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I observed on most collected stones the imprints of innumerable plant fragments which were so different from those which are growing in the Lyonnais, in the nearby provinces, and even in the rest of France, that I felt like collecting plants in a new world... The number of these leaves, the way they separated easily, and the great variety of plants whose imprints I saw, appeared to me just as many volumes of botany representing in the same quarry the oldest library of the world.
Antoine de Jussieu, French physician and botanist, 1718

The kingdom Plantae constitutes a large and varied group of organisms, which have been on the planet for a very long time. There are more than 300,000 species of catalogued plants, including the fossil plants that de Jussieu references in the epigraph above. Of these, more than 260,000 are seed plants. Mosses, ferns, conifers, and flowering plants are all members of the plant kingdom. While there is some disagreement about the relationships between Chlorophytes, Charophytes, and Plantae, there are several unique characteristics which these groups share. Only green algae and plants use chlorophyll a and b plus carotene in a particular ratio. They share the trait of cellulose-rich cell walls, and there is strong molecular support for their close relationship.

The ancestors of the green algae became photosynthetic by engulfing a green, photosynthetic bacterium about 1.65 billion years ago. This captured bacterium evolved into a chloroplast. That algal line evolved into the Charophytes, bryophytes, seedless vascular plants, gymnosperms, and angiosperms.

Several other groups of eukaryotes have common names that include ‘algae.’ In the latest classification red algae are included in Archaeplastida, while brown algae and golden algae are in a separate supergroup. In contrast to the green algae, red, golden, and brown algae all became photosynthetic by secondary, or even tertiary, endosymbiotic events. In other words, the cells that evolved into red, brown, or golden algae all engulfed cells that had already engulfed a photosynthetic bacterium. These algae are also photosynthetic autotrophs, but they did not diversify to the same extent as the Charophytes, nor did they colonize land.

Plant adaptations to life on land

In order for plants to invade land, they had to contend with several challenges in the terrestrial environment. Water has been described as “the stuff of life.” The cell’s interior is a watery soup: in this medium, most small molecules can dissolve and diffuse rapidly, and the majority of the chemical reactions of metabolism take place. The first challenge, Desiccation , or drying out, is a constant danger for an organism exposed to air. Even when parts of a plant are close to a source of water, the aerial structures are likely to dry out. Second, Water also provides buoyancy to organisms. On land, plants need to develop structural support in a medium that does not give the same support as water. The organism is also subject to bombardment by mutagenic radiation, because air does not filter out ultraviolet rays of sunlight like water does. Additionally, the male gametes must reach the female gametes using new strategies, because swimming is no longer possible. Lastly, both gametes and zygotes must be protected from desiccation. The successful land plants developed strategies to deal with all of these challenges. Not all adaptations appeared at once. Some species never moved very far from the aquatic environment, whereas others went on to conquer the driest environments on Earth.

Questions & Answers

Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Principles of biology. OpenStax CNX. Aug 09, 2016 Download for free at http://legacy.cnx.org/content/col11569/1.25
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