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tassel signals

daemon at net.bio.net daemon at net.bio.net
Fri May 8 08:41:19 EST 1998

Hello Peter,

We are also interested in the control of flowering in maize and the
interactions between tassel and ear, but what exactly do you call 'ear
initiation'? Following is a short piece of text from a paper I published in
the 'Flowering Newsletter' last year. Basically, we observed that, in
maize, the male and female floral transitions are separated in time, and
that is why anthesis and silking occur at different times. However, there
must be some kind of mutual control, but to my knowledge its exact nature
is not known. For more info on this, you can read the following paper:
Lejeune, P. and Bernier, G. Effect of environment on the early steps of ear
initiation in maize (Zea mays L.). Plant, Cell & Env. 19: 217-224, 1996.


In practice, it is possible to estimate the moment of tassel initiation at
the apex by considering that it occurs when the number of leaves visible
with the plant held at eye level is about 45-50% of the total number of
leaves (5). The situation is less simple for the female inflorescence which
is produced on an lateral branch several nodes below the tassel. All the
axillary buds have the potential to form an inflorescence but, in general,
only the topmost one or two will bear grains. We observed that axillary
meristems are initiated during the vegetative phase at the same rate as
leaf primordia, but with a delay of 5-7 plastochrons, depending on the
genotype. This lag corresponds to the number of nodes between the apical
tassel and the topmost ear. At tassel initiation, maize plants
simultaneously stop to initiate axillary meristems, with the consequence
that the topmost ear-shoot is initiated on the same day as the tassel (4).
At this point, the lower axillary buds are more advanced than the upper
ones but this situation rapidly reverses so that the first flowers are
always initiated on the topmost bud. Since several husks (modified leaves
enclosing the ear) are produced before the inflorescence, it ensues that
the female floral initiation follows, but is temporally separated from,
tassel initiation. However, the fact that the tassel and the topmost
axillary meristem are initiated simultaneously indicates that these two
events are probably triggered by the same endogenous factors, or,
alternatively, that there is some kind of mutual control.

A 12:38 7/05/98 -0500, vous avez =E9crit :
>Ed...I liked your directions to the flavonoid person. But, I have another
>question. What is known about tassel signals that affect ear initiation. We
>all know that most tassels precede ear initiation. At times, there are
>lines that have a big gap. I wondered if anyone has studied the GA or other
>compounds that affect this process. Let me know if someone there has a clue
>on this. thanks.	Peter


Universite de LIEGE
Dept. Biologie Vegetale
Service de Physiologie
Sart Tilman B22

Tel: (32) 4 366 38 36
=46ax : (32) 4 366 38 31
Email : Pierre.Lejeune at ulg.ac.be

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