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 6:02:54 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
Semijoin and Composition - SQL For semijoin, the dyadic relational operator MATCHING, defined thus: r1 MATCHING r2, where r1 and r2 are relations such that r1 JOIN r2 is de

Autonomous versus Nested Transactions Though an autonomous transaction is started by the other transaction, it is not a nested transaction for the reasons shown below: (i)

THEORY OF BIOGENESIS - This theory explains that the existing living organisms originated from pre-existing living beings not from non living entities. This concept of or

Advantages of Exceptions Using the exceptions for the error handling has many benefits. Without an exception handling, every time you issue a command, you should ensure for th

Main features of PL/SQL A good way to get familiar with PL/SQL is to look at a sample program. The below program processes an order for tennis rackets. At first, it declares a

Extension and AND in SQL The theory book gives the following simple example of relational extension in Tutorial D: EXTEND IS_CALLED ADD ( FirstLetter ( Name ) AS Initial )

BETWEEN Operator The operator BETWEEN, tests whether the value lies in a specified series. That means "greater than or equivalent to low value and less than or equivalent to hig

Use of Table Comparisons - SQL Table comparisons where it is noted that although table expressions cannot be compared, we have TABLE (t) to convert a table expression t into

We are seeking a freelance consultant that is familiar with Appgen applications. We require exporting all our data into a format appropriate for importing into SAP Business One. Pl

Using %TYPE The %TYPE attribute gives the datatype of a variable or the database column. In the example below, the %TYPE gives the datatype of a variable: credit REAL(7,2); debi