Select your language

Suggested languages for you:
Log In Start studying!
StudySmarter - The all-in-one study app.
4.8 • +11k Ratings
More than 3 Million Downloads
Free
|
|

All-in-one learning app

  • Flashcards
  • NotesNotes
  • ExplanationsExplanations
  • Study Planner
  • Textbook solutions
Start studying

Plant Biology

Save Save
Print Print
Edit Edit
Sign up to use all features for free. Sign up now

Want to get better grades?

Nope, I’m not ready yet

Get free, full access to:

  • Flashcards
  • Notes
  • Explanations
  • Study Planner
  • Textbook solutions
Plant Biology

Plants: we eat them, use them for decoration, and even consider some of them signs of good luck. Without them, the air we breathe would be inhospitable to us, as they put much-needed oxygen into the atmosphere. Surely, plants provide us with many uses, so why wouldn't there be a whole branch of biology dedicated to them?

Plant biology is the branch of biology that deals with studying plants. In particular, plant biologists look at the evolution, life history, structure, and function of plants.

Introduction to plant biology

Plant biologists have many roles. Some study the chemical signals plants use to defend themselves, others may study the way the climate affects a plant's ability to reproduce.

Plant biology is a large branch of science that focuses on plants including, but not limited to, their evolution, life history, structure, and function.

Plant biology is a wide-reaching subject, but some categories receive more attention based on their importance to us and our interests. See below for more about the different categories of plant biology:

  1. Evolution: We study the adaptations that plants have acquired which have helped them to diversify and occupy new environments.

  2. Life history: We study the length of a plant's life and the style of reproduction.

  3. Plant structure: From the chloroplast to the whole plant, plant structure can tell us about what makes a plant unique and how it survives in its environment.

  4. Function: We study plant function to understand how plants work.

The definition of a plant in biology

Plants are multicellular, eukaryotic organisms that have chloroplasts for photosynthesis.

Scientists believe that the beginning of plants occurred when a eukaryote engulfed a cyanobacterium. Cyanobacteria are bacteria that can photosynthesize, and so it is believed this led to the development of the chloroplast in plants. This theory is called primary endosymbiosis.

Many plants that we traditionally think of as a "plant" would most likely fall under the category of "green plants", which have the pigment chlorophyll b (as well as chlorophyll a, which the rest of the plants have). Other types of organisms that are technically plants include red algae!

For the purpose of AP biology, we will be concerned with the land plants, which are a major group within the "green plants" that developed a number of adaptations to survive on land. These plants are typically split into nonvascular plants (mosses, hornworts, and liverworts) and vascular plants (trees, ferns, horsetails, and many more).

Plant cell: diagram and its biology

The plant cell, because it is eukaryotic, contains a membrane-bound nucleus and a number of organelles. Below, important parts of the plant cell are highlighted. You may notice that many of the organelles are also shared with animal cells (Fig. 1).

Plant Biology Plant cell diagram Source: LadyofHats, Wikipedia | StudySmarterFigure 1: Diagram of a plant cell. Source: Self-made by LadyofHats, via Wikipedia.

Plant specific organelles

  • Chloroplast: Chloroplasts are the site of photosynthesis. They help plant cells capture the sun's energy to use to make sugars. The plant can then use those sugars as food.
  • Vacuole: Vacuoles are storage sites in cells for water, nutrients, and some byproduct chemicals from cell processes. In a plant cell, the big vacuoles at the center of the cell are filled with water and help provide stability to the plant cells.
  • Cell wall: Unlike animal cells, plant cells have a cell wall, fortified by cellulose, which provides support for the structure of the plant. Plants do not have skeletons like some animals do, so having cell walls provides some rigidity for plants.
  • Plasmodesmata: The plasmodesmata are small junctions in plant cell walls that connect the cytoplasm of adjacent cells.

Organelles shared with animal cells

  • Peroxisomes: These organelles help to break down chemicals that are toxic, known as peroxides. They are more common in plants, but also are found in animal cells.
  • Ribosomes: Ribosomes are points of protein synthesis, cells have both free ribosomes in the cytoplasm, and ribosomes attached to the rough endoplasmic reticulum.
  • Rough and smooth endoplasmic reticulum (ER): The rough ER has ribosomes where proteins are made. The smooth ER has a number of functions, including making products that the cell needs (i.e. lipids).
  • Golgi apparatus: Ribosomes help to make proteins for the cell, while the Golgi apparatus packages and processes these proteins for use inside or outside of the cell.
  • Mitochondria: Mitochondria help to produce energy from the sugars that the plant makes in its chloroplasts.
  • Nucleus and nucleolus: The nucleus is the site for DNA storage as chromatin. In the nucleus, the nucleolus is the site where ribosomes begin construction, before being finished in the cytoplasm.

Plant biology: life cycles and reproduction

One quality of all land plants (nonvascular and vascular plants) is the life cycle mechanism, known as the alternation of generations. In the alternation of generations life cycle, a plant goes through both a multicellular diploid stage and a multicellular haploid stage.

Below, the basic steps of alternation of generations are highlighted, starting with the diploid plant:

  1. The diploid multicellular plant, called a sporophyte, will produce spores via meiosis.

  2. The spores will grow into a haploid plant, called a gametophyte.

  3. The gametophyte will produce gametes via mitosis (NOT meiosis).

  4. Two gametes when brought together, or fertilized, form a diploid zygote which will begin the process again.

Plants can reproduce both sexually and asexually, if you need a refresher on these types of reproduction visit the article on Heredity.

Plant Biology diagram of alternation of generations Source: Peter Coxhead (Wikimedia) | StudySmarterFigure 2: Alternation of generations diagram. Source: Peter Coxhead, via Wikimedia Commons.

Notice in the diagram above (Fig. 2) that plants produce haploid spores via meiosis, but gametes (sex cells) are produced via mitosis. Because plants have a haploid gametophyte generation, gametes must be produced by mitosis, unlike in other organisms (like humans), who produce gametes by meiosis.

Plant biology: structure, function, and adaptations

Land plants are of particular interest to us and biologists because they had to evolve to be able to survive on land, meaning they have many adaptations to new problems faced on land, like desiccation (drying out), retaining structure, and getting water and nutrients from the soil.

Evolution of land plants: adaptations and their importance

Land plants can be split into two major groups: nonvascular plants and vascular plants. The main adaptation connecting all land plants is that their embryos have protection from drying out from maternal tissue. This adaptation allowed plants the ability to reproduce on land and was, therefore, an important first step for terrestrial plant species (Fig. 3).

Plant Biology Cladogram of land plant evolution Source: Sigel et al. 2018, Frontiers in Plant Science | StudySmarterFigure 3: Diagram of land plant evolution, from bryophytes to angiosperms, with important adaptations highlighted. Source: Sigel et al. 2018, Frontiers in Plant Science.

Nonvascular plants do not have vascular systems and therefore grow only a few inches tall. Vascular plants all have vascular systems, which function to transport water and nutrients throughout the plants.

What are some ways that we protect ourselves from losing too much water? It's the largest organ in our body and, although we may apply moisturizer, it has its own defenses against drying out. You guessed it, it's skin! Land plants also sometimes have their own version of the skin, called a cuticle. Cuticles are waxy coverings that help to keep water from escaping a plant.

Plant structure and function

The structure and function of plants are two closely related categories of plant biology. Biologists who study plant structure and function may say they study "plant physiology", a formal term for these branches of plant biology. The structure of plants is often split into the root system and the shoot system. The root system includes the roots and the shoot system includes the stem and the leaves.

Roots

Roots have evolved to help to anchor a plant and absorb water and nutrients. They vary greatly from plant to plant, but they can grow extensive lengths to help keep plants anchored in the soil. Roots also have special extensions of their cells called root hairs. Root hairs help increase the surface area of the root so that more water and nutrients can be absorbed more efficiently.

Roots also have vascular tissue in them (the xylem and phloem) which allows them to transport water and mineral directly from the soil to the plant. Additionally, the root tip is a place of mitosis- meaning the root system of plants can grow as plants get larger.

Stems

The stems of the plant are the long, central plant body. For example, the trunk of the tree is the centralized plant body.

Stems are composed of vascular tissue (xylem and phloem) and other types of tissues, some of which are strengthened by proteins that provide support for the plant against outside forces (wind, rain, etc.).

Leaves

Leaves have vascular tissue (veins) and photosynthetic tissue (mesophyll). The mesophyll tissue of leaves contain chloroplasts, which makes it the site of photosynthesis, or sugar production. Additionally, leaves are often thin and broad, allowing for a large surface area in which a plant can capture light energy from the sun (in the form of photons).

Leaves also have stomata, which are typically located on their undersides. Stomata are cell openings that are controlled by guard cells. Guard cells function by opening to let CO2 into the plant for photosynthesis and closing back up to protect from too much water getting out.

Plant Biology - Key takeaways

  • Plant biology is a branch of biology dealing specifically with plants including their evolution, life history, structure, and function. As a result, plant biologists study a specific part of one of these parts of plant biology or a combination of two or more.
  • Plants are multicellular, eukaryotic organisms that can produce their own food via chloroplasts or organelles where photosynthesis takes place.
  • Plants have both diploid (sporophyte) and haploid (gametophyte) generations, the dominant generation in nonvascular plants is the haploid gametophyte, and the dominant generation in vascular plants is the diploid sporophyte.
  • Plants produce gametes via mitosis NOT meiosis.
  • Vascular plants have roots, stems, and leaves that help carry out specific functions such as anchoring the plants and absorbing nutrients, transporting nutrients, and carrying out photosynthesis respectively.

Frequently Asked Questions about Plant Biology

Plants are important model organisms for science. Scientists may study plant genes to understand more about genetics, evolution, or biochemical processes. 


Additionally, plants are important parts of their ecosystems, so understanding their relationships with other organisms is important to keeping ecosystems resilient in the face of climate change. 


Plants are also the number one source of food crops for most of the world including rice, corn, wheat, and soybeans. Scientists can genetically modify plants to make them more resilient against pests or other dangers to crops. 

Plant breeding is the science of selecting for specific traits in plants by the creation of new subvarieties of plants. This may be done to increase resilience to pests in agriculture or to produce a desired aesthetic in horticulture. 

Plants grow like other organisms through cell growth and mitosis. Plants also have a tissue that can turn into any type of tissue because it is undifferentiated. This is called meristematic tissue. This tissue allows for plants to continuously grow if the proper resources are available to the plant. Think large, old-growth forests where towering trees are hundreds of years old!

Plant biology is the branch of biology that deals with studying plants. In particular, plant biologists like to look at the evolution, life history, structure, and function of plants.

Plant biologists study a wide variety of topics related to plants. In particular, they may look at plant structure and function, the evolution of plants, or the life cycle and reproductive patterns of plants.

Final Plant Biology Quiz

Question

What is a sink?

Show answer

Answer

A portion of the plant that keeps growing

Show question

Question

What is a source?

Show answer

Answer

A source is a part of the plant that creates organic compounds

Show question

Question

Translocation is bi-directional

Show answer

Answer

True

Show question

Question

How many specialized cells are there in the phloem?

Show answer

Answer

4

Show question

Question

Which are examples of sources?

Show answer

Answer

Green leaves

Show question

Question

Which are examples of sinks?

Show answer

Answer

Roots

Show question

Question

Phloem is living tissue

Show answer

Answer

True

Show question

Question

Which is correct?

Show answer

Answer

The symplastic pathway is via cell cytoplasms and the apoplastic pathway is via cell walls

Show question

Question

What are the four specialized cell types? 

Show answer

Answer

Sieve tube elements, companion cells, phloem fibers, and parenchyma cells

Show question

Question

How do companion cells help sieve tubes?

Show answer

Answer

They provide metabolic support

Show question

Question

What do sieve tubes do? 

Show answer

Answer

They transport amino acids and sugars

Show question

Question

What do phloem fibers do?

Show answer

Answer

Provide structural support for the plant

Show question

Question

What are parenchyma cells?

Show answer

Answer

They are permanent ground tissue 

Show question

Question

ATP is needed to transport assimilates between the sources and sinks

Show answer

Answer

True

Show question

Question

What is plasmodesmata? 

Show answer

Answer

They are intracellular channels along the plant cell wall and facilitate the exchange of sucrose and signaling molecules between cells

Show question

Question

What are the functions of xylem?

Show answer

Answer

It transports water and inorganic ions while also providing support for the plant

Show question

Question

Xylem forms a vascular bundle with phloem 

Show answer

Answer

True

Show question

Question

What is a source?

Show answer

Answer

It is where the plant creates the food like the leaves

Show question

Question

What is a sink?

Show answer

Answer

It is where the food is stored or used like the roots

Show question

Question

Transpiration is unidirectional

Show answer

Answer

True

Show question

Question

How many specialized cells are there in xylem?

Show answer

Answer

4

Show question

Question

What are tracheids? 

Show answer

Answer

Long and narrow hardened cells with pits

Show question

Question

Xylem is completely a living tissue

Show answer

Answer

False

Show question

Question

What is the function of parenchyma? 

Show answer

Answer

It is the only living tissue in xylem and it stores oils and starches

Show question

Question

What are sclerenchyma? 

Show answer

Answer

They are xylem fibers

Show question

Question

What are the two xylem vessel elements?

Show answer

Answer

Meta-xylem and proto-xylem 

Show question

Question

What provides mechanical strength for the xylem in the plant?

Show answer

Answer

Lignin

Show question

Question

How are xylem and phloem organized in dicots? 

Show answer

Answer

Ring-like structures

Show question

Question

How are xylem and phloem organized in monocots? 

Show answer

Answer

Scattered

Show question

Question

What are the five differences between monocots and dicots? 

Show answer

Answer

The seeds, the roots, the vascular structure of the stem, the leaves, and the flowers

Show question

Question

If life evolved in water, how did land plants migrate to the terrestrial world?

Show answer

Answer

Lands plants migrated to land once. All land plants share a single common ancestor known as ancestral streptophyte algae


The similarity in the stress signaling pathways between modern plants and ancestral streptophyte algae has been shown to be very high suggesting these pathways were beneficial for adapting to lands many stressors. 

Show question

Question

When did early ancestral plants make the move to land?

Show answer

Answer

Ancestral streptophyte algae moved to land roughly 430 million years ago. 

Show question

Question

Once on land why was it important for plants to adapt to their environment?

Show answer

Answer

Modern plants and ancestral streptophyte algae share complex signalling pathways. This suggests it was harsh transition from aquatic to terrestrial environments. In the novel terrestrial environment it was crucial plants evolved desiccation strategies to survive the dry conditions. 


Further evolution was critical to reduce competition for resources, resist against UV damage, and disperse into new environments. 

Show question

Question

Which feature of ancestral streptophyte algae may have been beneficial for surviving early terrestrial environments?

Show answer

Answer

Cell walls containing lignin like compounds

Show question

Question

Which of the following could NOT be considered a beneficial adaptation to avoid dessication?

Show answer

Answer

Protective Flavonoids and Pigments

Show question

Question

In what period did early angiosperms evolve?

Show answer

Answer

Cretaceous period

Show question

Question

True or False: Angiosperms (flowering plants) and pollinators are thought to have coevolved?

Show answer

Answer

True

Show question

Question

When did early vascular plants emerge? 

Show answer

Answer

Late Devonian Period

Show question

Question

What group of plants are the most abundant in modern times? 

Show answer

Answer

Angiosperms / Flowering Plants

Show question

Question

What is the name for the evolutionary mechanisms which favours traits that confer increased survivability to the individual? 

Show answer

Answer

Natural Selection

Show question

Question

Which theory best describes the origins of all life on earth?

Show answer

Answer

Universal Common Ancestor 

Show question

Question

How long ago did the first life form evolve?

Show answer

Answer

6 Billion years ago

Show question

Question

Which of the following is NOT a characteristic of a vascular plant?

Show answer

Answer

Dominant gametophyte (haploid) generation

Show question

Question

What are the veins that transport water and nutrients throughout plants, formed from the xylem and phloem tissues?

Show answer

Answer

Vascular bundles

Show question

Question

True or false: Xylem cells are not alive and fortified with the protein lignin. 

Show answer

Answer

True

Show question

Question

True or false: Phloem cells are alive and are not fortified by the protein lignin.

Show answer

Answer

True

Show question

Question

The evaporation of water through the leaves of vascular plants is known as...

Show answer

Answer

transpiration.

Show question

Question

Which of the following is NOT a vascular plant?

Show answer

Answer

Mosses

Show question

Question

Which of the following is NOT a non-vascular plant?

Show answer

Answer

Clubmosses

Show question

Question

Which of the following is a property of the non-vascular plants?

Show answer

Answer

Does not have a vascular system

Show question

60%

of the users don't pass the Plant Biology quiz! Will you pass the quiz?

Start Quiz

Discover the right content for your subjects

No need to cheat if you have everything you need to succeed! Packed into one app!

Study Plan

Be perfectly prepared on time with an individual plan.

Quizzes

Test your knowledge with gamified quizzes.

Flashcards

Create and find flashcards in record time.

Notes

Create beautiful notes faster than ever before.

Study Sets

Have all your study materials in one place.

Documents

Upload unlimited documents and save them online.

Study Analytics

Identify your study strength and weaknesses.

Weekly Goals

Set individual study goals and earn points reaching them.

Smart Reminders

Stop procrastinating with our study reminders.

Rewards

Earn points, unlock badges and level up while studying.

Magic Marker

Create flashcards in notes completely automatically.

Smart Formatting

Create the most beautiful study materials using our templates.

Sign up to highlight and take notes. It’s 100% free.