How can plants defend themselves?

Answer 1

Some plants use thorns to protect themselves from the environment. Some plants, like poison oak, release toxins to protect themselves. Some plants camouflage to hide themselves from predators. Some plants have poisonous fruit. Some plants have tough bark which protects themselves. The redwood tree, for example, has so much tannin in its bark that insects won't eat it. This is why you find very few insects in redwood forests.

Answer 2

Plants actually can't defend themselves. Some plants may have poison that help them from being eaten, but plants, by themselves, cannot defend themselves. There are carnivorous plants that eat other small predators, though, but that is not really self-defense.

Answer 3

Plant Adaptations

Ephemeral Leaves - leaves lasting a markedly brief time, sometimes only a day. Found in very dry climates that have a very short rainy season, like the desert.

Xerophyte - A plant adapted to living in a dry arid habitat; a desert plant.

Mesophyte - A land plant that grows in an environment having a moderate amount of moisture.

Hydrophyte - A plant adapted to grow in water.

Pleating - Edges of a plant arranged in parallel folds (ex. Ocotillo cactus).

Pubescence - A covering of short hairs on certain plants; usually found on desert plants.

Secondary Metabolites - compounds made by plants as a form of defense against predators. There are six classes - alkaloids, cyanogenic glycosides, saponins, cardiac glycosides, tannins and phenolics.

Convergent Evolution - The adaptive evolution of superficially similar structures, such as cacti and euphorbs (Africa), in unrelated species subjected to similar environments.

A cactus (left) and two Euphorbia species from Africa (center and right)

Adaptations develop over time and generations as a response to the ever changing environment. They allow an organism to reduce competition for space and nutrients, reduce predation and increase reproduction. There are however, several factors that can limit these adaptations: availability of water, light, predation and temperature. Because we live in a desert, this lab will focus mainly on the adaptations to a xeric environment.

Desert plants have adapted to the extremes of heat and aridity by using both physical and behavioral mechanisms, much like desert animals.

Plants that have adapted by altering their physical structure are called xerophytes. Xerophytes, such as cacti, usually have special means of storing and conserving water. They often have few or no leaves, thus reducing the amount of transpiration.

Phreatophytes are plants that have adapted to arid environments by growing extremely long roots, allowing them to acquire moisture at or near the water table. The term, phreatophyte, literally means water-loving plant.

Other desert plants, using behavioral adaptations, have developed a lifestyle patterned after the seasons of greatest moisture and/or coolest temperatures. These types of plants are usually (and inaccurately) referred to as perennials, plants that live for several years, and annuals, plants that live for only a season.

Desert perennials often survive by remaining dormant during dry periods of the year, then springing to life when water becomes available.

Most annual desert plants germinate only after heavy seasonal rain, then complete their reproductive cycle very quickly. They bloom prodigiously for a few weeks in the spring, accounting for most of the annual wildflower explosions of the deserts. Their heat- and drought-resistant seeds remain dormant in the soil until the next year's annual rains.

XerophytesThe physical and behavioral adaptations of desert plants are as numerous and innovative as those of desert animals. Xerophytes, plants that have altered their physical structure to survive extreme heat and lack of water, are the largest group of such plants living in the deserts of the American Southwest.

Cacti are among the most drought-resistant plants on the planet due to their absence of leaves, shallow root systems, ability to store water in their stems, spines for shade and waxy skin to seal in moisture. Cacti originated in the West Indies and migrated to many parts of the New World, populating the deserts of the Southwest with hundreds of varieties.

Barrel Cactus Opuntia Cactus Saguaro Cactus Cholla Cactus

Cacti depend on chlorophyll in the outer tissue of their skin and stems to conduct photosynthesis for the manufacture of food. Spines protect the plant from animals, shade the plant from the sun and also collect moisture. Extensive shallow root systems are usually radial, allowing for the quick acquisition of large quantities of water when it rains. Because they store water in the core of both stems and roots, cacti are well-suited to dry climates and can survive years of drought on the water collected from a single rainfall.

Many other desert trees and shrubs have also adapted by eliminating leaves -- replacing them with thorns, not spines -- or by greatly reducing leaf size to eliminate transpiration. Such plants also usually have smooth, green bark on stems and trunks serving to both produce food and seal in moisture, such as the Paloverde. Some plants produce ephemeral leaves during the brief rainy season to help increase transpiration and photosynthesis. Sometimes these leaves only last for one day.

PhreatophytesPhreatophytes, like the Mesquite Tree, have adapted to desert conditions by developing extremely long root systems to draw water from deep underground water tables. The mesquite's roots are considered the longest of any desert plant and have been recorded as long as 80 feet.

The Creosote Bush is one of the most successful of all desert species because it utilizes a combination of many adaptations. Instead of thorns, it relies for protection on a smell and taste wildlife find unpleasant (secondary metabolites). It has tiny leaves that close their stomata (pores) during the day to avoid water loss and open them at night to absorb moisture. Creosote has an extensive double root system -- both radial and deep -- to accumulate water from both surface and underground water.

PerennialsSome perennials, such as the Ocotillo, survive by becoming dormant during dry periods, then springing to life when water becomes available. After rain falls, the Ocotillo quickly grows a new suit of leaves to photosynthesise food. Flowers bloom within a few weeks, and when seeds become ripe and fall, the Ocotillo loses its leaves again and re-enters dormancy. This process may occur as many as five times a year. The Ocotillo also has a waxy coating on stems which serves to seal in moisture during periods of dormancy. Annuals (Ephemerals)The term "annuals" implies blooming yearly, but since this is not always the case, desert annuals are more accurately referred to as "ephemerals." Many of them can complete an entire life cycle in a matter of months, some in just weeks.

Contrary to the idea that deserts are uniformly hot, dry and homogeneous in their lack of plant life, they are actually biologically diverse and comprise a multitude of micro-climates changing from year to year. Each season's unique precipitation pattern falls on a huge variety of mini-environments. And each year in each of these tiny eco-niches, a different medley of plants bloom as different species thrive.

Desert plants must act quickly when heat, moisture and light inform them it's time to bloom. Ephemerals are the sprinters of the plant world, sending flower stalks jetting out in a few days. The peak of this bloom may last for just days or many weeks, depending on the weather and difference in elevation. The higher one goes, the later blooms come. Different varieties of plants will be in bloom from day to day, and even hour to hour, since some open early and others later in the day.

Ephemerals such as the Desert Paintbrush usually germinate in the spring following winter rains. They grow quickly, flower and produce seeds before dying and scattering their progeny to the desert floor. These seeds are extremely hardy. They remain dormant, resisting drought and heat, until the following spring -- sometimes 2 or 3 springs -- when they repeat the cycle, germinating after winter rains to bloom again in the spring. There are hundreds of species of ephemerals that thrive in the deserts of the American South west.

One plant adaptation important to the survival and early dominance of flowering plants is the production of secondary plant metabolites. These bad tasting and sometimes toxic compounds have been one of plants most powerful means of defence. These compounds can be divided into six easily identifiable classes based on plant material and extract. The table below lists each compound and how they affect vertebrates in general.

Answer 4

Some defence mechanisms in plant, are very intresting they close the petals once the insect is cought in it and fold and then digest it. After that it reopens the flower.

Answer 5

active and passivePresence of spines, thorns and unpleasent smell etc are the defence mechanisms in plants

Answer 6

The plant defense against insect pests includes an erection of a physical barrier either through the formation of a waxy cuticle or development of spines, setae, and trichomes.

Answer 7

Some plants are poisonous. Some have spines or thorns. Some have the ability to survive fires.