Plant Science

Modern plant science

A considerable amount of new knowledge today is being generated from studying model plants like Arabidopsis thaliana. This weedy species in the mustard family was one of the first plants to have its genome sequenced. The sequencing of the rice (Oryza sativa) genome, its relatively small genome, and a large international research community have made rice an important cereal/grass/monocot model. Another grass species, Brachypodium distachyon is also an experimental model for understanding genetic, cellular and molecular biology. Other commercially important staple foods like wheat, maize, barley, rye, pearl millet and soybean are also having their genomes sequenced. Some of these are challenging to sequence because they have more than two haploid (n) sets of chromosomes, a condition known as polyploidy, common in the plant kingdom. A green alga, Chlamydomonas reinhardtii, is model organism that has proven important in advancing knowledge of cell biology.

In 1998 the Angiosperm Phylogeny Group published a phylogeny of flowering plants based on an analysis of DNA sequences from most families of flowering plants. As a result of this work, major questions such as which families represent the earliest branches in the genealogy of angiosperms are now understood. Investigating how plant species are related to each other allows botanists to better understand the process of evolution in plants. Despite the study of model plants and DNA, there is continual on-going work and discussion among taxonomists about how best to classify plants into various taxa.

The Importance of plant science

Historically all living things were grouped as animals or plants, and botany covered all organisms not considered animals. Some organisms included in the field of botany are no longer considered to belong to the plant (plantae) kingdom, which obtain their energy via photosynthesis, these include bacteria (studied in bacteriology), fungi (mycology) including lichen-forming fungi (lichenology), non-chlorophyte algae (phycology) and viruses (virology). However, attention is still given to these groups by botanists, and fungi (including lichens), and photosynthetic protists are usually covered in introductory botany courses.

The study of plants is vital because they are a fundamental part of life on Earth, which generates the oxygen, food, fibres, fuel and medicine that allow humans and other life forms to exist. Through photosynthesis, plants absorb carbon dioxide, a greenhouse gas that in large amounts can affect global climate. Just as importantly for us, plants release oxygen into the atmosphere during photosynthesis. Additionally, they prevent soil erosion and are influential in the water cycle. Plants are crucial to the future of human society as they provide food, oxygen, beauty, medicine, habitat for animals, products for people, and create and preserve soil. Paleobotanists study ancient plants in the fossil record. It is believed that early in the Earth's history, the evolution of photosynthetic plants altered the global atmosphere of the earth, changing the ancient atmosphere by oxidation.

Virtually all foods come either directly from plants, or indirectly from animals that eat plants. Plants are the fundamental base of nearly all food chains because they use the energy from the sun and nutrients from the soil and atmosphere, converting them into a form that can be consumed and utilized by animals; this is what ecologists call the first trophic level. Botanists also study how plants produce food we can eat and how to increase yields and therefore their work is important in mankind's ability to feed the world and provide food security for future generations, for example, through plant breeding. Botanists also study weeds, plants which are considered to be a nuisance in a particular location. Weeds are a considerable problem in agriculture, and botany provides some of the basic science used to understand how to minimize 'weed' impact in agriculture and native ecosystems. Ethnobotany is the study of the relationships between plants and people, and when this kind of study is turned to the investigation of plant-people relationships in past times, it is referred to as archaeobotany or paleoethnobotany.

Fundamental life processes

Botanical research has long had relevance to the understanding of fundamental biological processes other than just botany. Fundamental life processes such as cell division and protein synthesis can be studied using plants without the moral issues that come with conducting studies upon animals or humans. Gregor Mendel discovered the genetic laws of inheritance in this fashion by studying Pisum sativum (pea) inherited traits such as shape. What Mendel learned from studying plants has had far reaching benefits outside of botany. Similarly, 'jumping genes' were discovered by Barbara McClintock while she was studying maize.

Medicine and materials

Many medicinal and recreational drugs, like tetrahydrocannabinol, caffeine, and nicotine come directly from the plant kingdom. Others are simple derivatives of botanical natural products; for example, aspirin is based on the pain killer salicylic acid which originally came from the bark of willow trees. As well, the narcotic analgesics such as morphine are derived from the opium poppy. There may be many novel cures for diseases provided by plants, waiting to be discovered. Popular stimulants like coffee, chocolate, tobacco, and tea also come from plants. Most alcoholic beverages come from fermenting plants such as barley (beer), rice (sake) and grapes (wine).

Hemp, cotton, wood, paper, linen, vegetable oils, some types of rope, and rubber are examples of materials made from plants. Silk can only be made by using the mulberry plant. Sugarcane, rapeseed, soy are some of the plants with a highly fermentable sugar or oil content which have recently been put to use as sources of biofuels, which are important alternatives to fossil fuels.

Climate Change: A global perspective

In many different ways, plants can act a little like the 'miners' canary', an early warning system alerting us to important changes in our environment. Plants respond to and provide understanding of changes in on the environment:

1. Plant systematics and taxonomy are essential to understanding habitat destruction and species extinction.

2. Ultraviolet radiation causes changes in plants which help in studying problems like ozone depletion.

3. Analysing pollen from by plants thousands or millions of years ago allows reconstruct of past climates and predicting future ones; which is essential to climate change research.

4. Study of plant life cycles is an important part of phenology, which is used in climate-change research.

The biology of a population is greater than the collective biologies of its individuals. Multiple members of the same species in close proximity constitute a population. Different populations in proximity constitute a community, which in conjunction with its non-living environment constitute an ecosystem. The relation of each organism to all other organisms and factors in its habitat and environment make up its ecology. This includes structure, genetics and mutations, metabolism, diversity, fitness, adaptation, climate, water, and soil condition.

The conditions that constitute an organism’s life cycle are its habitat. Both negative and beneficial interactions with other organisms are parts of a plant's ecology. Herbivores eat plants, but plants can also defend against them. Some other organisms form beneficial relationships with plants, called mutualisms, for example with mycorrhizal fungi that provide nutrients, and honey bees that pollinate flowers. A biome is a large part of the earth that has very similar abiotic and biotic factors, climate, and geography, creating a typical ecosystem over that area that is characterised by its dominant plants. Examples include tundra and tropical rainforest.

Evolutionary plant science

DNA provides the information for a plant's structure, metabolism, and biology. Genetics is the science of inheritance and the gene is its chemical basis. The same basic laws of genetics apply to both plants and animals. In sexual reproduction, offspring are often more fit than either parent since the stronger genes tend to be passed on to the next generation. Mutations and natural selection result in a species acquiring new traits and eventually evolving into one or more new species. Population genetics is the study of allele frequency distribution and change under the influence of the four main evolutionary processes: natural selection, genetic drift, mutation and gene flow. Changes can also be caused by natural events such as a large meteor hitting Earth and selective breeding (artificial selection) of plants by humans for specific traits.

Since the mid-20th century, there has been considerable debate over how the earliest forms of life evolved and how to classify them, especially at the kingdom and domain levels and organisms that are or have been considered bacteria. For example, the three-domain method separates Archaea and Bacteria, previously grouped into the single kingdom Monera (bacteria). In this system Eukaryota (nuclei-bearing eukaryotes). Archaea was separated because it was shown to have a completely separate evolutionary history. However, Thomas Cavalier-Smith rejects the three-domain system and places the Archea as a subkingdom of Bacteria. Cyanobacteria were once believed to be related to algae and hence studied by botanists. Even now they are studied by both botanists and bacteriologists. Similarly, the Fungi (or Myceteae) were once considered plants but there is now uncertainty about how to classify them.

The various divisions of algae are also taxonomically problematic as some are more clearly linked to plants than others. Their many differences in features such as biochemistry, pigmentation, and nutrient reserves show that they diverged very early in evolutionary time. The division Chlorophyta (green algae) is considered the ancestor of true plants.

Nonvascular plants are embryophytes that do not have vascular tissue: mosses, liverworts, and hornworts. Many plants that are called ‘moss’ actually are not. For example, Spanish moss (Tillandsia usneoides) is actually in the Bromeliaceae (pineapple) family. Nonvascular plants do not have xylem nor phloem. After the development of xylem and phloem, vascualar plants developed along two lines: Cryptogams (non-seed producing), which developed first, and spermatophytes (seed producing). Spermatophytes are plants that produce seeds. Gymnosperms produce unenclosed seeds. Gymnosperms are the ancestors of Angiosperms, which produce a seed encased in a structure such as a carpel.

Botanical physiology

Plant physiology is the energy the plant brings in acting upon materials brought into the plant via various mechanisms. Sunlight, either through photosynthesis or cellular respiration, is the basis of all life. Photoautotrophs gather energy directly from sunlight. This includes all green plants, cyanobacteria and other bacteria that can photosynthesize. Heterotrophs take in organic molecules and respire them. This includes all animals, all fungi, all completely parasitic plants, and non-photosynthetic bacteria. Respiration is the oxidation of carbon whereby it is broken down into simpler structures; essentially the opposite of photosynthesis.

Transport processes are those by which molecules are moved within the organism, such as: membranes transporting material across themselves and enzymes moving electrons. This is how minerals and water get from roots to other parts of the plant. Diffusion, osmosis, and active transport are different ways transport can occur. Examples of minerals that plants need are: nitrogen, phosphorous, phosphate, calcium, magnesium, and sulphur. Chemicals from the air, soil, and water in combination with sunlight form the basis of plant metabolism. Most of these elements come from minerals in a process called mineral nutrition. Few plants live in stable unchanging environments. Most plants most adapt to a variety of environmental factors, including changes in temperature, light and moisture. The better a plant can cope with these changing conditions, the more likely it can survive over both the short and long term as well as a wider geographic range. Cell types are unique and their nucleus stores most of the DNA.

Understanding the structure and function of cells is fundamental to all of the biological sciences. All organisms have cells. Cell biology studies their structural and physiological properties. This includes responses to stimuli, reproduction, and development on the macroscopic scale, microscopic scale, and molecular level. The similarities and differences between the function of a cell are quite varied. Plant cells are eukaryotic, have a membrane-encased nucleus that carries genetic material. With rare exceptions, plant cells also have a central vacuole, cytoplasm, cytosol, dictyosomes, endoplasmic reticulum, microbodies, microfilaments, microtubules, mitochondria, plasma membrane, plastids, protoplasm, ribosomes, storage products, and a cell wall. Cells divide by processes known as karyokinesis and cytokinesis.

The body of a plant contains three basic parts: roots, stems, and leaves. Roots anchor it to the ground, gather water and mineral nutrients from the soil, and produce hormones. Plants with horizontal-spreading roots, such as willows, produce shoots and those with fleshy taproots, such as beets and carrots, store carbohydrates. Stems provide support to the leaves and store nutrients. Leaves gather sunlight and begin photosynthesis. Large, flat, flexible, green leaves are called foliage leaves. Gymnosperms are seed-producing plants which have open seeds, such as conifers, cycads, Gingko, and gnetophyta. Angiosperms are seed-producing plants that produce flowers, having enclosed seeds. Some of the gymnosperms became the ancestors of the angiosperms. Woody plants, such as azaleas and oaks, undergo a secondary growth phase resulting in two additional types of tissues: wood (secondary xylem) and bark (secondary phloem and cork). All gymnosperms and many angiosperms are woody plants. Some plants reproduce sexually, some asexually, and some via both means.

Sub-disciplines of plant science

1. Agronomy— Application of plant science to crop production

2. Bryology— Mosses, liverworts, and hornworts

3. Cryptobotany— Study of plants largely considered nonexistent

4. Dendrology- Study of woody plants, shrubs, trees and lianas

5. Economic botany — Study of plants of economic use or value

6. Ethnobotany— Relationship between humans and plants

7. Forestry— Forest management and related studies

8. Horticulture— Cultivated plants

9. Lichenology— Lichens

10. Mycology — Fungi

11. Paleobotany — Fossil plants

12. Palynology — Pollen and spores

13. Phycology — Algae

14. Phytochemistry — Plant secondary chemistry and chemical processes

15. Phytopathology — Plant diseases

16. Plant anatomy — Cell and tissue structure

17. Plant ecology — Role of plants in the environment

18. Plant genetics — Genetic inheritance in plants

19. Plant morphology — Structure and life cycles

20. Plant neurobiology — Behavioral-like aspects

21. Plant physiology — Life functions of plants

22. Plant systematics — Classification and naming of plants

Famous plant scientists

1. Sculpture of Ibn al-Baitar among trees, Benalmádena, Málaga, Spain

2. The following botanists made major contributions to the ways in which botany has been studied.

3. Theophrastus (c. 371 – c. 287 BC), The Father of Botany, established botanical science through his lecture notes, Enquiry into Plants.

4. Pedanius Dioscorides (c. 40–90 AD), Greek physician, pharmacologist, toxicologist and botanist, author of De Materia Medica (Regarding Medical Matters).

5. Abū Ḥanīfa Dīnawarī (828–896), Persian botanist, historian, geographer, astronomer, mathematician, and founder of Arabic botany.

6. Su Song (1020–1101), Chinese polymath, botanist, compiled the Bencao Tujing ('Illustrated Pharmacopoeia', a treatise on pharmaceutical botany, zoology, and mineralogy.

7. Abu al-Abbas al-Nabati (c. 1200), Andalusian-Arab botanist and agricultural scientist, and a pioneer in experimental botany.

8. Ibn al-Baitar (1197–1248), Andalusian-Arab scientist, botanist, pharmacist, physician, and author of one of the largest botanical encyclopedias.

9. Leonardo da Vinci (1452–1519), Italian polymath; a scientist, mathematician, engineer, inventor, anatomist, painter, sculptor, architect, botanist, musician and writer.

10. John Ray (1627–1705), English naturalist, botanist, and zoologist; father of natural history.

11. Augustus Quirinus Rivinus, German physician and botanist; introduced the concept of classifying plants based on the structure of their flower, which influenced de Tournefort and Linnaeus.

12. Joseph Pitton de Tournefort (1656–1708), French botanist; first to clearly define the concept of genus for plants.

13. Carl Linnaeus (1707–1778), Swedish botanist, physician and zoologist who laid the foundations for the modern scheme of Binomial nomenclature; known as the father of modern taxonomy and also considered one of the fathers of modern ecology.

14. Jean-Baptiste Lamarck, (1744–1829), French naturalist, botanist, biologist, academic, and an early proponent of the idea that evolution occurred and proceeded in accordance with natural laws.

15. Aimé Bonpland (1773–1858), French explorer and botanist, who accompanied Alexander von Humboldt during five years of travel in Latin America.

16. Augustin Pyramus de Candolle (1778–1841), Swiss botanist, originated the idea of "Nature's war", which influenced Charles Darwin.

17. David Douglas (1799–1834), Scottish botanical explorer of North America and China, who imported many ornamental plants into Europe.

18. Richard Spruce (1817–1893), English botanist and explorer who carried out a detailed study of the Amazon flora.

19. Joseph Dalton Hooker (1817–1911), English botanist and explorer; second winner of Darwin Medal.

20. Gregor Johann Mendel (1822–1884), Austrian Augustinian priest and scientist, and is often called the father of genetics for his study of the inheritance of traits in pea plants.

21. Thomas Henry Huxley (1825–1895), English biologist, known as "Darwin's Bulldog" for his advocacy of Charles Darwin's theory of evolution; third winner of Darwin Medal.

22. Charles Sprague Sargent (1841–1927), American botanist, the first director of the Arnold Arboretum at Harvard University.

23. Agustín Stahl (1842–1917), Puerto Rican doctor, who conducted investigations and experiments in the fields of botany, ethnology, and zoology in the Caribbean region.

24. Luther Burbank (1849–1926), American botanist, horticulturist, and a pioneer in agricultural science.

25. George Ledyard Stebbins, Jr. (1906–2000), American widely regarded as one of the leading evolutionary biologists of the 20th century, developed a comprehensive synthesis of plant evolution incorporating genetics.

26. Carlos Muñoz Pizarro (1913–1976), Chilean botanist, known for his studies of the Chilean flora and its conservation.

27. Norman Borlaug (1914-2009), American agronomist, known for breeding high yielding wheat varieties. Dubbed the father of the green revolution

28. Richard Evans Schultes (1915–2001), American botanist and explorer, known as The Father of Ethnobotany, Linnean Society gold medal winner