PITS

• Depressions in secondary cell wall is called pit.
• A pit present on the free cell wall surface without its partner is called Blind pit.
• It consists of 2 parts - Pit chamber and Pit membrane.
• Pit chamber / pit cavity is depression in wall where secondary wall is absent.
• Opening of pit chamber into cell is called pit pore / aperture.
• Pit membrane is formed of (PCW + middle lamella + PCW) it is "trilaminar".
• Pit membrane also called closing membrane.
• Pit membrane is permeable due to permeability of primary cell wall.
• Pits are of 2 types (depending upon the shape of the pit chamber.)

(i) Simple pit

• Pit chamber has uniform width.
• Diameter of lumen remains the same.
• Found in vessels, tracheids & sclerenchyma.

(ii) Bordered pit

• Pit chamber is flask-shaped.
• Diameter of lumen is increases from inner to outer side.
• A disc-shaped thickening called Torus is present in the middle of pit chamber on pit membrane.
• It controls diffusion, it prevents rupturing of pit membrane when unequal pressure is present on its both sides.

Posted Date: 10/5/2012 6:03:23 AM | Location : United States

Ask an Expert

Related Discussions:- Pits, Assignment Help, Ask Question on Pits, Get Answer, Expert's Help, Pits Discussions

Write discussion on Pits
Your posts are moderated

Write your message here..

Related Questions

Pascal programming and mysql programming, I have a Pascal Source file that ... I have a Pascal Source file that needs to be compiled into a Service. In addition, there are various functions (Pascal Procedures I guess) that need to be created to Read and Write

I want database development with analysis tools, Project Description: I ... Project Description: I want a database for large governmental and private data sets on one country that will be easily extended to other countries in the future. Also, the datab

Recursion versus iteration, Recursion versus Iteration Dissimilar the i... Recursion versus Iteration Dissimilar the iteration, recursion is not crucial to PL/SQL programming. Any problem which can be solved using recursion can be solving using the it

Nested tables versus index-by tables, Nested Tables versus Index-by Tables ... Nested Tables versus Index-by Tables The Index-by tables and nested tables are just similar. For e.g.  They have similar structure and their individual elements are accessed in

How bulk bind helps improvement in performance?, How Bulk Binds Improve Per... How Bulk Binds Improve Performance The assigning of values to the PL/SQL variables in SQL statements is known as binding. The binding of the whole collection at once is know

Fetch statement - syntax, FETCH Statement The FETCH statement retrieve ... FETCH Statement The FETCH statement retrieve rows of data one at a time from the result set of the multi-row query. The data is stored in fields or variables which correspond t

Example of delete - sql, Example of DELETE - SQL As with UPDATE, a FOR... Example of DELETE - SQL As with UPDATE, a FOR PORTION OF clause can be specified if the target table has a defined period name, as illustrated in Example. Example: Deleting

Commit statement in pl sql, COMMIT Statement The COMMIT statement expli... COMMIT Statement The COMMIT statement explicitly makes everlasting changes to the database during the present transaction. The Changes made to the database are not considered e

Relational algebra - sql, Relational Algebra - SQL It describes some ... Relational Algebra - SQL It describes some operators, that together constitute an algebra that is not only relationally complete but also irreducibly so (very nearly- apart f

Effects of null, Effects of NULL The numeric variable X, perhaps of ty... Effects of NULL The numeric variable X, perhaps of type INTEGER, might be assigned NULL. In that case the result of evaluating X + 1 is NULL, and so SET Y = X + 1 assigns NULL