Section 1: Nutrients and Transport Preview Bellringer Key Ideas Nutrients Transport of Water Transport of Organic Compounds Summary

Bellringer Ask students to write down three common substances that all cells need to survive. Then, have them write down how they think most plant cells obtain these substances.

Key Ideas What substances do plants need, other than water, carbon dioxide, and oxygen, to survive? How does water move through a vascular plant? How do organic compounds move through a vascular plant?

Nutrients Like all multicellular organisms, plants grow by adding new cells through cell division. Plants use energy from sunlight to make organic compounds. Plants need two raw materials, carbon dioxide and water, to make all of the carbohydrates in their tissues. Plants also need oxygen for cellular respiration.

Nutrients, continued However, carbon dioxide, water, and oxygen do not satisfy all of a plant’s needs for raw materials. Plants also require small amounts of at least 14 mineral nutrients, which are elements absorbed mainly as inorganic ions.

Major Mineral Nutrients Required by Plants

Transport of Water Water and mineral nutrients move up from a plant’s roots to its leaves through xylem. When the stomata (tiny pores) are open, water vapor diffuses out of a leaf. This loss of water vapor from a plant is called transpiration. In most plants, more than 90% of the water taken in by the roots is eventually lost through transpiration.

Visual Concept: Transpiration

Transport of Water, continued A stoma is surrounded by a pair of guard cells that are shaped like two cupped hands. Changes in water pressure within the guard cells cause the stoma to open or close.

Transport of Water in Plant Cells

Transport of Organic Compounds Plants produce organic compounds by the process of photosynthesis, usually within their leaves. Organic compounds move through a plant within the phloem from a source to a sink. A leaf is an example of a source. Actively growing parts, such as root tips and developing fruits, are examples of sinks.

Transport of Organic Compounds, continued The movement of organic compounds within a plant from a source to a sink is called translocation. The pressure-flow model proposed by German botanist Ernst Münch shows how organic compounds move in a plant.

Visual Concept: Translocation

Summary Carbon dioxide, water, and oxygen do not satisfy all of a plant’s needs for raw materials. Plants also require small amounts of at least 14 mineral nutrients, which are elements absorbed mainly as inorganic ions. Water and mineral nutrients move up from a plant’s roots to its leaves through xylem. Organic compounds move through a plant within the phloem from a source to a sink.