Transcript Asexual reproduction

Plant Reproduciton
and Nutrient Needs
Basic Plant Science
AFNR-BAS-13: Explain and demonstrate basic plant science principles
including plant health, growth and reproduction.
Asexual Reproduction
 Asexual reproduction: producing new plants from
parts of a plant (leaves, stems, etc.)
 another name for plant reproduction is propagation
 propagation: deliberately controlling and
manipulating the reproduction of a plant
 new plants created through asexual reproduction
are identical to the parent plant
 genetic duplicates of parents are often called clones
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Asexual Reproduction
Methods
 Cuttings and Division/Separation
 Grafting
 Layering
 Tissue Culture (a.k.a. Micropropagation)
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Cuttings and
Separation/Divsion
 most common and simple methods of asexual
reproduction
 separation and division: splitting apart a root or root
system into two or more pieces which each become a
new plant
 (ex. hostas, potatoes, daylillies, ornamental grasses)
 cuttings: segments of leaves, stem, or roots are cut off
and then placed in growing media to develop into new
plants
 (ex. begonias, ivy, pothos, African violet, wandering Jew)
 usually plants that root easily are used and the cuttings
are treated with rooting hormone before being planted
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Grafting
 method commonly used on trees by orchards and
nurseries
 the upper part of one plant is joined to the lower
part of another so they grow as one plant
 (ex. apples, citrus, hibiscus)
 scion: the part of the graft that will become the stem
 rootstock: the lower portion of the graft that
includes the roots
 union: where the two grafts meet
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Layering
 part of a stem or tip that is still attached to the
parent plant is covered in soil or media until
adventitious roots form
 most successful on woody plants
 the parent plant provides water and nutrients to the
new plant until roots are formed
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Tissue Culture
 entire new plants are grown from small pieces of
plant tissue placed in in artificial media under
sterile conditions
 the media is a gel containing moisture, nutrients,
and hormones for plant growth
 used to make large populations of plants that are
genetically identical
 can be used to improve genetics quickly
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Advantages of Asexual
Reproduction
 keep best characteristics pure
 some plants are difficult to reproduce sexually
 shorten the time to produce a mature plant versus
starting from a seed
 can create large numbers of identical plants
 can reduce disease occurrence
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Disadvantages of Asexual
Reproduction
 the main disadvantage is the potential for impact on
biodiversity of a species
 also if a particular plant clone is susceptible to
certain diseases, there is potential to lose entire
crops
 can be more expensive and requires more skill
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Sexual Reproduction in Plants
 pollination: the transfer of pollen grains from the
male part of the flower (the anther) to the female
part (the stigma)
 self-pollination: on plants with complete flowers the
pollen falls from the anther onto its own stigma
 cross-pollination: plants that have incomplete
flowers (or have complete flowers but are not
compatible for self-pollination) require pollinators
to transfer the pollen to another plant
 common pollinators: wind, birds, insects, bats
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Flower Anatomy
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Plant Parts
 Flowers:
 complete flowers: flowers that have all the parts
(sepals, petals, stamen, and pistil)
 incomplete flowers: flowers that lack one of the four
main parts - petals, sepals, pistil, or stamen
 male flowers will not have a pistil and female flowers
will lack stamen
 monoecious: plants that have male and female flowers
on the same plant
 dioecious: plants that have male and female flowers
on separate plants
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Sexual Reproduction in Plants
 fertilization: when the male sex cell joins with the
female sex cell (the ovule)
 the pollen grain lands on the stigma and then grows
a tube down the style to the ovary to make a gamete
(a fertilized egg)
 the ovule expands and develops into the seed while
the petals and sepals fall off; most flowers have
many ovules and therefore develop many seeds
 in some plants, the ovary expands and develops
into the fruit or pods
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Sexual Reproduction in Plants
 germination: the process of a seed developing into a
plant
 seeds will remain dormant until the proper conditions
are met and these vary depending on the type of seed
 common germination variables are planting depth,
amount of moisture, and proper temperature
 scarification: wearing away the seed coat to allow water
in to the embryo
 stratification: cold treatment of seeds to simulate natural
winter conditions to promote germination
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Sexual Reproduction
Advantages
 seeds are easily stored from year to year and over a
long period of time
 an inexpensive way to grow a large number of
plants
 easy to do and usually does not require special skills
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Sexual Reproduction
Disadvantages
 offspring are genetically different from parents so
desirable traits can be lost or depleted
 germination rates can be low
 length of time to a mature plant can be long
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Nutrient Needs of Plants
 Carbon (C), Hydrogen (H), and Oxygen (O) are the
three elements plants obtain from the atmosphere
 used by plants for metabolic processes to make food
and break down stored sugars
 nutrients in the soil must be dissolved in water
before being absorbed through a plant's roots
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Nutrient Needs of Plants
 there are 16 or 17 essential nutrients needed by
plants in different amounts
 not always enough of these are in the soil for
healthy plant growth so we use fertilizers or
compost to add the nutrients to the soil
 deficiency: a shortage of a given nutrient needed by
a plant
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Nutrient Needs of Plants
 Macronutrients
 needed in the greatest amount by plants for maximum
growth
 Nitrogen (N), Phosphorous (P), and Potassium (K) are
the major nutrients usually lacking in the soil because
plants use large amounts for growth
 Calcium (Ca), Magnesium (Mg), and Sulfur (S) are
also major nutrients but are not usually needed when
fertilizing because there is enough in the soil
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Nutrient Needs of Plants
 Micronutrients
 elements essential for plant growth which are needed
in only very small quantities
 also known as trace elements
 Boron (B), Copper (Cu), Chlorine (Cl), Iron (Fe),
Manganese (Mn), Molybdenum (Mo), and Zinc (Zn)
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Nutrient Needs of Plants
 Fertilizers
 materials containing essential plant nutrients that are
added to the environment around the plant
 generally added to irrigation water or soil, but some
can also be added to the air or sprayed on plant leaves
 All fertilizers are labeled with three numbers giving
the percentage of nitrogen, phosphorus, and
potassium (N-P-K).
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Nutrient Needs of Plants
 Fertilizers
 Filler is also included and is important to evenly
spread the fertilizer and avoid burning plants with too
much fertilizer.
 The best fertilizer to use depends on many factors,
such as the nutrients needed, soil structure, soil
chemistry, and method of applying the fertilizer.
 Soil pH is one of the most important soil properties
that affects the availability of nutrients.
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Nutrient Needs of Plants
 Fertilizers
 organic fertilizers: the nutrients contained in the
product come from the remains or by-products of a
once-living organism
 examples: cottonseed meal, blood meal, bone meal,
hoof and horn meal, and all manures
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