Introduction

Grass structure

Legume structure - non-spreading

Legume structure - vegetatively spreading

Meristems

Farm Management

Introduction

	Morphology = "morphe" (Greek for form) + "ology" (to study)
	plant morphology - physical characteristics of plants are the components of yield (e.g. number of tillers, number of leaves, size of leaves)
	plant morphology is the basis for plant identification - especially flower heads and seed pods
	an understanding of plant morphology allows us to understand aspects of plant response to management and the environment
	allows us to have a standardized descriptive terminology

Grass Structure

The basic unit of grass growth is a tiller. A tiller comprises leaves (usually around 3), emerging from a leaf sheath, and roots. A bunch grass plant is a collection of tillers e.g. ryegrass, orchardgrass, smooth bromegrass. Sod-forming grasses also produce above-ground 'creeping' stems (stolons) e.g. Kentucky bluegrass or creeping bentgrass, or under-ground stems (rhizomes) e.g. reed canarygrass, quackgrass The growing point of the tiller is at ground level - and generally protected from mowing or grazing.

Parts of a grass plant click to enlarge (142kb)

The most common legume plant structure e.g. alfalfa or red clover. Common structure for most weeds e.g. red root, annual thistles, ragweed (rely on seed spread) no mechanism of vegetative spread plant crowns are sensitive to damage by tractors, frost heaving and cattle treading. Damaged plants are prone to being infected by fungal pathogens, ultimately resulting in plant death. After harvest, plants need to regrow from meristematic areas on the plant crown.

Parts of a legume plant click to enlarge (91kb)

  Vegetatively-spreading forage legumes

The dominant plant structure for 'creeping' plants. stolons - above ground stems e.g. white clover, alsike clover. rhizomes e.g. kura clover, Canadian thistle plants have the capacity to grow rapidly into gaps in the pasture. nodes can produce roots, and eventually can become independent plants if the stolon is broken by treading or eventually senescences. Meristems in the axis of leaves (petioles) can produce flowers or a new branch - thus the potential for vegetative or reproductive growth.

Vegetatively spreading forages click to enlarge (44kb)

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Meristems (pg 27)

Meristems are the origin of new plant growth - undifferentiated cells from which leaf and stem structures develop. Areas of intense cell division. By the time a leaf appears, cell division has stopped and leaf growth is largely by cell expansion (water dependant phenomenon). In grasses the meristems are at the base of the tiller (ground level). New leaves emerge from the center of the tiller. Leaves emerge at a fairly constant rate even if the grass is cut or grazed. In legumes (e.g. alfalfa) meristems are at the end of the stems, so once the crop is cut, new stems must regrow from the plant crown.

Cross section of a forage meristem click to enlarge (56kb)

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Implications for Farm Management

Understanding the morphological components of plants is the key to managing forage quality (ratio of leaf:pseudo stem, identifying the onset of flowering (boot stage) in a crop. Cutting too late will reduce quality and subsequent yield. The morphological trait most closely associated with crop yield is leaf length (stand height). Experienced farmers can estimate stand yield based on height. The sward stick and rising plate meter are two tools for measuring yield, and this is based on stand height. Meristems are the basis of all new growth. Damaging meristems by tractors or hooves, especially when soils are wet and for non-spreading forages (alfalfa) Being able to identify your forages is dependant on a thorough knowledge of plant morphology.

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