Eldan Goldenberg's lab notebook

Jennifer Nemhauser - Quite contrary models of how gardens grow

Jennifer Nemhauser gave the first talk, about the work in her lab on the small molecule hormones that influence plant growth.

Nemhauser explained one example in detail; I don't know if this is the only thing they experiment on, or just one picked out for the sake of a short talk. The behaviour was that arabidopsis seedlings express different growth patterns depending on whether they are growing in direct light or shade. The shade-grown plant will tend to grow tall fast, in preference over increasing its leaf area, while a clone of the same plant grown in sun will become more bushy. The evolutionary advantage of this is simply enough explained (as by Trewavas) in terms of plants expressing the growth pattern that optimally collects sunlight—grow lots of leaves if already in the sun, or grow tall if in the shade because that increases the chances of reaching a patch of sunlight—and it's something I've been able to observe quite clearly with my tomato plants.

Nemhauser's research looks at the chemical signals that mediate this behaviour; specifically that auxins promote the tall, thin patter and brassinosteroids promote the short, bushy pattern. However, as with much in biology, the effects are neither linear nor decouplable - suppress one chemical altogether and the effect of the other is also lost. Her lab has gone into some detail elucidating the pathways through which these molecules interact. I must confess to not having been able to follow the biochemical detail in such a quick overview, but the overall message I got was that this is a perfect example of a complex system: no part of it really makes sense without the other inputs and outputs considered.