Leaves are the principle photosynthetic organs of higher plants. • Roots are
hidden but may account for 1/3 of the total plant weight. Vegetative Anatomy.
Vegetative Anatomy of Crop Plants
Thomas G Chastain CROP 200 Crop Ecology and Morphology
Vegetative Anatomy • Stems provide support for leaves, flowers, and fruit. The shoot system is made up of stems and leaves. • Leaves are the principle photosynthetic organs of higher plants. • Roots are hidden but may account for 1/3 of the total plant weight.
Shoot and root system of a tall fescue plant
Leaf • Simple Leaves - Leaves with one blade are known as simple leaves. • The blade of a leaf is known as the the lamina. • The support stalk of a leaf is called a petiole. • When the leaf has no petiole it is known as a sessile leaf.
Examples of simple leaves, young canola plant (top), and cucumber (bottom)TG Chastain photos
Lamina
Petiole
Leaflet
Petiolar Branch
Petiole Potato leaf (TG Chastain photo)
Leaf • Compound Leaves - Leaves with two or more blades are called compound leaves. • Each blade on a compound leaf is called a leaflet. • The stalk of a leaflet is called a petiolule or petiolar branch.
Leaflet Tendril
Stipule
Leaf • Compound Leaves - When the compound leaf has three leaflets it is known as a trifoliolate. Many legumes have this type of leaf. • The stipule is a leaf-like growth found at the base of the petiole.
Stem Trifoliolate Pea leaf and stipule (TG Chastain photos)
Stems and Branches • Function of stems and branches: 1. Provide support for leaves, flowers, and fruit. 2. Connect leaves, flowers, and fruit with water and nutrients moving up from the root. Connect roots with above-ground food producing (photosynthetic) organs. 3. Carbohydrate storage. 4. Carbohydrate production via photosynthesis. Canola stems (top), sunflower main stem and branches (left). TG Chastain photos
Stems and Branches Kentucky bluegrass plant, stolon (bottom right) TG Chastain photos
Leaf
Tiller
Rhizome
Mainstem
Roots
• The tiller is a branch on a grass plant. • Rhizomes are specialized stems which grow horizontally below the soil surface and eventually turn upward. At the point where the rhizome emerges from the soil, a new plant, genetically identical to the parent plant is formed. • Stolons are horizontal, aboveground stems.
INTERNODE
Grass stem and leaf structure (top), corn stem and leaf (right) TG Chastain photo
Stems and Branches • The node is the part of the stem where the leaves are attached. • The internode is the region between the nodes.
Stems and Branches • The shoot apical meristem or SAM and the intercalary meristem are the two primary sites of stem growth and developmental activities. • In dicots, stem development and branching results from the activity of the apical meristem. Typical SAM of dicots
Stems and Branches • The shoot apical meristem in monocots, such as the grasses, is hidden within the stem and is the source of new leaves and tillers. • The crown is the part of the plant where the shoot system (tillers) meets the roots.
Tiller Crown Roots
Location of SAM in grasses (top left), crown of grass plant (bottom left) TG Chastain photo
Stems and Branches • The intercalary meristem is responsible for the elongation of the stem (internode) and is located at the base of the internode region.
Time
Longitudinal section of grass stem showing location of intercalary meristem and it’s impact on stem elongation in grasses
Stems and Branches • Tubers are not roots, they originate from stolon tips. Tubers are important organs for the storage of starch.
Stolon
New Tuber
Potato tuber (top), stolon with developing tuber (bottom) TG Chastain photos.
Roots • The primary functions of plant roots are to: 1. Anchor the plant 2. Absorption of water and nutrients 3. Food storage
Grass roots with root hairs (TG Chastain photo)
Roots • In some crop plants, roots are a strong sink for the accumulation of carbohydrates and are the unit of economic yield for which the crop is managed. • Examples include carrot, radish, yam, and beet.
Root Development
Secondary roots
Primary root
• The first root to develop from the apical meristem at the root end of the embryo (radicle) is known as the primary root or taproot. • In dicots, the taproot axis and the branched secondary roots (laterals) make up the root system. This pattern of root development forms a taproot system.
Root Development
• In monocots, the primary root is short lived and the root system is formed by adventitious roots arising from the shoot. This type of root development forms a fibrous root system. • Seminal roots arise from 2 nodes in the seed. These include the primary root axis (arising from the radicle) and up to 5 other root axes. • Crown or nodal roots are associated with tillers and the mainstem.
