If you stand on the third-floor balcony of F7B facing towards Wally’s Walk, in t

Question

If you stand on the third-floor balcony of F7B facing towards Wally’s Walk, in the middle of September, you can see eight Plane trees (Platanus x acerifolia). Seven of them will have substantial growth of fresh new leaves over the whole tree. The eighth tree, which is located at the eastern end of the row of trees, will have only a few leaves that have recently emerged. If you look at them again a month later, all the trees look the same with full foliage. This growth pattern has been observed every September for at least the last 10 years. a) Provide two different brief explanations which might explain this phenomenon. b) Choose one of your explanations provided in part A, and explain how you would design an experiment to determine if your hypothesis was correct.

Explanation / Answer

(a) This might be caused by the fungus Apiognomonia veneta. We have had many reports in the past of American sycamores (Platanus occidentalis) and London plane trees (a cross between American sycamore and Oriental plane tree with the scientific name Platanus x acerifolia) that show significant shoot blight and defoliation. The fungus overwinters in cankers from previous infections, and produces spores in the spring that are dispersed by rainfall to young developing shoots.

The second reason can be season that is drought and heat stress. The symptoms you describe appeared very suddenly, when the weather turned hot and dry in the second half of July. The overabundant rains of June and early July created a situation that kept soil saturated, which probably caused a portion of the trees’ fine feeder roots to rot and die. Fine feeder roots are responsible for absorbing water and nutrients from the soil, and represent the largest mass of a tree’s root system.

(b) We can choose the seasonal experiment and give good amount of water to trees, as will be given by rains of june and early july and then put them under hot and dry season. We should be able to see the results.

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