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 broccoli
4.4 PHYSIOLOGICAL DISORDERS
Broccoli crops show various non-parasitic disorders which cause tissues to die off. In some
cases, these deviations have been shown to depend mainly on heritable characters; whereas in
other cases external factors had a least marked effect.

Blindness
Plants do not form heads, but produce many shoots at ground level. This may be caused by
insects or damage to the growing point early in the plants life.

Leafy Heads
Small leaves develop and protrude through the head during high temperatures, drastic
fluctuations in day and night temperatures or improper nitrogen balance.

Broccoli buttoning
Buttoning is the premature formation of a head 2.5 to 10 cm in diameter. Buttoning can occur
anytime between seeding and almost mature plant, but usually occurs shortly after transplanting
into the field. Generally foliar growth slows after buttoning resulting in too few nutrients to nourish
the curd to marketable size. Losses are usually most severe in the early planted crop during
cold, wet seasons, when vegetative growth is affected by:
1. too much hardening of greenhouse plants
2. too little hardening of greenhouse plants
3. low soil nitrogen
4. low soil moisture
5. continued cold weather (4 to 10 0
C for day or more)
6. Other – disease, insects, micronutrient deficiency, etc.
Some cultivars, particularly early ones, are more susceptible to buttoning than others.

Lack of heads in broccoli
During periods of extremely warm weather (days over 30 0
C and nights of 25 0
C) broccoli can
remain vegetative (does not head) since they do not receive enough cold for head formation.
This can cause a problem in scheduling the marketing of even volumes of crop.

Hollow stem in broccoli
Symptoms are internal only. This condition starts with gaps that develop in the tissues, and
gradually they enlarge to create a hollow stem, sometimes from the bottom of the stalk into the
head. Ordinarily, there is no discolouration of the surface of these openings at harvest, but both
discolouration and tissue breakdown may develop soon after harvest. Avoid excessive nitrogen
 after head initiation. Dense plantings will maintain even growth rates and decrease the
occurrence of hollow stem.



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