☰ Contents · Botany

Dispersal of fruits and seeds, and germination

Lessons 34–35 · 2 lessons · O. Pratov, A. Tukhtaev, F. Azimova, I. Saparboev, M. Umaraliyeva. Biology (Botany), Grade 6. O‘zbekiston Publishing House, Tashkent, 2017
34

Dispersal of fruits and seeds

Textbook: pp. 83–84
GoalExplain the ways fruits and seeds are dispersed (by themselves, wind, water, animals, humans) with examples.
New words
self-dispersing plant (autochore) · avtoxor o‘simlikwinged fruit · qanotchali mevaplumes / fluff · tukchalar (popuk)dispersal · tarqalish
Explanation

Dispersal of fruits and seeds lets a species settle new places and get out of the parent’s shade. The method depends on fruit structure. Self-dispersers (autochores): balsam (xina), most legumes, vetch (burchoq), squirting cucumber (itqovun) — when the fruit ripens, internal pressure, splitting or twisting of the valves throws seeds out. Wind: fruits of poplar, willow, dandelion and cattail carry a tuft of light fluff at the tip and fly long distances; elm, ash, saksovul and maple have wings on their fruit. Water: fruits with waterproof coats (water lily, Johnson grass, plantain) float far away. Animals and birds: spiny, hooked or sticky fruits cling to wool and feathers; juicy fruits are eaten and indigestible stones and seeds are scattered with droppings. People are the most powerful disperser: in early in the 20th century camelthorn (yantoq) seed reached America mixed into lucerne seed from Central Asia. Dispersal lets plants occupy new land.

By itself(autochory)WindWaterAnimals andbirdsPeopleDispersal offruits and seeds
Worked examples
A dandelion fruit flies on light fluff — wind dispersal; a bird swallows a cherry and drops the stone far away — animal (bird) dispersal.
Elm and maple fruits have wings: they spin and land far from the parent in the wind. A squirting cucumber shoots out its seeds under pressure when ripe.
Class activity

“Dispersal analysis”: sort a dried collection of fruits and seeds (dandelion, maple wing, cherry stone, legume pod, spiny fruit) into groups: wind, water, animal, self. Experiment: drop a maple wing or dandelion fruit from a height and compare the falling time with a small wingless seed. Safety: handle spiny fruits carefully; do not taste unknown fruits; do not stand on a chair to drop things (the teacher drops them).

Practice
1
Name 3 wind-dispersed plants and their adaptation.
2
What are autochores? Give examples.
3
How do animals spread seeds?
4
Why is it useful for a plant’s seeds to spread far from the parent?