth was higher in N. advena than in B. schreberi (P = 0.0004). Consequently, WPR was higher in N. advena than in B. schreberi (7391 + 436 µm3/hr vs. 5420 + 582 µm3/hr, respectively; P = 0.0098). The scaling of WPR to PTGR is a measure of the economy of pollen tube growth: tubes with a low WPR to PTGR ratio are using less wall material to extend their tube tip at a given rate towards the egg. The two species differed in their WPR to PTGR ratios (8.91 + 0.26 in N. advena vs. 7.23 + 0.35 in B. schreberi). The pollen tubes of B. schreberi used less wall material to achieve similar growth rates, and therefore had a more economical growth pattern.

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Related Links:
Williams Lab Page

1 - University of Tennessee, Ecology and Evolutionary Biology, Knoxville, Tennessee, 37996
2 - University Of Tennessee, Department Of Ecology & Evolutionary Biology, 341 HESLER BUILDING, 1406 Circle Drive, KNOXVILLE, TN, 37996-1100, USA, 865/974-6202

Pollen tube
Cell Biology
cell wall
growth rate
life history.

Presentation Type: Poster:Posters for Sections
Session: P
Location: Eyrie/Boise Centre
Date: Monday, July 28th, 2014
Time: 5:30 PM
Number: PDS007
Abstract ID:594
Candidate for Awards:Katherine Esau Award,Developmental and Structural Section best poster

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