June 2009

Vines

“Vine” is a label for a particular growth habit of plants. How would you recognize a vine or describe it to someone who knows nothing about plants? Here are some images that show how a vine grows.

Vines start by creeping along the ground.	When vines find a tree or bush they climb upward.
Grape vine on the ground	Virginia creeper on a tree

Hemp vine sprawls and flowers

ADVANTAGES OF THE VINE GROWTH HABIT

Vines have an advantage over trees because they can put more energy into leaves, flowers, and fruit than into support tissue. Even woody vines, called lianas, start out as thin green stems that climb upward onto trees.

Vines cover all other plants after a hurricane

Not only do vines use other plants for support but they also grow especially fast when times are good. After major hurricanes they often dominate for years before fallen and broken trees recover and re-grow. And with the increased carbon dioxide associated with global warming, we project that vines will become relatively more abundant because they put little energy into support tissue. See page 1 of the Plant-Animal Mutualisms column for a review of how carbon dioxide is used in photosynthesis.

 A continuous blanket of Kudzu, Pueraria montana,

the foot-a-day vine or the vine that ate the south. 

In addition some of our most invasive non-native plants are vines. Kudzu and old-world climbing ferns reduce the diversity of our native plants because they grow over and shade native plants. Non-native vines dominate because they have no natural enemies. On a spectrum of key species from positive to negative, they are the worst of the worst.

 

VINES FIND A PLACE TO GROW UPWARD

You may recall from the April essay on trees that sedentary plants can grow more leaves and roots in good conditions. The same is true of vines. With no need for woody stems, vines can colonize large areas quickly. With roots in an initially good place, vines grow outward in several directions and produce more leaves in the sun.

Dense grape vines under slash pine	Virginia creeper in patchy sunlight

 

DIFFERENT WAYS TO CLIMB

If growing tips of vines encounter a bush or tree then the vines grow upward. Some vines use twining tendrils to grow upward and onto and over bushes and other vines. Check out this amazing video.

Tendrils of a vine search for support 

Other vines grow upward on the trunks of trees in two ways. Poison ivy attaches to tree trunks by aerial rootlets along the stem. Virginia creeper attaches by adhesive disks that form at the end of tendrils. Both species flower and fruit only when they reach full sunlight, usually in a tree-top.

Poison ivy’s Latin name is Rhus toxicodendron. The yellow oily exudate from the leaves causes contact dermatitis i.e., an itchy, oozy skin rash. Some people are even sensitive to the oils in the smoke generated if they burn the vine. And we do not recommend that you test what may be an urban myth and eat progressively more bits of leaves to develop a resistance to the toxicity. Even if true, the intense itching and blistering upon defecation might be awful!

Leaves of three, leave me be; Hairy rope, don’t be a dope; Berries white, take flight.

Poison ivy leaves and aerial rootlets	Poison ivy berries in sunny tree-top

 

 Virginia creeper’s Latin name is Parthenocissus
quinquefolia – with leaves of five you won’t get hives.

Virginia creeper is a seeker

It starts in a sun-dappled glade
Creeping in and out of the shade
‘til it encounters a tree
climbs up it, home free
In full sun it now has it made

Virginia creeper vine starting up a tree	Virginia creeper adhesive discs

 

COMMENSALISM, COMPETITION, & PARASITISM

Recall the short-hand for these three kinds of biological interaction.

Commensalism is + (advantage) for one species and 0 (no effect) for the other species. The short-hand for commensalisms is + / 0. Epiphytes, the plants discussed in the Lichens and Bromeliads column, are commensals. By far the majority of vines are commensals when they climb on a host bush or tree.

Competition is – (disadvantage) for one species and - (disadvantage) for the other species. The short-hand for competition is - / -. Some vines may get so luxuriant that they cover and compete for sunlight and space with the leaves of their host.  

Parasitism is + (advantage) for one species and – (disadvantage) for the other species. The short-hand for parasitism is + / -. A very few species of vine are parasites in all or part of their lives. 

STRANGLER FIG: A COMMENSAL VINE THAT BECOMES A COMPETITOR TREE

Strangler fig, Ficus aurea, is a native species that can start as an epiphytic commensal, become a commensal woody vine, and end up as a competitive tree. 

Strangler fig must start as an obligate (necessarily) epiphyte when it cannot germinate and grow in the ground. This is the case where there is dense shade on the ground in the middle of a tree island or where there is standing water on the ground in our cypress swamp. Its fruit (see Plant-Animals Mutualism I column for fig life history) is dispersed by birds. The defecated seeds germinate on a rough tree trunk, in litter trapped where a tree trunk splits, or among the “boots” left on the trunks of our cabbage palm. 

Epiphytic fig in boots of cabbage palm

At first, an epiphyte fig grows very slowly because it has limited water and nutrients. As a result, it is small with few leaves and has no negative effects on its host. 

 

 

 

 

 

Network of fig vines on host tree

As the fig grows larger it sends out aerial roots. When the roots reach the ground the fig can suddenly grow much faster. The reason is that much more water and nutrients are available in the ground. The fig has become a vine and develops a network of stems entwining the host.

With its roots in the ground, the fig vine can grow upward through the branches of its host and into its tree-top. It has become a tree. It competes with its host not only for water and nutrients below ground but also for sunlight and space above ground.

 

 

 

 

 

 

Fig tree covers rotting trunk of host tree		Large leaves of fig can eventually shade fine leaves of cypress
	So we see that “strangler fig” is an unfortunate common name because it does not strangle its host. Rather it grows larger and larger and its wide, dense leaves eventually completely shade and kill its host.

	Strangler fig stump
New aerial roots grow in the space where the host tree trunk decomposes. This can be seen in a cross section of a strangler fig that fell in a hurricane and was cut down. Note the cross section of multiple trunks that started as aerial roots.

	Strangler fig growing over Mayan ruins
Strangler fig can start its life on a tree, on a rock wall, on a stump, or in the ground if it is not too wet or not too shaded. It gets to all possible habitats because of wide dispersal of its seeds by birds.

PARASITIC DODDER VINES

Dodder seedling climbs up host stem

Dodder vines are parasites as soon as a seedling finds and starts to grow on a host. Experiments support the hypothesis that dodder seedlings find a host by smell and grow toward it. Different plants have different odors and even humans can smell some of them, like tomato. If a seedling dodder does not find a host it dies in about a week.

Two types of dodders grow in south Florida. One is in the morning glory family, four Cuscuta species, and the more common species is in the laurel family, Cassytha filiformis. They look similar because they have little or no chlorophyll and always lack leaves. They are an example of convergent evolution, where unrelated species come to look alike because of similar adaptations as parasites.  

 

← Love vine covering host shrubs. The orange color is due to near absence of green chlorophyll.

Close-up of dodder on host →

Parasitic dodder vines have haustoria that penetrate their host’s stem and absorb water and nutrients. This gives them one of their common names: the vampire vine sinks its fangs into its victim and starts to drink. If the dodder gets dense enough it can kill its host.

 

 

 

← The bumps on the dodder stem are the haustoria that penetrate the host stem.

Once a dodder reaches a host it loses connection to the ground. As a parasite it does not need leaves, chlorophyll, or roots.

 

 

If plants are like animals, in other ways than smelling and searching, then parasitic vines will be found to have parasites which have even smaller parasites. As the parasitologist Robert Hegner wrote about animals:

Big fleas have little fleas
On their backs to bite ‘em.
And little fleas have lesser fleas,
And so ad-infinitum.

REVIEW QUESTIONS
 

a. Our native fig, Ficus aurea, strangles its host.
b. Vines that start life on the ground can smell, search for, and find a host.
c. Most vines are commensals in that they have a + / 0 relation to their host.
d. Vines grow much faster than their hosts and are likely to grow even faster as carbon dioxide concentrations rise with global warming.