Pg.no. 42
13. Vascular Tissue
Definition
Vascular tissue is an arrangement of multiple cell types in vascular plants which allows for
the transport of water, minerals, and products of photosynthesis to be transported throughout
the plant. Non-vascular plants , such as some algae and moss, do not have vascular tissue and
therefore cannot easily transport water and
nutrients. Vascular plants use their vascular
tissue to transport water and nutrients to
great heights, able to feed the tops of trees
hundreds of feet high.
Types of Vascular Tissue
Xylem
Xylem is a specialized type of vascular
tissue created in vascular plants to transport
water and nutrients from the roots of a plant
to the tips of the leaves. Every cell in the
plant needs water and minerals to survive,
and complete necessary reactions. The xylem is created from hollow, dead cells. Water is
absorbed into the roots, which creates a positive pressure on the water inside the column. As
water evaporates out of the leaves, the process of transpiration pulls water into the leaves. In
this way, the xylem serves as a straw, allowing water to carry minerals upwards through the
plant.
Figure 13.1 (Vascular Tissue)
Phloem
At the same time, the plant is producing sugars via photosynthesis , which must be
transported downwards, to the stem and root cells. Another vascular tissue, the phloem ,
accounts for this process. Unlike the xylem, this vascular tissue is made up of living cells.
The so-called sieve cell are connected via a thin membrane called the sieve plate . Through
this channel of phloem cells sugar is transported throughout the plant. Unlike water, sugar is
thick and sappy. The phloem requires inputs of water from the xylem and specialized
proteins to help quickly pass the sugars through the plant.
Structure of Vascular Tissue
In different species of plants, vascular tissue is arranged differently. Typically, the cells are
long, narrow, and tubular. The vascular tissue is also often arranged into bundles within the
stem or leaf. Below is a comparison of the vascular tissue found in monocot and dicot plants.