- Control of microclimate by modifying either leaf temperature or humidity. Earlier we studied how plants can control loss of water through formation of boundary layers which keep a layer of moisture close to the stomata to decrease tranispiration rates. However they can also mechanically produce the reverse effect.
Insects are very sensitive to humidity- can't tolerate dry/wet fluctuations
When we measure photosynthetic rates, we will see the rapid changes in relative humidity of air passing over the leaf.. in some cases we saw as much as 20% differential with opening of stomata...
- Make it difficult to maneuver on the leaf
Make it very smooth and slippery ( holly) or very rough to manuveur with trichomes- these are hairs on the leaf often with barbs that may in some cases contain irritants or poisons. ie. impacts as subtle as squash inducing a rash or worse from compounds released by the trichomes... or much worse.. poison ivy/oak.
- Gummosis-sticky stuff that jams up a probisus and sclerids- internal stony sclerenchyma projections which can wear down chewing molars... as in pears...
2. Nutritional keep moisture below 60% is espcially with fungi who need moisture - or keep Nitrogen / amino acid levels very low which makes it difficult for insects or larger animals to survive on a high carbohydrate & low protein diet.
One good thought is, with global warming plants will grow faster but contain less Nitrogenous products relative to carbohydrates... will this cut down on fungal infections?
Go on to the next page on biosythesis of secondary compounds or return to main defense page.....