In some Acacia species, such as the koa tree (Acacia koa), the petioles are expanded or broadened and function like leaf blades; these are called phyllodes. For xerophytes the major constraint is not light flux or intensity, but drought. [19] The terminology associated with the description of leaf morphology is presented, in illustrated form, at Wikibooks. In any square centimeter of a plant leaf, there may be from 1,000 to 100,000 stomata.[15]. Our moderators only check the spelling and punctuation of posted comments. The meaning of several of the following terms can overlap. A pseudo-reticulate venation that is actually a highly modified penniparallel one is an autapomorphy of some Melanthiaceae, which are monocots; e.g., Paris quadrifolia (True-lover's Knot). [41] Long narrow leaves bend more easily than ovate leaf blades of the same area. Other herbivores and their predators mimic the appearance of the leaf. beans and roses), soon falling or otherwise not obvious as in Moraceae or absent altogether as in the Magnoliaceae. [24][23][25], The vein or veins entering the leaf from the petiole are called primary or first-order veins. A structurally complete leaf of an angiosperm consists of a petiole (leaf stalk), a lamina (leaf blade), stipules (small structures located to either side of the base of the petiole) and a sheath. These I-beams are formed from bundle sheath extensions of sclerenchyma meeting stiffened sub-epidermal layers. A vein is made up of a vascular bundle. Download Grammarly's app to help with eliminating grammar errors and finding the right words. These can further develop into either vegetative or reproductive structures. In angiosperms the venation is typically parallel in monocotyledons and forms an interconnecting network in broad-leaved plants. Not every species produces leaves with all of these structural components. A leaf with white patches or edges is called a variegated leaf. The broad, flat leaves with complex venation of flowering plants are known as megaphylls and the species that bear them, the majority, as broad-leaved or megaphyllous plants. There is a regularity in these angles and they follow the numbers in a Fibonacci sequence: 1/2, 2/3, 3/5, 5/8, 8/13, 13/21, 21/34, 34/55, 55/89. Functionally, in addition to carrying out photosynthesis, the leaf is the principal site of transpiration, providing the energy required to draw the transpiration stream up from the roots, and guttation. Typically leaves are broad, flat and thin (dorsiventrally flattened), thereby maximising the surface area directly exposed to light and enabling the light to penetrate the tissues and reach the chloroplasts, thus promoting photosynthesis. Leaves can also store food and water, and are modified accordingly to meet these functions, for example in the leaves of succulent plants and in bulb scales. [59], An older, even simpler system, used in some flora[60] uses only two categories, open and closed. Open: Higher order veins have free endings among the cells and are more characteristic of non-monocotyledon angiosperms. There are several other words ending in "f" that change to "v" for the plural. "Leaves" is the plural of "leaf." [11] Some window plants such as Fenestraria species and some Haworthia species such as Haworthia tesselata and Haworthia truncata are examples of xerophytes. In the clubmosses, with different evolutionary origins, the leaves are simple (with only a single vein) and are known as microphylls. Copyright © WhichIsCorrect.com 2013-2020. Monocots typically have such linear leaves that maximize surface area while minimising self-shading. Hij staat onder contract bij het platenlabel Noah's Ark.