Subject: Re: Roses and Rumours
From: Tony Travis <[email-masked]>
Date: 2 May 1994 16:37:45 +0100
Newsgroups: bionet.plants

Julius L Heinis said:
> 
> [...]
>     (I don't think you meant absisic acid - this would make
> the leaves drop and age flowers ver fast).   JULIUS

Oh yes I did!

ABA is synthesised under water stress, and has different roles in the
control of plant growth - leaf abscission is only one of them and the
interactions of ABA with other hormones are also important.  See recent
work by Bill Davies at Lancaster (UK) on the importance of ABA
synthesis by the mesophyll on stomatal behaviour in Commelina communis.

ABA closes the stomata, and so does aspirin - cut flowers last longer
if they don't wilt: the basic problem is that _most_ people get air
into the vascular system when they cut the stems and the embolisms this
produces block the xylem.  Then, the plants just wilt and die. 

The 'confusion' of ASA and ABA was offered informally in the bar at a
conference to explain why people were working on the use of aspirin as
a potential anti-transpirant.  The occurence of salicyic acid in willow
may be important though ...

Hammering the ends of the stems is an old growers trick (!).  It's a
warning to the rest of the plant to cooperate - or else ... and it
opens up the ends of the vascular tissue.  Plants are well adapted to
limit the damage caused by air embolisms and so preserve the continuity
of the water column under tension in the xylem.

	Tony.
-- 
Dr. A.J.Travis,                       |  JANET: <[email-masked]>
Rowett Research Institute,            |  other: <[email-masked]>
Greenburn Road, Bucksburn,            |  phone: +44 (0)224 712751
Aberdeen, AB2 9SB. UK.                |    fax: +44 (0)224 715349