Pits, PL-SQL Programming

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.)

1318_pits.png

(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.

1106_pits 1.png

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







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

Write discussion on Pits
Your posts are moderated
Related Questions
SQL Cursor   The Oracle implicitly opens a cursor to process each SQL statement not related with an explicit cursor. The PL/SQL refers to the most current implicit cursor as t

Brewbean's is implementing a new discount for return shoppers - every fifth completed order receives a 10% discount. The count of orders for a shopper is placed in a packaged varia

Write a stored procedure that accepts the post code in which the customer resides as the input parameter. The procedure should then use an explicit cursor to display comprehensive

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

Parameter and Keyword Description:   table_reference: This identifies a table or view which should be available when you execute the INSERT statement, and for that you sho

What Is a Package? The package is a schema object that group logically related PL/SQL items, types, and subprograms. The Packages usually have 2 parts, a specification & a bo

%ROWCOUNT The %ROWCOUNT yields the number of rows affected by the INSERT, UPDATE, or DELETE statement, or returned by a SELECT INTO statement. The %ROWCOUNT yields zero when a

Forward Declarations The PL/SQL needs that you declare an identifier before using it. And hence, you should declare a subprogram before calling it. For illustration, the decla

Built-In Functions The PL/SQL provides a lot of powerful functions to help you to manipulate the data. These built-in functions fall into the categories as shown below: error r

SQL Operators The PL/SQL uses all the SQL set, comparison, and row operators in the SQL statements. This part briefly describes some of these operators.  1. Comparison Opera