Selfwatering Plants?

Rain brewing over the Opera House, taken from the Sydney Harbour Bridge while on the Seven Bridges Walk today. Yes it did rain, and should I blame the plants in the botanic gardens behind this music hall?

In short, and oversimplifying things awfully, some plants have the ability to water themselves!Jonathan Garner, landscape gardener and councillor of the Australia Insitute of Horticulture, sent around this fascinating story about plants, bacteria and rainfall.

Better let Jonathan tell the story.... He says: "I was listening to an amazing bbc documentary about bio precipitation and the role bacteria’s play in weather. The practice of cloud seeding with certain elements has been popular for quite some time. A fella by the name of David Sands from Montana university proposed the concept of cloud seeding with bacteria in the late 1980’s. Since then ski resorts have been utilising bacteria to initiate snowfalls.

"The fascinating thing is that this bacteria Pseudomonas syringae and its many pathovars finds nourishment and as such undergoes accelerated cell division (procreation) on the leaves of plants. Why? and How?

"Well. Pseudomonas is extremely effective at making water freeeeeeeze (ice nucleator). It has a protein that makes water molecules stick together at warmer temperatures. In fresh water, without a catalyst to make water molecules stop moving around so quickly to begin the process of becoming a solid, the temperature required is -40c ish. The freaky thing is Pseudomonas initiates ice nucleisation at temps of 0c - -5c.

"Why does it breed on leaf lamina? I’m glad you asked. Pseudomonas initiates frost at warmer temperatures. When ice forms on foliage, the jagged sharp ice crystals penetrate the leaf lamina and as such provide easy access for pseudomonas to dine on the plant without having to personally invade the plants outer defences. It also side steps the plants natural reaction of developing phytotoxins or defense mechanisms when attacked by a parasite. The downside is that pseudomonas is responsible for types of cankers and other plant diseases. The upside is that pseudomonas syringae is being trialled for its effectiveness at controlling fungal decay during storage of fruits and vegetables.

"Back to its ability to initiate freezing process. It’s common knowledge that in order for rain to fall, the water molecules in the clouds need to cling together (freeze) so that gravity can bring it down here as rain. Well. The funky thing is that during spring and summer when transpiration is in full swing, the Pseudomonas enter the atmosphere via air movement & as hitchhikers within water vapour during transpiration. So the huge populations of pseudomonas that have bred on the foliage & fed on plant material by making water freeze on the foliage to access an easy meal, float up into the atmosphere and initiate precipitation for the plants to take advantage of.

"The interesting thing is that science has discovered that certain varieties of crop have the knack of hosting massive populations of Pseudomonas compared to other varieties within the same species. Certain cultivars of barley for instance. With this knowledge in hand, plant breeders will be able to cross these strains with other strains to create cereal crops that will allow more of these cloud seeding critters into the atmosphere and as such improve the necessary initiation of ice crystals at warmer temperatures bringing the opportunity of a natural process of cloud seeding.

"To take things another step further. It isn’t often that nature allows a forest full of diverse plant life to die from drought. It would seem that we are getting closer to having the factual proof that areas with high quantity of vegetation actually create the rain required for the cycle to continue."

Thanks Jonathan!