BIOA02H3 Lecture Notes - Lecture 9: Sex Organ, Outcrossing, Flowering Plant
27 Apr 2018
School
Department
Course
Professor
BIO A02 – Module 1 Notes Hassan Alibhai
Plant Form and Function Page 40
Self Incompatibility
•The plant is able to biochemically recognize
that it is attempting to fertilize with pollen of
its own DNA => “self-pollen” is rejected
◦To avoid this, the stigmatic surface
underneath the self-pollen is effectively
“closed”, and it cannot undergo fusion
being barred access to the ovule and style
◦Outcross (or outbreeded) pollen has no
problem doing this, of course
Roles of Flower Genders
•Temporal and spatial separation (of genders) was later researched to actually ease the efficiency
of pollen pickup and delivery instead of focus on avoidance of selfing.
◦Male sexual anatomy activated => pollen is produced much faster
◦Female sexual anatomy activated => pollen is received and transferred much faster
•Self-incompatibility is therefore the form of ultimate selfing avoidance.
Temporal Separation Spatial Separation Self-incompatibility
•Male and female
reproductive organs
activated at different
times of the day
•Male and female
reproductive organs
spaced out so as not to
interact physically
•Angiosperm is unable to
reproduce with the same
genetic material of the
same flower
•Intra-flower (between genders of the same flower)
•Pollen pickup and delivery is made more efficient
•Inter-flower (2 flowers)
•Self-fertilization avoided
The Success of Angiosperms- Forces Behind the Evolution of Flowers
•Extreme diversity in the types of flowers produced
◦275 000 + angiosperms, next closest category is sperms, which come in at 12 000+
•Two main forces
Assurance of seed set => two parents
always replaced by gametes (mechanics)
Inbreeding avoidance, primarily due to
self-incompatibility and a bit of separation
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BIOA02H3 Full Course Notes
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