Download Lecture 2 Grass & Legumes

Grasses
Family - Poaceae
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Poaceae
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family Poaceae (noun) - 1. the
grasses: chiefly herbaceous but some
woody plants including cereals;
bamboo; reeds; sugar cane
Synonyms: Gramineae, family
Gramineae, Graminaceae, family
Graminaceae, Poaceae, grass family
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Link to Poaceae
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•includes food crops, pastures, turf, and important
industrial crops.
•Poaceae is the most important family of food crops,
including the cereals, wheat Triticum, corn Zea and rice
(Oryza).
•Some members of the Poaceae form the dominant
vegetation in warm and temperate regions where the
rainfall does not support trees.
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Features of Poaceae
either annuals or perennials.
 alternate leaves with extended
blades and clasping sheath
 stems, or culms, are normally
hollow and round, and enclosed by
leaf sheaths.
 all species have parallel leaf
venation.
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Features of Poaceae (2)
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flowers form a in a spikelet with a primary
axis called the rachilla
sepals and petals are absent; there are two
glumes or bracts at the base of the
spikelet, and each flower is usually
enclosed in two further bracts, the lemma
and palea.
normally there are three stamens and only
one pistil with two stigma
the ovary is superior and contains one ovule
forming an achene like fruit or caryopsis
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Grass Morphology
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Ligules
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Auricles
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How grasses grow
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New growth in grasses occurs in three different ways,
from three different meristems or zones of growth.
New tillers grow from axillary buds at the base of the
plant,
new leaves grow from apical meristems inside the
stems,
and intercalary meristems are secondary zones of
growth at the base of the internode, sheath and blade.
These are growth regions inserted between mature
tissues.
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Vegetative tiller
A vegetative grass tiller. Leaf 1 is oldest
and leaf 8 is just being exerted. The
enlarged area of the crown shows the
apical meristem that produces the leaves
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Reproductive tiller
A reproductive grass tiller. This
tiller has a stem (or culm) and
seedhead that differs from the tiller
in Figure 1. Intercalary
meristematic tissue at the base of
the leaf blade, near the ligule
(insert), allows for leaf expansion.
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LEGUMES
Family Leguminoseae
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LEGUME
legume , common name for any plant
of the family Leguminosae, which is
called also the pulse, legume, pea, or
bean family.
 Botanically, a legume is the
characteristic fruit of the pulse family
plants, called also leguminous plants.
It is a pod which usually splits along
two sides, with the seeds attached
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Features of Leguminoseae
(Fabaceae)
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Numbering about 650 genera and 17,000
species
The leaves are usually compound;
the fruit is a legume (a type of pod);
and the blossoms may have an irregular
butterflylike (papilionaceous) shape.
Typically, the flowers have 10 stamens, and
the corolla and the calyx are formed of 5
petals and 5 sepals, respectively. Some
species have thorny branches.
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Link to typical legume plant
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Nitrogen fixation
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Why are legumes important?
Each year legume-Rhizobium symbiosis generates more useful nitrogen for plants
than all the nitrogen fertilizers produced industrially -- and the symbiosis provides
just the right amounts of nitrogen at the right time at virtually no cost to the
farmer. This symbiotic nitrogen fixation is very beneficial for two reasons:
•it supplies the legume with nitrogen,
•it can significantly decrease spending on N-containing fertilizers for the
subsequent crops.
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Role of Legumes
Supply nitrogen to grasses
 Increased protein for ruminants
(grasses 6-12%, legumes 15-30%)
 Increased minerals (P & K) for
animals
 Improved digestibility of feed
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Dry matter production per
year
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Grasses 20-30 tonnes/ha
C4 photosynthesis
 Resistant to grazing
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Legumes 15-20 tonnes/ha
C3 photosynthesis
 Less tolerant to grazing
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