Lecture 10-12Aquatic Macrophytes.pdf

Plant phylogenetic tree

The life cycle of 

a moss

sporophyte 

Sphagnum, a 

common 

wetland moss 

protoneme 

Spongy rhizoid 

tissue 

http://images.google.ca/imgres?imgurl=http://kentsimmons.uwinnipeg.ca/2152/l8fig4.jpg&imgrefurl=http://kentsimmons.uwinnip 

eg.ca/2152/lb8pg1.htm&h=664&w=600&sz=146&hl=en&start=2&tbnid=Jh_EsdcGnUOr6M:&tbnh=138&tbnw=125&prev=/imag 

es%3Fq%3DSphagnum%2Blife%2Bcycle%26svnum%3D10%26hl%3Den%26lr%3D%26sa%3DN

antheridium 

Antheridia clusters on the 

leaf tips of gametophyte 

archegonium 

Parasitic 

sporophyte

Fontilalis antipyretica 

Habitat: Water moss is found attached to rocks or logs in swift flowing water, or floating loose or 

attached to substrate in still water. It is common in shaded sites and prefers slightly acidic water. 

It requires water below pH 8.4 where dissolved carbon dioxide is available.

Most ferns are homosporous—only one kind of spore and gametophyte 

bears both sexes at different times 

Fig. 29.23

Salvinia spp: a floating aquatic fern: aggressive weeds in shallow standing waters or slow 

moving streams 

Most species polyploid and sporangia are sterile 

Reproduction: Salvinia molesta effectively reproduces through vegetative means. Stems fragment spontaneously 

as plants mature. New branches develop from apical and lateral buds. Each node harbors up to five serial lateral 

buds (Lemon and Posluszny 1997), adding to the high potential for growth and dormancy. Salvinia molesta will 

withstand periods of stress, both low temperature and dewatering, through latent buds. 

http://images.google.ca/imgres?imgurl=http://www.botgard.ucla.edu/html/botanytextbooks/lifeforms/images/aquaticplants/Salvinia1 

.jpg&imgrefurl=http://www.botgard.ucla.edu/html/botanytextbooks/lifeforms/aquaticplants/a0042tx.html&h=239&w=360&sz=24&hl=en 

&start=4&tbnid=Jm4d6m082X6MxM:&tbnh=80&tbnw=121&prev=/images%3Fq%3Daquatic%2Bfern%26svnum%3D10%26hl%3Den 

%26lr%3D%26sa%3DG

Azolla, an aquatic fern used in rice culture 

Is this plant homo- or 

heterosporous?

Phylum Pterophyta—sporophytes are vascular 

plants with megaphylls—ferns, horsetails, etc. 

Phylum Pterophyta 

The sphenophytes 

Equisetum—the horsetail 

•Upright jointed stems 

growing from a rhizome 

•Reproductive and 

vegetative stems separate 

Left—reproductive stems 

bearing strobilae 

Right—vegetative stems

Strobila of Equisetum with sporophylls 

bearing sporangia

The life cycle 

of Equisetum 

A 

homosporous 

cycle

Isoetes, the quillwort

http://www.cartage.org.lb/en/themes/sciences/BotanicalSciences/ClassificationPlants/Cryptogamia/Bryophyta 

/NonvascularPlants/NonvascularPlants.htm 

Heterospory 

Some ferns 

Quillwort 

Seed plants 

Advantages and disadvantages? 

Trade-offs? 

Homospory 

Most ferns 

Horsetails

Life-cycle stages of a flowering plant

The anther is a 

microsporangium, and 

the pollen grain is a 

microspore that 

germinates to form the 

male gametophyte (2 

cells) 

The megaspore is 

inside the ovule, and 

becomes an 8-celled 

gametophyte 

Fig. 30.13a

he 

evelopment of 

ngiosperm 

ametophytes 

Fig. 38.4

Although plants evolved from algal ancestors, the shift from water to air as a 

medium has resulted in major adaptative changes in structure and function 

Algae 

•essentially weightless and lack supporting tissue 

•no water or nutrient transport, 

•Take up nutrients through the body surface from the surrounding water 

•Use only holdfast cells for anchorage 

•Most cells can photosynthesize and they have no need for stomates or an 

impermeable cuticle 

•Gametes swim through water 

Terrestrial plants have gradually evolved 

•roots for anchorage, water and nutrient uptake 

•vascular tissue for water and nutrient transport, and tensile strength 

•Leaves with concentrated photosynthetic tissue, a waxy cuticle and stomates to 

regulate gas intake and water loss 

•Mechanisms to protect gametes from drying, 

•Pollination mechanisms to bring gametes together

With the exception of brypohytes which have always been heavily 

dependent on water, aquatic plants are mostly flowering plants that have 

evolved from terrestrial plants and retain many of their features 

Key terrestrial plant adaptations that aquatic plants retain: 

•most have roots or rhizomes that anchor the plant and take up nutrients 

•most have true leaves, supplied by vascular tissue (veins) and have vascular tissue 

in their roots & stems 

•most reproduce sexually through flowers that produce pollen and seeds

Aquatic flowering plants, although retaining fundamental features that reflect 

their terrestrial history, have evolved many adaptations for life in water. 

They don’t however revert back to their ancestral algal body plan. 

Root adaptations 

•Reduction in roots, since water uptake is not necessary, some lack roots or rhizomes 

•Tolerance of hypoxia—pumping O 2 to rhizomes and roots (aerenchyma) and tolerating 

elevated ethanol or ethylene 

Stem adaptatons 

•Lacunate tissue—spongy air-filled tissue in roots and stems 

•Reduction of xylem tissue—less need for support or water transport, combined with 

increased flexibility, substituting tensile strength for rigidity 

Leaf adaptations 

•Stomata greatly reduced or absent, cuticle very much reduced 

•Epidermis well supplied with chlorophyll 

•Thin or finely dissected leaves, to provide high surface/mass 

Reproductive adaptations 

•Flower reduction--pollination usually by water or wind, and rarely insects 

•Fruit modification--spongy tissue (floating) for dispersal by water 

•Increased reliance on vegetative propagation—fragmentation (winter buds) or 

suckering 

Overall aquatic plants remain imperfectly adapted to life in water

Common Cattail 

Typha latifolia 

Cattail family (Typhaceae) 

Spike bearing staminate flowers 

Each staminate flower bears grains of pollen; its 

petals and sepals are reduced to bristles. After the 

pollen is released, the staminate spike quickly 

withers away. 

Spike or catkin carrying pistillate 

flowers 

fertile pistillate flower has a stipe at least 1 mm. long, 

a single achene, and a single style with a flattened 

stigma. The pistillate spike persists into the fall. 

The blooming period occurs during early to midsummer. 

The root system produces thick starchy 

rhizomes and fibrous roots. Colonies often grow and 

expand vegetatively when new shoots are produced 

from the starchy rhizome.

Typha latifolia

http://www.tva.gov/river/landandshore/stabilization/plants/images/scirpus_americanus.jpg 

Bulrush—scirpus americanus 

Stem green, hollow, spongy, leaves few and small 

Well developed rhizomes, flowers small brown 

http://cricket.biol.sc.edu/herb/SS/Scirpus_americanus1.jpg

Scirpus microcarpus: panicled bulrush

agittaria latifolia, broad-leafed arrowhead 

Well-rooted in mud 

along shores of lakes 

or ponds 

http://www.uwgb.edu/BIODIVERSITY/herbarium/wetland_plants 

Flowers quite showy for an 

aquatic plant 

Incomplete 

i.e. pistillate or staminate

The white water lily Nymphaea 

Leaves floating only 

Well-rooted—thick air-filled rhizome 

http://images.google.ca/imgres?imgurl=http://www.ontariowildflower.com/images/bulrushhardstem.jpg&imgrefurl=http://ww 

w.ontariowildflower.com/lakes.htm&h=483&w=370&sz=11&hl=en&start=5&tbnid=fPRsJ194C3ZH3M:&tbnh=129&tbnw=99 

&prev=/images%3Fq%3Dbulrush%2Bflower%26svnum%3D10%26hl%3Den%26lr%3D%26sa%3DG

Nuphar variegata: bull-head pond lily 

Leaves floating only 

Well-rooted—thick air-filled rhizome 

http://www.uwgb.edu/BIODIVERSITY/herbarium/wetland_plants

The smartweed Polygonum 

Well rooted, floating leaves ovate, 

submerged leaves thinner

Common duckweed: Lemma minor 

Non rooted, floating rhizomatous leaves 

Lemma trisulca 

http://images.google.ca/imgres?imgurl=http://www.mobot.org/jwcross/duckweed/graphics/frog_in_duckweed.gif&imgrefurl=http:// 

www.mobot.org/jwcross/duckweed/duckweedcharms.htm&h=291&w=432&sz=122&hl=en&start=1&tbnid=SyVvY42awRVryM:&tbnh=85&tbnw=126&prev=/images%3Fq%3DD 

uckweed%26svnum%3D10%26hl%3Den%26lr%3D%26sa%3DG

Floating leaved Pondweed, Potamogeton natans 

•Floating leaves ovate, 

• submerged leaves 

grass-like 

•Well rooted

Water milfoil, Myriophyllum exalbescens 

Finely 

dissected 

leaves

Potamogeton filiformis 

Thin fine filiform leaves, very flexible plant, well adapted for current and wave action

Potamogeton praelongus 

Large leaves, well rooted plant 

http://images.google.ca/imgres?imgurl=http://www.uwgb.edu/BIODIVERSITY/herbarium/wetland_plants/potpra_FlowersAndFruit01gf 

400.jpg&imgrefurl=http://www.uwgb.edu/BIODIVERSITY/herbarium/wetland_plants/potpra01.htm&h=400&w=224&sz=17&hl=en&star 

t=15&tbnid=61554dy6xY2IiM:&tbnh=124&tbnw=69&prev=/images%3Fq%3Dpotamogeton%2Bflower%26ndsp%3D20%26svnum%3 

D10%26hl%3Den%26lr%3D%26sa%3DN

Vallisneria americana 

http://www.uwgb.edu/BIODIVERSITY/herbarium/wetland_plants/valame_aspect01_web400gf.jpg

Vallisneria americana: a dioecious species, sexes on separate plants 

Flowers open at the water’s surface—wind pollinated Staminate plant 

Pistillate plant 

Also capable of asexual reproduction through vegetative “suckering” 

Leaves highly flexible, well adapted for high wave action

Utricularia vulgaris: common bladderwort 


Potamogeton richardsoni 


Potamogeton amplifolius, big-leafed pondweed 

Large leaves, well rooted plant 


Elodea canadensis 

Roots very reduced, stems thin fragment easily 

Flowers very small, on long stems that reach the 

surface 

Wind pollinated 


Ceratophyllum demersum: coonstail 

Finely dissected leaves 

Small spikes on leaves 

No roots or underground rhizome 

No flowering— reproduces by 

asexual fragmentation

Lecture 10-12Aquatic Macrophytes.pdf

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