Transcript RLO 7

RLO Title
Role and deficiency/toxicity
symptom of micronutrient in rice
Contributor/Co-contributor & affiliation :
Dr D.K.Borah, Professor & Head,
Department of Soil Science, Assam Agricultural University,
Jorhat-785013
Key words : Micronutrient,deficiency, toxicity,symptom,
chlorosis
Complexity level : Simple
End user: Farmer
Duration of RLO: 15 minutes
Language: English
Learning objective
Help identification of deficiency/toxicity
symptom of micronutrient in rice
Abstract
Micronutrients are those nutrients which are required for
the growth and development of plant. These nutrients
are mostly iron, manganese, zinc, copper, boron,
molybdenum and chlorine. Out of these, chlorine
deficiency and toxicity is not generally observed in
plants as this micronutrient is supplied indirectly from
various sources.Though these nutrients are required in
small quantity but deficiency of it may retard growth and
development of plant
Content
Micronutrient Deficiency/ Toxicity in rice
Micronutrients are those nutrients which are
required for the growth and development of plant. These
nutrients are mostly iron, manganese, zinc, copper, boron,
molybdenum and chlorine. Out of these, chlorine deficiency
and toxicity is not generally observed in plants as this
micronutrient is supplied indirectly from various sources.
Though these micronutrients are required in trace/small
quantity, but their absence in the plant affect the plant.
Because, these nutrients are required to complete the life
cycle of the plant . The vegetative and reproductive growth
of the plant are also checked in absence of these nutrients.
These micronutrients are generally present in organic
sources of nutrients. These organic sources like FYM,
Compost, vermicompost etc
may contain less quantity of
these nutrients but presence of these help the plant in their
growth and development.
Soils supply these nutrients to the plants. When the
soil cannot supply therequired quantity of nutrient to the plant,
it starts showing deficieny symptom. On the contrary when
soil supplies more quantity of nutrient than the plant’s
requirement ,plant shows toxicity symptom . both deficiency
and toxicity are bad phenomenon for plant.
Plants show various symptom of deficiency in
absence of these but these symptoms sometimes
intermingle with symptom of plant diseases which confuse
the farmers. Therefore it is very essential to know the
symptom of deficiency and toxity of these nutrients so that
the farmers may take appropriate decision for management
of the problem. Here, the role of micronutrient in plant and
their deficiency /toxicity symptom in rice plant is described
in brief.
Iron
Role :
Chlorophyll development and function.
It plays a role in energy transfer within the plant.
It is a constituent of certain enzymes and proteins.
Iron functions in plant respiration, and plant metabolism.
It is involved in nitrogen fixation
Deficiency Symptoms
Iron
The most easily observed symptom of iron deficiency in
plants is extensive chlorosis in the leaves.
Generally the younger leaves are most affected, the most
mature leaves sometimes showing no chlorosis at all. This
is because of the relative immobility of iron in the plant. First
of all, interveinal chlorosis on surface of the leaf showing a
fine reticulate network of green setting off chlorotic areas.
Under severe deficiency conditions total chlorosis of the
younger or emerging leaves results.
Toxicity Symptoms
Tiny brown spots on lower leaves
starting from tip and spread
towards the leaf
base or whole
leaf coloured orange-yellow to
brown
Spots combine on leaf inter-veins
and leaves turn orange-brown and
die
Iron toxicity in rice
Leaves narrow but often remain green
In some varieties, leaf tips become orange-yellow and dry
up
Leaves appear purple-brown if Fe toxicity is severe
Stunted growth, extremely limited tillering
Coarse, sparse, damaged root system with a dark brown to
black coating on the root surface and many dead roots
Freshly uprooted rice hills often have poor root systems
with many black roots
Manganese
Role:
Important for normal functioning of many enzymes,
nitrogen metabolism and carbon dioxide assimilation. The
assimilation of carbon dioxide in photosynthesis.
It aids in the synthesis of chlorophyll and in nitrate
assimilation.
Manganese activates fat forming enzymes.
It functions in the formation of riboflavin, ascorbic acid, and
carotene.
It functions in electron transport during photosynthesis.
It is involved in the Hill Reaction where water is split during
photosynthesis.
Deficiency Symptoms
Chlorotic patches between veins are first noticed on
younger leaves. Stunted plants with normal tiller numbers
Toxicity Symptoms
Stunted Plants and limited
tillering .
Brown spots on the veins of
the leaf blade and the leaf
Manganese deficiency in rice
sheath in lower leaves..
Zinc
Role:
Production of Auxins, an essential growth hormone.
It activates enzymes in protein synthesis and is involved in
the regulation and consumption of sugars
It is necessary for starch formation and proper root
development.
Zinc influences the rate of seed and stalk maturation.
It is necessary for the formation of chlorophyll and
carbohydrates.
The presence of adequate amounts in the tissue enables
the plant to withstand lower air temperatures.
Deficiency Symptoms
The midrib of the younger leaves ,
especially the base , become chlorotic
Brown patches and
streakes in lower
leaves appear
Appearance of rusty-brown spots and
discoloration of older leaves beginning
Zinc deficiency symptoms
in rice
2-3 weeks after transplanting is noticed.
Under acute conditions, leaf margins of older leaves dry up.
New leaves are smaller in size.
Crop maturity is non-uniform and delayed.
Khaira disease of rice
Copper :
Role
It functions as a catalyst in photosynthesis and respiration.
It is a constituent of several enzyme systems involved in
building and converting amino acids to proteins.
Copper is important in carbohydrate and protein metabolism.
It is important to the formation of lignin in plant cell walls
which contributes to the structural strength of the cells, and
the plant.
Copper also affects the flavor, the storageability, and the
sugar content of fruits.
Deficiency Symptoms
Bluish- green leaves , which become
chlorotic near the tips.
Development of chlorosis downward
along both sides of the midrib,followed
by dark brown necrosis of the tips..
New leaves fail to unroll and maintain
a need like appearance of the entire
leaf.
Copper deficiency symptoms
in rice
Boron
Role
Maintains a balance between sugar and starch and
translocation of sugar and carbohydrates.
It is important in pollination and seed reproduction.
It is necessary for normal cell division, nitrogen metabolism,
and protein formation.
It is essential for proper cell wall formation.
It plays an important role in the proper function of cell
membranes and the transport of K to guard cells for the
proper control of internal water balance.
Deficiency Symptoms
Chlorosis at the tips of the older leaves , especially along
the margins , followed by the appearance of large, dark
brown elliptical spots in the affected parts, which
ultimately turn brown and dry up.
Molybdenum
Role:
It functions in converting nitrates (NO3 ) into amino acids
within the plant.
It is essential to the symbiotic nitrogen fixing bacteria in
legumes.
It is essential to the conversion of inorganic P into organic
forms in the plant.
Assessment
Choose the correct word/words :
i) Micronutrients are those which are required in large /
small / none of the above quantity
ii) Khaira disease of rice is a symptom of iron / zinc /
copper deficiency
iii) Chlorosis is a phenomena of loss of chlorophyll /
purple / burning of plant
iv) In case of Zinc, plants show more of deficiency /
toxicity symptom
v) Rice plants, generally do not show deficiency of
zinc / manganese / molybdenum