Meristem: A group of plant cells that are capable of dividing infinitely and whose main function is the production of new growth at the growing tip of a root or stem. (From Concise Dictionary of Biology, 1990)Plant Shoots: New immature growth of a plant including stem, leaves, tips of branches, and SEEDLINGS.Gene Expression Regulation, Plant: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action in plants.Arabidopsis: A plant genus of the family BRASSICACEAE that contains ARABIDOPSIS PROTEINS and MADS DOMAIN PROTEINS. The species A. thaliana is used for experiments in classical plant genetics as well as molecular genetic studies in plant physiology, biochemistry, and development.Arabidopsis Proteins: Proteins that originate from plants species belonging to the genus ARABIDOPSIS. The most intensely studied species of Arabidopsis, Arabidopsis thaliana, is commonly used in laboratory experiments.Flowers: The reproductive organs of plants.Genes, Plant: The functional hereditary units of PLANTS.Plant Proteins: Proteins found in plants (flowers, herbs, shrubs, trees, etc.). The concept does not include proteins found in vegetables for which VEGETABLE PROTEINS is available.Inflorescence: A cluster of FLOWERS (as opposed to a solitary flower) arranged on a main stem of a plant.Cytokinins: Plant hormones that promote the separation of daughter cells after mitotic division of a parent cell. Frequently they are purine derivatives.Plant Roots: The usually underground portions of a plant that serve as support, store food, and through which water and mineral nutrients enter the plant. (From American Heritage Dictionary, 1982; Concise Dictionary of Biology, 1990)Indoleacetic Acids: Acetic acid derivatives of the heterocyclic compound indole. (Merck Index, 11th ed)MADS Domain Proteins: A superfamily of proteins that share a highly conserved MADS domain sequence motif. The term MADS refers to the first four members which were MCM1 PROTEIN; AGAMOUS 1 PROTEIN; DEFICIENS PROTEIN; and SERUM RESPONSE FACTOR. Many MADS domain proteins have been found in species from all eukaryotic kingdoms. They play an important role in development, especially in plants where they have an important role in flower development.Plants, Genetically Modified: PLANTS, or their progeny, whose GENOME has been altered by GENETIC ENGINEERING.Plant Leaves: Expanded structures, usually green, of vascular plants, characteristically consisting of a bladelike expansion attached to a stem, and functioning as the principal organ of photosynthesis and transpiration. (American Heritage Dictionary, 2d ed)Plant Stems: Parts of plants that usually grow vertically upwards towards the light and support the leaves, buds, and reproductive structures. (From Concise Dictionary of Biology, 1990)Homeodomain Proteins: Proteins encoded by homeobox genes (GENES, HOMEOBOX) that exhibit structural similarity to certain prokaryotic and eukaryotic DNA-binding proteins. Homeodomain proteins are involved in the control of gene expression during morphogenesis and development (GENE EXPRESSION REGULATION, DEVELOPMENTAL).Zea mays: A plant species of the family POACEAE. It is a tall grass grown for its EDIBLE GRAIN, corn, used as food and animal FODDER.Microscopy, Electron, Scanning: Microscopy in which the object is examined directly by an electron beam scanning the specimen point-by-point. The image is constructed by detecting the products of specimen interactions that are projected above the plane of the sample, such as backscattered electrons. Although SCANNING TRANSMISSION ELECTRON MICROSCOPY also scans the specimen point by point with the electron beam, the image is constructed by detecting the electrons, or their interaction products that are transmitted through the sample plane, so that is a form of TRANSMISSION ELECTRON MICROSCOPY.RNA, Plant: Ribonucleic acid in plants having regulatory and catalytic roles as well as involvement in protein synthesis.Plant Growth Regulators: Any of the hormones produced naturally in plants and active in controlling growth and other functions. There are three primary classes: auxins, cytokinins, and gibberellins.Plant Root Cap: A cone-shaped structure in plants made up of a mass of meristematic cells that covers and protects the tip of a growing root. It is the putative site of gravity sensing in plant roots.Phenotype: The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Oryza sativa: Annual cereal grass of the family POACEAE and its edible starchy grain, rice, which is the staple food of roughly one-half of the world's population.Seedling: Very young plant after GERMINATION of SEEDS.Plant Vascular Bundle: A strand of primary conductive plant tissue consisting essentially of XYLEM, PHLOEM, and CAMBIUM.DNA, Plant: Deoxyribonucleic acid that makes up the genetic material of plants.Gene Expression Regulation, Developmental: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action during the developmental stages of an organism.Plant Development: Processes orchestrated or driven by a plethora of genes, plant hormones, and inherent biological timing mechanisms facilitated by secondary molecules, which result in the systematic transformation of plants and plant parts, from one stage of maturity to another.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Cotyledon: A part of the embryo in a seed plant. The number of cotyledons is an important feature in classifying plants. In seeds without an endosperm, they store food which is used in germination. In some plants, they emerge above the soil surface and become the first photosynthetic leaves. (From Concise Dictionary of Biology, 1990)Angiosperms: Members of the group of vascular plants which bear flowers. They are differentiated from GYMNOSPERMS by their production of seeds within a closed chamber (OVARY, PLANT). The Angiosperms division is composed of two classes, the monocotyledons (Liliopsida) and dicotyledons (Magnoliopsida). Angiosperms represent approximately 80% of all known living plants.Seeds: The encapsulated embryos of flowering plants. They are used as is or for animal feed because of the high content of concentrated nutrients like starches, proteins, and fats. Rapeseed, cottonseed, and sunflower seed are also produced for the oils (fats) they yield.In Situ Hybridization: A technique that localizes specific nucleic acid sequences within intact chromosomes, eukaryotic cells, or bacterial cells through the use of specific nucleic acid-labeled probes.Flowering Tops: Tops of plants when in flower, including the stems, leaves and blooms.Gibberellins: A class of plant growth hormone isolated from cultures of Gibberella fujikuroi, a fungus causing Bakanae disease in rice. There are many different members of the family as well as mixtures of multiple members; all are diterpenoid acids based on the gibberellane skeleton.Plant Epidermis: A thin layer of cells forming the outer integument of seed plants and ferns. (Random House Unabridged Dictionary, 2d ed)Zeatin: An aminopurine factor in plant extracts that induces cell division. (Grant & Hackh's Chemical Dict, 5th ed)Plant Cells: Basic functional unit of plants.Coniferophyta: A plant division of GYMNOSPERMS consisting of cone-bearing trees and shrubs.Phloem: Plant tissue that carries nutrients, especially sucrose, by turgor pressure. Movement is bidirectional, in contrast to XYLEM where it is only upward. Phloem originates and grows outwards from meristematic cells (MERISTEM) in the vascular cambium. P-proteins, a type of LECTINS, are characteristically found in phloem.Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Plant Tubers: An enlarged underground root or stem of some plants. It is usually rich in carbohydrates. Some, such as POTATOES, are important human FOOD. They may reproduce vegetatively from buds.Genes, Homeobox: Genes that encode highly conserved TRANSCRIPTION FACTORS that control positional identity of cells (BODY PATTERNING) and MORPHOGENESIS throughout development. Their sequences contain a 180 nucleotide sequence designated the homeobox, so called because mutations of these genes often results in homeotic transformations, in which one body structure replaces another. The proteins encoded by homeobox genes are called HOMEODOMAIN PROTEINS.Transcription Factors: Endogenous substances, usually proteins, which are effective in the initiation, stimulation, or termination of the genetic transcription process.Cambium: A layer of living cells between the bark and hardwood that each year produces additional wood and bark cells, forming concentric growth rings.Polypodiaceae: The fern plant family of the order Polypodiales, class Filicopsida, division Pteridophyta, subkingdom Tracheobionta.Lycopersicon esculentum: A plant species of the family SOLANACEAE, native of South America, widely cultivated for their edible, fleshy, usually red fruit.Plants: Multicellular, eukaryotic life forms of kingdom Plantae (sensu lato), comprising the VIRIDIPLANTAE; RHODOPHYTA; and GLAUCOPHYTA; all of which acquired chloroplasts by direct endosymbiosis of CYANOBACTERIA. They are characterized by a mainly photosynthetic mode of nutrition; essentially unlimited growth at localized regions of cell divisions (MERISTEMS); cellulose within cells providing rigidity; the absence of organs of locomotion; absence of nervous and sensory systems; and an alternation of haploid and diploid generations.Photoperiod: The time period of daily exposure that an organism receives from daylight or artificial light. It is believed that photoperiodic responses may affect the control of energy balance and thermoregulation.Sequence Homology, Amino Acid: The degree of similarity between sequences of amino acids. This information is useful for the analyzing genetic relatedness of proteins and species.Botany: The study of the origin, structure, development, growth, function, genetics, and reproduction of plants.Plant Physiological Phenomena: The physiological processes, properties, and states characteristic of plants.Antirrhinum: A plant genus of the family Plantaginaceae. Members contain DEFICIENS PROTEIN.