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

Referencing records, Referencing Records Unlike the elements in a coll... Referencing Records Unlike the elements in a collection, that are accessed using subscripts, the fields in a record are accessed by name. To reference an individual field, you

Defining and declaring collections, Defining and Declaring Collections T... Defining and Declaring Collections To create the collections, you must define a collection type, and then declare the collections of that type. You can define the VARRAY types a

Declaring and initializing objects in pl/sql, Declaring and Initializing Ob... Declaring and Initializing Objects: An object type is once defined and installed in the schema; you can use it to declare the objects in any PL/SQL, subprogram, block or packa

Use tsql function sql server 2012, I want someone to write a TSQL function ... I want someone to write a TSQL function that returns the name of the ODBC DSN. I will use the queries below, to get information about the connection, but none of these return th

Dbms, DBMS: The answer to this question is of course given in of the t... DBMS: The answer to this question is of course given in of the theory book. This book is concerned with SQL DBMSs and SQL databases in particular. Soon we will be looking a

Bulk fetching - bulk bind performance improvement, Bulk Fetching The i... Bulk Fetching The illustration below shows that you can bulk-fetch from a cursor into one or more collections: DECLARE TYPE NameTab IS TABLE OF emp.ename%TYPE; TYPE S

Opening a cursor variable, Opening a Cursor Variable The OPEN-FOR stat... Opening a Cursor Variable The OPEN-FOR statement relates a cursor variable with the multi-row query, executes the query, and then identifies the result set. The syntax for ope

%type - cursors, %TYPE: This attribute gives the datatype of a formerly... %TYPE: This attribute gives the datatype of a formerly declared collection, cursor variable, object, field, record, database column, or variable. Datatype: This is simply

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

program for employees -ado.net framework , Challenge 1 You are require... Challenge 1 You are required to do the project and write a test plan for it. Demo 4 is a check writer program for employees. In it, the user enters all information about the