WEATHER

NUTRITION

SOIL MOISTURE

PLANT PROTECTION CHEMICALS

HORMONES

CULTURAL PRACTICES

MANAGEMENT PRACTICES

TEMPERATURE

DAY LENGTH

LIGHT

WIND

RAINFALL

Most of the crops require moderate temperatures for

flowering and pollination such that good seeds are

formed.

Too high temperatures cause desiccation of pollen

resulting in poor seed set.

If hot dry weather conditions prevail during flowering

many crops such as vegetables, legumes and fruit trees

fail to set seeds effectively and produce many seedless

fruits .

Vegetables, legumes, fruit crops require cool conditions

to flower and pollinate normally.

Though oil crops can withstand hot periods during

flowering, very high temperatures result in premature

flowering, and production of poor quality seeds.

Very cold temperatures may also damage seed quality

especially in the early phases of seed maturation

Very low temperature (0⁰C and below)damages

ripening of corn seed. (Rossman, 1949).

Very high temperature increases the rate of respiration,

decreases grain weight.

In Lettuce koller (1962) noted that when the seeds

matured at high temperatures, germination was less at

26⁰C in the dark than the corresponding low

temperature matured seed.

Temperature differences during ripening also altered

the dormancy patterns of wheat (Van Dobben, 1947;

Kramer, Pest, Witten, 1952).

In Mungbean, Dharmalingam (1982) showed the late

summer sowing in Tamil Nadu resulted in the

production of high % of hard seeds.

Excessive rainfall leads to higher incidence of pests and

diseases and makes seed useless.

It may result in delayed maturity and pre germination

of seeds in many standing crops.

Heavy rainfall at harvest time may cause heavy seed

losses .

CROP CLIMATIC FACTOR CHANGES IN SEED CHARACTER

Sorghum Rainfall or high humidity at maturation

Blackening of seed due to black mould

Pulses Rainfall at maturation

Off coloured seed

Peas High humidity at maturity

Mottled seed

Groundnut Rainfall at harvest Insitu germination

Brinjal High temperature at flowering

Pseudo styled flowers

Tomato Rainfall at harvest Insitu germination

Bhendi Rainfall at maturity Off coloured seed

POOR SEED SET

FLOWER DROPPING

REDUCED SEED SIZE

REDUCED SEED YIELD

Ripening of the seed on the Parent plant.

Chinapodium amaranticolor and ononis sicula seeds

maturing during long days showed coat-imposed

dormancy due to thickening of the seed coat ( Lona,

1947, Austin, 1972).

Ample Daylength is required for better seed

development and maturation.

Strong winds at or near, harvest time causes heavy seed

losses .

The structural and textural status of the soil, its fertility

level, pH, microbial environment.

In the nutrition of seed crops, nitrogen, phosphorus,

potassium and several other elements play an important

role for proper development of seed.

It is advisable to know and identify the nutritional

requirements of seed crops and apply adequate

fertilizers.

Adequate fertilization results in good seed development

and maturation.

Adequate supply of nitrogen is very important for a

good healthy seed development.

Excess quantity of nitrogen prolong the growing period

and delays the seed maturity.

Time of application of nitrogen is important.

The second application often leads to an increase in

quality seed.

In some crops dressings at flowering tends to delay in

seed ripening.

Severe nitrogen deficiency in carrot, lettuce, and

pepper resulted in poor seed development.

High dose of nitrogen reduces development in seed due

to accumulation of germination inhibitors

A good supply of phosphorus helps in good

seed development.

Phosphorus deficiency retards overall growth

and development.

It should be applied in the soil before sowing

In certain crops, a side dressing of phosphorus

is also applied at the time of flowering.

The P reserves in the seed in the form of

phytic acid and acts as a antioxidant.

Deficiency of P causes watercress seeds.

Potassium plays an important role in flowering

and seed development.

Helps in synthesis of proteins and fat in oil crops.

Severe deficiency of potassium in pepper resulted

in a higher percentage of abnormal seed

production.

Deficiencies of other essential major and minor

elements may also affect the quality of seeds.

For good-quality seed, a relatively dry climate

during the ripening phase is preferred.

Even for a wetland crop like rice, a dry climate

during grain ripening phase produces seeds of

good quality

Adequate soil moisture is essential for good

seed development.

Soil with high moisture due to high irrigation

or high rainfall may lead to seeds of low

nitrogen and protein content in case of wheat.

Drought during flowering might interfere with

fertilization, thus seed number is reduced.

Weight and size of seed which are usually correlated

with viability, are reduced by drought during seed

development and maturation.

Extreme water deficit stimulates premature desiccation,

and affect the quality of seed.

As such seeds badly affected by pre-harvest rains

should not be stored for planting purposes.

Association of water deficit and thermal stress during soybean

seed filling (França Neto and Krzyzanowski)

water deficit

Herbicides and pesticides applied to the soil or to the

growing crop may affect the development of seed and

influence its quality.

If the concerned herbicide or pesticide is not easily

biodegradable.

Increase in the protein content of wheat with sub

herbicidal doses of Simazine (Ries, Schweizer, and

Chmiel, 1968).

Ramamoorthy (1990) systemically studied the effect of

the herbicides FLuchloralin, Pendimethalin, on

viability of seeds.

AUXINS

GIBBERLINS

CYTOKININS

ABSCISIC ACID

Auxins (cell elongation)

Gibberellins (cell elongation + cell division -translated into growth)

Cytokinins (cell division + inhibits senescence)

Abscisic acid (abscission of leaves and fruits + dormancy induction of buds and seeds)

Ethylene (promotes senescence, epinasty, and fruit ripening)

Seeds selection

Isolation

Time of planting

Roguing

Supplementary pollination

WEED CONTROL

DISEASE AND INSECT CONTROL