Monteith's View On the Roll of Dew in Nature.

Monteith  pioneered the quantitative dew research in the late fiftieth-early sixties.The purpose here is to reexamine the ecological importance of dew in light of his research. This reevaluation is of particular interest under the controversial perspective that dew is insufficient as a source of water for plants but is sufficient to promote the spread of plant diseases. In his first paper (1957) and later in Israel (1960 in Hebrew ) he measured maximum  0.05-0.06 mm hr^-1 . This led him to claim (1963 ) that " every poet who has sung the beauties of Nature has added his tribute to the sparkling dew drops…and ecological investigations of dew have strayed into description which belong to poetry  whereas for purely physical reason dew is unlikely to support the water budget of  plants because the ratio of potential condensation to potential evaporation is roughly 1:7 in humid climate and 1:14 in arid climate" . On these grounds it can be argued that the contribution of dew to the overall water regime is negligible. Thus, From the biological viewpoint, the usefulness of dew is doubtful, as dew may stimulate the growth of fungi harmful to plants. (Encyclopedya Britannica 2013). Amazingly nothing is mentioned about the favor of dew to the plant water regime. Contrary to expectations, we detected separate, early peaks of photosynthesis  and late peaks of transpiration, leading to an average ratio of about 2:1 units of water use efficiency (WUE) for dew-affected versus no-dew conditions. The impressive performance of the dew-affected WUE was explained by a synergy between (1) low transpiration during dew-affected morning hours and (2) night respiration increased CO₂ gradient toward the canopy. This synergy resulted in intensive carbonintake at a low water cost and explained the ecological importance of dew.