Guy’s news: Plants; not so dumb & passive

Much of horticulture is about managing the urge of plants to reproduce. Humans need and crave the more digestible, nutrient-dense food found in the reproductive parts of crops; that is the flowers, fruits, seeds, bulbs and tubers. As growers we devote ourselves to manipulating plants to maximise the yield and quality of those tender and tasty reproductive organs, which is a tricky balance to strike. If only we could sell you grass for your supper; alas the easy to grow, non-reproductive parts of plants are largely indigestible to humans.

Much of horticulture is about managing the urge of plants to reproduce. Humans need and crave the more digestible, nutrient-dense food found in the reproductive parts of crops; that is the flowers, fruits, seeds, bulbs and tubers. As growers we devote ourselves to manipulating plants to maximise the yield and quality of those tender and tasty reproductive organs, which is a tricky balance to strike. If only we could sell you grass for your supper; alas the easy to grow, non-reproductive parts of plants are largely indigestible to humans.

Plants in their wild state have survived the challenges of pestilence, drought, flood, ice ages and now Homo sapiens by mastering a long-term strategy of balancing growth and dominance against risk. Getting bigger to increase their reproductive capacity must be balanced against the risk of not making it to maturity. At a cellular level the strategy all boils down to whether a cell in the apical meristem (growing point) differentiates into leaf or flower (above ground) and root or starch-saving tuber (below). If things are looking good a plant will
typically extend its vegetative life, assuming the chance for greater fecundity will come later; if things are getting tough (drought, lack of nutrients or light etc) it will switch to sexual mode early so at least some genes are preserved.

Such were my musings as I observed our early runner beans which have grown and grown but failed to produce a crop. The generally-held wisdom is to build a strong plant, then stress it with water deprivation to make it flower, then give it everything it needs so it feels confident and fills every pod. As our plants reach for the polytunnel roof and the soil is covered with aborted flowers and just a few crates of beans to show for it, it’s plain we haven’t grasped the subtleties.

There is a tendency to regard plants as dumb and passive, yet their interaction with the world goes far beyond the basic tropisms we learnt at school. They can sense, even “hear” pest attack and respond with defence chemicals, much as our own immune system works. They may not moo, baa or rush around, but the apparent passivity of plants hides subtleties and complex responses which have served them well. It remains to be seen how well they will survive us.

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