Q.65 Sieve-tube elements found in Angiosperms are

1. Sieve tube
2. P-protein present
3. P-protein absent
4. Sieve-plate
5. Companion cells

Choose the correct answer from the options given below :

1. A, B, D, E only
2. A, C, D, E only
3. A, B, C, D, E only
4. A, B, E only

   A, C, D, E only is the correct answer for sieve-tube elements in angiosperms. These living phloem cells form sieve tubes, lack P-protein, feature sieve plates, and associate with companion cells, excluding P-protein presence as a characteristic.

   Sieve-Tube Element Structure

   Sieve-tube elements stack end-to-end in angiosperm phloem to conduct sugars. Mature forms lack nuclei and ribosomes but retain thin cytoplasm and plasma membranes.

   Feature Analysis

   • Sieve tube (A): Correct—these elements collectively form sieve tubes via end-to-end alignment.

   • P-protein present (B): Incorrect—P-protein (phloem protein) occurs mainly in sieve elements of minor veins or Fabaceae; absent or minimal in most angiosperm sieve-tube elements, which use callose plugs for sealing.​

   • P-protein absent (C): Correct—mature sieve-tube elements typically lack P-protein.

   • Sieve-plate (D): Correct—end walls bear specialized sieve plates with large pores (>1 μm) distinguishing angiosperms from gymnosperm sieve cells.

   • Companion cells (E): Correct—densely cytoplasmic cells connected via plasmodesmata provide metabolic support to enucleate sieve-tube elements.

   Option Breakdown

   Option	Features Included	Why Valid/Invalid	Correct?
   A, B, D, E only	Sieve tube, P-protein present, Sieve-plate, Companion cells	Includes erroneous P-protein presence.	No ​
   A, C, D, E only	Sieve tube, P-protein absent, Sieve-plate, Companion cells	Matches angiosperm characteristics excluding P-protein.	Yes
   A, B, C, D, E only	All features	Claims contradictory P-protein presence/absence.	No ​
   A, B, E only	Sieve tube, P-protein present, Companion cells	Omits sieve plates; wrong on P-protein.	No ​

   Sieve-tube elements angiosperms lack P-protein but contain sieve-plates and companion cells, forming efficient phloem transport systems crucial for GATE Life Sciences plant anatomy mastery.

   Defining Features

   Elongated cells align into sieve tubes ending in porous sieve plates; companion cells sustain function.​

   P-Protein Clarification

   Absent in mature general sieve-tube elements (unlike minor veins); callose seals wounds instead.​

   Exam Focus

   Option 2 excludes P-protein presence, matching angiosperm phloem specialization.​