Download 12 Angiosperm Reproduction

Angiosperm Reproduction
Sexual characteristics of flowering plants
Lebel-Hardenack and Grant, 1997
Plants have sex chromosomes too!
XY in Silene
22XX
22XY
22XY meiosis
Active Y and X : autosome systems present.
V. Di Stilio, 1998. PhD dissertation.
Genome 41 (2): 141-147 (1997).
Angiosperm
life cycle
Angiosperm ovule
with mature female gametophyte
Patterns of
ovule
development:
Classical table
Are all
angiosperms
represented?
Gifford and Foster, 1988
Modular duplication of the female gametophyte
during angiosperm evolution
Cronk, 2009, after Friedman & Williams 2004
Modular Hypothesis of Female
Gametophyte Evolution
Male gametophyte: Pollen development
Mascarenhas, J.
Mature Pollen grain
Exine patterns
Novelties of the flowering plant pollen tube
In class discussion (bring paper!)
Fertilization times: short (black), moderate (gray), long (light gray)
Williams, JH 2008. PNAS105(32)
Photo by G. Bergamini-Mulcahy
Franklin-Tong 2002
Angiosperm Pollination
Female signal is lost after fertilization
Pollen tube enters wt ovule
Fertilized ovule rejects pollen
tube
Palanivelu, R., and Preuss, D. (2006). Distinct short-range ovule signals attract or repel
Arabidopsis thaliana pollen tubes in vitro. Bmc Plant Biology 6.
Pollen-tube guidance: Beacons from the female gametophyte
Torenia ovule with extruded embryo sac
Higashiyama et al. 2003, 2008
No laser Control!
!
Conclusion from Higashiyama studies:
One synergid cell is necessary and sufficient for pollen tube
attraction.
Green=synergid cell
Red=pollen tube
Pollen tube enters through synergid cell, which subsequently dies.
Sandaklie-Nikolova et al, 2007. Synergid Cell Death in Arabidopsis Is Triggered
following Direct Interaction with the Pollen Tube. Plant Phys 144: 1753.
Angiosperm Double Fertilization
A seed is a fertilized ovule
Schematic sketch of seed development in the model plant Arabidopsis.
Sundaresan V PNAS 2005;102:17887-17888
©2005 by National Academy of Sciences
Ovule Develops into a Seed and
Ovary Develops into a Fruit
•  Fruit functions to protect the seeds, provides nutrients to
developing seedlings, and aids in dispersal from the
parent plant.
See Cronk Table 6.3 for fruit types
Angiosperm diversity:
Is it the flowers or the fruits?
KD Whitney. Proc. Roy Soc B, 2009