Question Video: Identifying the Tissues That Make up the Vascular Bundle | Nagwa Question Video: Identifying the Tissues That Make up the Vascular Bundle | Nagwa

Question Video: Identifying the Tissues That Make up the Vascular Bundle Biology • Second Year of Secondary School

Which two tissues, involved in transport, make up the vascular bundle in plant stems?

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Video Transcript

Which two tissues, involved in transport, make up the vascular bundle in plant stems? (A) Xylem and pith, (B) parenchyma and epidermis, (C) phloem and cortex, or (D) xylem and phloem.

This question asks us to identify the two tissues, which are involved in transport, that make up the vascular bundle in plant stems. Let’s take a look at some of the structures found within a typical dicot stem and discuss their functions. It’s worth noting that monocot plant stems have a slightly different structure.

The outermost layer of cells in the plant stem, and also in their leaves, roots, and flowers, is called the epidermis. The epidermis forms a protective boundary between the plant’s inner tissues and the external environment.

Moving inward from the epidermis are several layers of spongy tissues that make up a region called the cortex, consisting of parenchyma and collenchyma tissues. The majority of the cortex is made up of soft, fleshy parenchyma tissue. The cells in parenchyma tissues have plenty of air spaces between them to promote gas exchange and chloroplasts to carry out photosynthesis. The collenchyma tissue in the cortex is found directly below the epidermis of growing stems. Collenchyma cells have thickened, reinforced cell walls to provide structural support and some flexibility to growing regions of the plant.

We can also see several vascular bundles in this diagram, which make up the plant’s transport system and are of interest to us in this question. One vascular bundle has been circled in orange. Each vascular bundle contains phloem tissue and xylem tissue. Phloem is responsible for transporting sugars and amino acids up and down the plant stem, primarily from the leaves, as this is where most of them will be produced, to the different parts of the plant that require them. Xylem is responsible for transporting water and some dissolved mineral ions up the stem from the roots to all the other parts of the plant.

This means that we have found the tissues involved in transport that make up the vascular bundle in plant stems and, therefore, the correct answer to this question. The two tissues that make up the vascular bundles are (D) xylem and phloem.

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