Assertion : Long distance flow of photoassimilates in plants occurs through sieve tubes. Reason : Mature sieve tubes have parietal cytoplasm and perforated sieve plates.

Step-by-step solution

The main function of sieve tube is the transport of food products from green and storage organs of the plant to other organs of the plant. The sieve elements are sieve tubes arranged one above the other and have sieve plates (obligue or transverse perforated septa) on their end walls. The cytoplasm occur in the form of a thin living layer along the inner side of cellulose wall. The nucleus disappears in mature sieve elements.