BotanicalBotanical LessonsLessons Plant organisation (1/2) Leaves of the family Crassulaceae (here the Potatoes are stems that have been modified to 53 example of the houseleek, Sempervivum store nutrient reserves. In common with all stems, montanum) can store water as an adaptation they carry the buds ("eyes") to drought Flowering plants are composed of three parts: roots, stems and leaves. blade veins Roots. Most often found underground, roots anchor plants to the soil and absorb water and mineral elements required for growth. They can be either taproots (a single vertical root) or fasciculate. Sometimes roots also store reserves (such as in the carrot). petiole stipules alternate opposite The stem. Generally found aboveground, stems carry the buds, which determine the growth, General organisation of a leaf and examples of ramification and flowering of the plant. Stems maintain the plant upright and are essential for the the arrangements "alternate" and "opposite" transport of nutrients (sap). Stems can be herbaceous, or rigid and lignified (wood) in shrubs and trees. Diagram of a plant: roots (in black, here fasciculate, with numerous roots attached to the same point), stem (in brown), leaves (in Leaves. Leaves are the principal organ of photosynthesis and transpiration. They generally green) and a flower (in blue). The stolons are lanceolate ovate obovate orbicular above ground stems which grow horizontally comprise of two parts: the lamina and the petiole. The lamina is a flattened blade containing veins and produce clones of the mother plant. which transport the sap. The shape, margin and pattern of veins differ between species and constitute criteria for identification. The lamina is divided into leaflets, in the case of leaves called sagittate pedate pennatilobate cordate “compound” leaves. The petiole, which is sometimes absent, attaches the leaf to the stem. Phyllotaxy describes the arrangement of leaves on the stem. Leaves can, for example, be grouped in pairs attached face to face along the stem (leaves called "opposite") or be rather isolated and palmate paripennate imparipennate An example of a plant with both an A few examples of the diversity of leaf blades. In underground stem, or rhizome (in brown), and brown, the petiole, in dark green, some an above ground stem; the roots (in black) are arranged regularly in a spiral around the stem (leaves called "alternate"). examples of "compound" leaves called “adventive” (newly formed on the stem) BotanicalBotanical LessonsLessons Plant organisation (2/2) Two gentians: Gentianella campestris (left, The daffodil (Narcissus poeticus, 53 hemicryptophyte) and Gentiana nivalis (right, a Amaryllidaceae family), an example of a rare alpine therophyte) cryptophyte plant with a bulb The Danish botanist Christen Raunkiær (1860-1938) developed a classification of plants founded on A. Phanerophytes (trees, shrubs > 50 cm) their strategies to survive bad winter conditions. This classification is based on the position of plant Perennial B. Chamephytes subshrubs (a), creeping shrubs (b), plants with woody basee (c) buds during the winter. Phanerophytes are trees and shrubs higher than 50 cm. Their buds are not plants C. Hemicryptophytes rosettes (d), tufts (e) protected from frost by snow cover, which is one of the reasons that trees are absent from the alpine D. Cryptophytes (ou geophytes) with rhizome (f), or bulb (g) zone. Chamephytes are small shrubs whose buds are sufficiently low to be protected by snow cover. Annual E. Therophytes Numerous cushion plants from dry mountain areas (see the rockery “Spanish mountains”) have plants woody bases and also belong to this category. Hemicryptophytes have their buds located at soil A CD level, and their leaves form either a rosette (such as the Dandelion) or a tussock (such as in numerous e f Poaceae or Cyperaceae). Cryptophytes (also called Geophytes) have their buds buried, and thus 50 cm B E g protected from cold under the ground (geo in Greek). The buds are situated on the rhizomes a cd b (underground stems) or on bulbs which accumulate reserves to fuel the beginning of growth for the next year. Therophytes are annual species. These species pass the winter period as seeds, highly resistant to aridity and frost. Very common in arid areas, annual species are almost non-existent in alpine areas, mostly because of the highly random nature of the possibility for sexual reproduction at high altitudes. The principal "biological types" based on the position of the buds during winter (in red). In black, the perennial parts of the plant that remain from one year to the next; dotted lines, the plant parts that die during the winter. Etymology of the terms: "phanero", visible; "chamae", dwarf; "hemi", half; "crypto", hidden; "thero", summer. BotanicalBotanical LessonsLessons The concept of the alpine plant (1/2) The mountain avens (Dryas octopetala, The gentians (here Gentiana acaulis, 53 Rosaceae family), an example of an Gentianaceae family), examples of plants arctic-alpine plant originating from the Himalayan region Altitudinal vegetation zones. Mountain vegetation is divided into zones, each with a characteristic type of vegetation. The upper limit of the sub alpine zone marks the natural limit (without human intervention) of trees. This limit is found around 2300 m altitude in the Alps. Higher up is found the alpine South North zone where environmental conditions become more and more extreme with altitude due to decreasing mean temperatures, increasing solar radiation, strong winds, etc. The sub alpine / alpine NIVAL belt boundary varies from 0 m altitude in polar areas, up to above 4000 m in tropical regions. For biologists, mosses, lichens 3000 m ADRET UBAC 2900 m an alpine plant is a species that grows in the alpine zone, in the Alps or another mountain region. Routes of the plant colonisation of the Alps: 1, Mediterranean; 2, Central Asian; 3, Arctic ALPINE belt Determined mostly by temperature, the limit of the alpine zone is rising due to global warming, 2400 m alpine meadows endangering those plants that grow at high altitudes. The plants growing in the Lautaret alpine garden 2200 m come from subalpine and alpine zones. Etage SUBALPIN 1700 m conifer forests Multiple origins for the flora of the Alps. The current alpine flora is the result of a colonisation begun some 1500 m 10 000 years after the retreat of the glaciers. The major vegetation influences come from the MOUNTAIN belt 1100 m mixed forests Mediterranean, Central Asian (notably Himalayan) and arctic regions. In the case of the arctic region, 900 m the alternation between glaciations and glacial retreat has contributed to numerous exchanges of COLLINEAN belt flora, resulting in the presence of numerous plant species, called arctic-alpine species, which are found The campanulas (here Campanula alpestris, broadleaved forests Campanulaceae family), a plant with a both in the Alps and in arctic regions. Mediterranean origin BotanicalBotanical LessonsLessons The concept of the alpine plant (2/2) Swiss androsace (Androsace helvetica, High altitude Dwarf willow (Salix serpyllifolia, 53 Primulaceae family), a cushion plant growing Salicaceae family) an example of a prostrate amongst rocks at the Galibier pass (around 2800 m) plant Morphological adaptations. A small size is very common amongst alpine plants, allowing them to at the surface 25 of the cushion remain within 1 to 2 m of the ground where temperatures are less cold. It also allows plants to benefit 20 from protection by snow cover in winter, and limits the mechanical effects of the wind and snow which 15 10 can break stems and branches. Cushion plants are a well-known example of adaptation to extreme at 2 m Temperature(°C) from the cushion 5 conditions: the cushion functions as a heat trap as its geometric form exposes the least surface area to 0 9 12 15 18 external conditions, limiting both losses of heat (and water). Plant hairs are another adaptation: these Hour of the day (summer) form a screen that protects the plant from cold, dry and strong solar radiation. Root systems of alpine The temperature difference between the surface of a cushion plant and at two meters plants can also exhibit adaptations, such as the presence of a long tap root in cushion plants. Structure of the Swiss androsace, an example of height (using the example of silene acaule) a cushion plant with a long tap root alpine plants Physiological adaptations. Alpine plants synthesise molecules (sugars, anti-freeze proteins) which 5 protect their cell membranes from the effects of freezing. They can also maintain their cell contents in 4 a liquid state down to temperatures of -40°C. To counter oxidative stress imposed by excessive solar 3 lowland plants 2 radiation (light and UV), plant can accumulate anti-oxidants, in particular vitamin C. These 1 Vitamin C, micromol/mg chlorophylll micromol/mg C, Vitamin adaptations are the results of long periods of evolution. They are in part fixed in the genetic makeup of 0 132 465 alpine species, and in part dependant on environmental conditions (acclimation). Differences in the concentration of vitamin C in three alpine plants (1, soldanella; 2, alpine coltsfoot; 3, glacier ranunculus) and three Ces adaptations sont le fruit d'une longue évolution. Elles sont pour partie inscrites dans le patrimoine The edelweiss (Leontopodium alpinum, lowland plants (1, rye; 2, dandelion; 3, Asteraceae family), an example of a plant meadow buttercup) génétique des espèces et pour partie conditionnées par les conditions environnementales (acclimatation). covered with protective hairs BotanicalBotanical LessonsLessons Interspecific relationships (1/2) Mont Cenis restharrow (Ononis cenisia, Lousewort (Pedicularis comosa, Orobanchaceae 53 Fabaceae family), an example of a plant family), an example of a hemiparasitic plant able to fix atmospheric nitrogen atmospheric nitrogen (N2) Plants have multiple types of relationships between each other, and with other organisms (bacteria, animals). Here are a few examples organic nitrogen Symbiosis. This is a long term association between two organisms allowing each to obtain (proteins) root reciprocal advantages.