2. Legumes (Pulses)
• Latin word “legere” = to gather
• family Leguminosae ( Fabaceae)
• consist of :
- 750 genera
- 19,000 species of herbs, shrubs,
trees, and climbers
3. • Four (4) subfamilies:
▫ Papilionoideae
▫ Caesalpinoideae
▫ Mimosaideae
▫ Zwartzioideae (small subfamily of about
80 species and relatively unimportant
economically)
13. • But not all produce nodules
Ex. Subfamilies of: Caesalpinia, Cassia,
and Bauhinia
• Highest incidence of nodulation appears in
Papilionoideae followed by Mimosoideae
15. c) Distinctive flowers
and pods
-Flowers are bilaterally
symmetrical
-Seeds rich in oil (up
to 50%) and protein
(e.g. 15-50%)
16. • Best identified by their reproductive structures
1.front view of flower of Pisum sativum
(pea);
2. petals of P. sativum;
3. flower of Psophocarpus tetragonolobus
(winged bean);
4. flower of P. tetragonolobus in
longitudinal section. a-posterior or
standard petal; b-lateral petal; c-keel
petals (carina); d-sepals; e-stigma;
f-style; g-anther; h-filament; i-ovary wall;
jovule
Figure 2-1. Subfamily Papilionoideae
23. Figure_.Subfamily Caesalpinoideae.
1. bud of Cassia sp.;
2. flower of Cassia sp.;
3. longitudinal section of Delonix regia
(Flame of the Forest or Poinciana)
a-petal;
c-stigma;
e-filament;
b-sepal;
d-style;
f-anther;
g-anther of staminoid;
h-posterior or standard petal;
i-ovary wall;
j ovule.
45. Nutritional value
• Legumes rich in protein (20-30%) N
• contain some fats but usually less
starches than cereal grains
• Has more amino acid composition
which differ from cereal grains
46. Nutritional value
• High fiber levels
• Isoflavones –lower cholesterol levels
• Seeds of almost all legumes are toxic if
eaten uncooked due to proteins or
peptides that inhibit digestive enzymes
(Alkaloids, cyanogens)
47. A Poisonous Legume
Abrus precatorius – Precatory Bean
Abrin – toxin, one of most
toxic substances known
1 crushed seed can be
fatal if ingested
53. Nitrogen fixation
• Roots form associations with bacteria that
fix atmospheric nitrogen
• Rhizobium species live in root nodules
• provide “free” fertilizer (N)
• Atmospheric N can’t be used unless
absorbed in the form of:
- nitrate (NO3-) or
- ammonium (NH4+)
55. Mungo -24 % protein & rich in
vitamins (e.g. thiamine, ascorbic acid
& mineral salts esp. calcium and
sodium)
• feeds, ornamentals, timber, fuel,
medicine, green manure
• components of farming/cropping
systems
• restores soil fertility
56. • Constraints to Food Legume Production:
1. Social & economic factors
- poverty, tradition, fashion, social status,
ignorance or lack of experience;
- lack of demand/poor prices;
- only a subsidiary crop (less priority)
57. 2. Physical and biological factors
-adaptation ( grown in marginal areas)
-agronomic/management (lack of available
improved cultivars)
-poor land preparation (competition of weeds)
58. - growing crop at inappropriate season of the
year (especially if fitted into cereal-based
cropping system
- pest and diseases
- biological N-fixation
- flower shedding and embryo abscission
59. Characteristics:
1. pod - dehiscent (splits into two)
- indehiscent (called loments)
- others have single seed
ex. Winged seed of narra, dispersed by
wind
60. 2. Ability to fix N or convert atmospheric
N into usable form
- through symbiotic relationship
(bet. legume and bacteria)
- host specific
61. Cross
Inoculation
Group
Rhizobium species Legumes
included
Host genera
Alfalfa group R. melitoti Alfalfa/ sweet
clover
Medicago/Melilotus
Clover group R. trifolii clovers Trifolium
Pea group R. leguminosarum pea Pisum
vetch Vicia
Sweet pea Lathyrus
Bean group R. phaseoli Beans Phaseolus
Lupine group R. lupini Lupines Lupinus
Soybean
group
R. japonicum Soybean Glycine
Table . Host specificity of Rhizobium-legume associations
63. • Symbiotic relationship between
macrosymbiont (usually a legume) and a
microsymbiont (Rhizobium)
• Nodules –site of N fixation
But some legumes fail to nodulate due to:
1. unsuitable condition
2. absense of endophyte (microsymbiont)
64. Table _. Legume species and the amount of
atmospheric N fixed/assimilated per hectare
Legume Species Amont of N fixed
(kg/ha/year)
alfalfa 50-350
peas 30-140
peanuts 88
soybean 100
Forage legume 10-550
65. Biological N fixation:
- microbes fixes 150-250 lbs of N/acre/yr
-Bacteria trap atm. N and transformed to
NH3;
- NH3 combines with organic compounds to
form amino acids and proteins;
- In turn plant supplies CHO and energy for
their metabolism
66. • Biological N fixation pathway:
N = N (atmospheric N)
nitrogenase enzyme
+ 2H
NH = NH (diamide)
+ 2H
NH2 = NH2 (hydrazine)
+ 2H
2NH3 (ammonia)
+ alpha-ketoglutaric acid
amino acids
+ other amino acids
proteins