The Leaf Epidermis

By Author: seolncr plumstech
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The guttation, observable phenomenon as water droplets on the leaf epidermis, occurs when the plant is under conditions favoring rapid absorption of water and minerals and a minimum sweat, like plants growing in moist soil during the overnight. The mineral ions absorbed at night are pumped to the apoplast surrounding the elements of the xylem . This loss of solutes lowers the water potential in xylem elements, generating revenue of water from the surrounding cells. By increasing the pressure inside the xylem water is eventually forced out through the leaf hydathodes.
Hydathodes are distributed in many species of angiosperms (350 genera belonging to 115 botanical families). In tropical plants like Colocasia ( Araceae ), the amount removed per night more than 300 ml of water.

The hydathodes are of two types:
Liabilities, such as Gramineae , which remove water by osmosis when the pressure radical.
Active most hydathodes epitémicos ( Tropaeolum , Saxifraga ) and tricómicos ( Cicer , Phaseolus ) ; glands are working independently of the pressure radical.
Hydathodes tricómicos epidermal or secrete ...
... an aqueous solution with some organic or inorganic compounds (eccrine secretion, metal ion pumped through the plasma membrane).
In young leaves and stems of Cicer arietinum epidermal hydathodes consist of a uniseriate stalk and a multicellular head oval. The solution is accumulated under the cuticle and when it reaches a certain volume open pores in the cuticle and droplets on the surface appear. The presence of numerous mitochondria indicates that secretion is active.
Epitémicos hydathodes have a specialized parenchymatous tissue, the epitema , located at the end of one or more sheets venules. Epitema Surrounding the sheath cell is a tightly arranged, often with adjacent walls cutinized, forming a type endodermal layer, which prevents backflow apoplastic. Many of these cells are differentiated as transfer cells. Outwards, the epitema is limited by the epidermis, and the output of water occurs through one or more modified stomata, which differ because the guard cells usually can not close the ostiole.

In Botany , it is called laticiferous to that structure that secretes latex juice, thick, creamy, usually milky-white appearance (as in Euphorbia ). It can also be transparent in Allium or take other colors (yellow and in Argemone ).
The role of laticifers is not clear, could be an internal system of excretion, or defense. The secretion is intracellular. The nature of the latex is varied, the aqueous matrix can grains of starch , glass, etc..
There laticifers in a genre of Pteridophyta ( Regnellidium ) and about 12,500 species of 900 genera of dicots and monocots . Are characteristic of several families, such as: Asclepiadaceae , Apocynaceae , Caricaceae , Euphorbiaceae and Papaveraceae .

They are a very heterogeneous group, not only from a metabolic point of view but also from the point of view of its anatomy and ontogeny . They are classified into two types: those that are made ??from a single cell (called non-articulated ) and those formed by many cells (called articulated ).

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