Exposing Plants To an Unusual Chemical Early on May Bolster Their Growth and Help Feed The World
AP Photo/Gerry Broome
Just like any other organism, plants can get stressed. Usually it’s conditions like heat and drought that lead to this stress, and when they’re stressed, plants might not grow as large or produce as much. This can be a problem for farmers, so many scientists have tried genetically modifying plants to be more resilient.
But plants modified for higher crop yields tend to have a lower stress tolerance because they put more energy into growth than into protection against stresses. Similarly, improving the ability of plants to survive stress often results in plants that produce less because they put more energy into protection than into growth. This conundrum makes it difficult to improve crop production.
I have been studying how the plant hormone ethylene regulates growth and stress responses in plants. In a study published in July 2023, my lab made an unexpected and exciting observation. We found that when seeds are germinating in darkness, as they usually are underground, adding ethylene can increase both their growth and stress tolerance….Continue reading…
Source: Exposing plants to an unusual chemical early on may bolster their growth and help feed the world
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The ancestors of land plants evolved in water. An algal scum formed on the land 1,200 million years ago, but it was not until the Ordovician, around 450 million years ago, that the first land plants appeared, with a level of organisation like that of bryophytes.However, evidence from carbon isotope ratios in Precambrian rocks suggests that complex plants developed over 1000 mya.
Primitive land plants began to diversify in the late Silurian, around 420 million years ago. Bryophytes, club mosses, and ferns then appear in the fossil record. Early plant anatomy is preserved in cellular detail in an early Devonian fossil assemblage from the Rhynie chert. These early plants were preserved by being petrified in chert formed in silica-rich volcanic hot springs.
By the end of the Devonian, most of the basic features of plants today were present, including roots, leaves and secondary wood in trees such as Archaeopteris. The Carboniferous Period saw the development of forests in swampy environments dominated by clubmosses and horsetails, including some as large as trees, and the appearance of early gymnosperms, the first seed plants.
The Permo-Triassic extinction event radically changed the structures of communities. This may have set the scene for the evolution of flowering plants in the Triassic (~200 million years ago), with an adaptive radiation in the Cretaceous so rapid that Darwin called it an “abominable mystery“. Conifers diversified from the Late Triassic onwards, and became a dominant part of floras in the Jurassic.
Plant cells have distinctive features that other eukaryotic cells (such as those of animals) lack. These include the large water-filled central vacuole, chloroplasts, and the strong flexible cell wall, which is outside the cell membrane. Chloroplasts are derived from what was once a symbiosis of a non-photosynthetic cell and photosynthetic cyanobacteria. The cell wall, made mostly of cellulose, allows plant cells to swell up with water without bursting. The vacuole allows the cell to change in size while the amount of cytoplasm stays the same.
Most plants are multicellular. Plant cells differentiate into multiple cell types, forming tissues such as the vascular tissue with specialized xylem and phloem of leaf veins and stems, and organs with different physiological functions such as roots to absorb water and minerals, stems for support and to transport water and synthesized molecules, leaves for photosynthesis, and flowers for reproduction.
When reproducing sexually, plants have complex lifecycles involving alternation of generations. One generation, the sporophyte, which is diploid (with 2 sets of chromosomes), gives rise to the next generation, the gametophyte, which is haploid (with one set of chromosomes). Some plants also reproduce asexually via spores. In some non-flowering plants such as mosses, the sexual gametophyte forms most of the visible plant.
In seed plants (gymnosperms and flowering plants), the sporophyte forms most of the visible plant, and the gametophyte is very small. Flowering plants reproduce sexually using flowers, which contain male and female parts: these may be within the same (hermaphrodite) flower, on different flowers on the same plant, or on different plants. The pollen produces male gametes that enter the ovule to fertilize the egg cell of the female gametophyte.
Fertilization takes place within the carpels or ovaries, which develop into fruits that contain seeds. Fruits may be dispersed whole, or they may split open and the seeds dispersed individually. Plants reproduce asexually by growing any of a wide variety of structures capable of growing into new plants. At the simplest, plants such as mosses or liverworts may be broken into pieces, each of which may regrow into whole plants. The propagation of flowering plants by cuttings is a similar process.
Structures such as runners enable plants to grow to cover an area, forming a clone. Many plants grow food storage structures such as tubers or bulbs which may each develop into a new plant. Some non-flowering plants, such as many liverworts, mosses and some clubmosses, along with a few flowering plants, grow small clumps of cells called gemmae which can detach and grow.
Plants have some of the largest genomes among all organisms. The largest plant genome (in terms of gene number) is that of wheat (Triticum aestivum), predicted to encode ≈94,000 genes and thus almost 5 times as many as the human genome. The first plant genome sequenced was that of Arabidopsis thaliana which encodes about 25,500 genes. In terms of sheer DNA sequence, the smallest published genome is that of the carnivorous bladderwort (Utricularia gibba) at 82 Mb (although it still encodes 28,500 genes) while the largest, from the Norway spruce (Picea abies), extends over 19.6 Gb (encoding about 28,300 genes).
Plants are distributed almost worldwide. While they inhabit several biomes which can be divided into a multitude of ecoregions, only the hardy plants of the Antarctic flora, consisting of algae, mosses, liverworts, lichens, and just two flowering plants, have adapted to the prevailing conditions on that southern continent. Plants are often the dominant physical and structural component of the habitats where they occur.
Many of the Earth’s biomes are named for the type of vegetation because plants are the dominant organisms in those biomes, such as grassland, savanna, and tropical rainforest. The photosynthesis conducted by land plants and algae is the ultimate source of energy and organic material in nearly all ecosystems. Photosynthesis, at first by cyanobacteria and later by photosynthetic eukaryotes, radically changed the composition of the early Earth’s anoxic atmosphere, which as a result is now 21% oxygen.
Animals and most other organisms are aerobic, relying on oxygen; those that do not are confined to relatively rare anaerobic environments. Plants are the primary producers in most terrestrial ecosystems and form the basis of the food web in those ecosystems.
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