Which of the following is an incorrect statement ?

The correct answer is: Mature sieve tube elements possess a conspicuous nucleus and usual cytoplasmic organelles.

Let us analyze each statement to understand why this statement is incorrect:

1. Mature sieve tube elements and their structure:
Sieve tube elements are specialized conducting cells in the phloem of vascular plants, primarily responsible for the translocation of food (sucrose). During development, as sieve tube elements mature, they undergo a process of selective degeneration (autophagy) where they lose their nucleus, ribosomes, vacuole, and Golgi apparatus. This lack of a nucleus and main organelles reduces resistance to the flow of sap, allowing for efficient transport. Therefore, mature sieve tube elements do not possess a nucleus or usual cytoplasmic organelles. Instead, they rely on adjacent companion cells, which retain their nuclei and organelles, to perform vital metabolic functions for them. This makes the first statement incorrect.

2. Microbodies:
Microbodies (such as peroxisomes, glyoxysomes, and lysosomes) are membrane-bound, minute vesicles containing various enzymes. They are indeed present in both plant and animal cells, making this statement correct.

3. Perinuclear space:
The perinuclear space is the fluid-filled space between the inner and outer nuclear membranes of the nuclear envelope. It acts as a physical barrier separating the genetic material inside the nucleus from the cytoplasm, making this statement correct.

4. Nuclear pores:
Nuclear pores are large protein complexes that span the nuclear envelope. They serve as selective channels allowing the bidirectional movement of proteins (entering the nucleus) and RNA molecules (leaving the nucleus) between the nucleoplasm and the cytoplasm. This statement is correct.