Sieve tubes are specialized structures within the phloem responsible for transporting nutrients. They contain pores called sieve plates through which nutrients flow. Sieve tubes are assisted by adjacent companion cells, which provide metabolic support and help regulate nutrient transport.
What are sieve tubes, and how do they facilitate translocation in the phloem?
Share
Sieve tubes are specialized cells in the phloem of plants responsible for the translocation of organic nutrients, mainly sugars, from source to sink tissues. These elongated cells have perforated end walls called sieve plates. The sieve plates enable the flow of sap containing sugars and other substances between adjacent sieve tube elements. Companion cells, closely associated with sieve tubes, provide metabolic support for sieve tube function. Translocation occurs through a process called pressure flow, driven by osmotic pressure gradients. Sugars move from high-concentration source tissues (like leaves) to lower-concentration sink tissues (such as roots or developing fruits), sustaining plant growth and metabolism.