Weeds L3 Flashcards
Weed biology
part of weed science devoted to the study of the growth, development, and reproduction of weeds
Why do we need weed biology
essential for developing effective control methods
need to identify weed to control it
allows us to minimize negative effects
most effect weed control methods are based on the _____ _______
life cycle
control methods vary depending on:
weeds species, crop, field situation, environmental conditions
Aspects of weed biology that affect weed management
life stages/cycles
emergence periods
fecundity (seed production)
seed longevity
risk of developing herbicide resistance
What 2 parts indicate the potential weed problem
seed longevity and seed production
4 stages of weed development
seedling
vegetative
seed production
maturity
seedling stage
small, delicate, newly emerged plants
vegetative stage
fast growth; production of stems, roots, and leaves
seed production stage
energy is directed towards seed production
maturity
seed shed and plant death
seeds vs. seedlings
Seeds are not easy to detect but seedlings are
seeds can disperse easily, but seedlings cant move
Seeds can persist in soil but seedlings are weak/die easily
Seeds are physically and chemically defended but seedling are vulnerable
Types of weed reproducton
Sexual (seeds)
asexual (specialized vegetative structures
asexual seeds (apomixis)
sexual reprodcution
requires fertilization of an egg by sperm to produce chance for genetic change
can vary greatly among and within weed species
(less important for perennials)
Weeds generally produce _____ seeds than crops
more
Example of genetic change in weeds
herbicide resistance
Asexual reproduction via seeds
apomixis which uses no miosis or fertilization. Apomixis seeds are genetic clones of their mothers
examples of weeds reproducing via apomixis
hawkweed, dandelion
how many angiosperms can reproduce via apomixis
over 400 (most can also reproduce sexually)
Asexual reproduction via specialized vegetative structure
new plant develops from a modified stem, root, or leaf
common in perennial and can be just as successful as seeds
examples of vegetative structures
rhizomes (underground stems)
stolons/runners (above-ground stems)
bulbs, corms, and tubers
vegetative reproduction weed example
common chickweed (stolon)
Canada thistle (rhizomes)
nutsedge (tubers)
benefits of dispersal for the weed
colonization of new or more suitable habitat
reduction of parent-offspring competition
make sure offspring are spread out to avoid attracting predators (Jazen-Connell hypothesis)
reduction in inbreeding
Dispersal by wind
weed seeds and fruits that disseminate through wind that have special organs to keep them afloat