Beneficial effects of direct foliar water uptake on shoot water potential of five chasmophytes

Abstract

Five chasmophytic species growing as wall-fissure plants on vertical retaining walls of a castle in the town of Patras, Greece, were examined for their ability to benefit from direct absorption of foliar surface water. Epifluore scence microscopy and application of an apoplastic tracer of water movement indicated that sprayed water on leaf surfaces penetrated into the mesophyll of all species, and in some cases was also detected within conducting tissues of the leaf. Water potential (Ψw) of sprayed detached shoots was improved compared with unsprayed controls when they were slowly losing water under laboratory conditions. The beneficial effect of leaf water absorption on Ψw was found either on leaves that were originally fully turgid or on leaves that had undergone a considerable water content reduction. Sprayed leaves maintained their Ψw above turgor loss point for a time period of 10-90 min depending on species and degree of water deficiency. The relevance of the results to the importance of dew uptake from chasmophytes growing under water shortage in wall fissures in inhabited areas is discussed.Key words: chasmophytes, leaf water absorption, wall vegetation, drought resistance.

Vertical patterns and duration of surface wetness in an old-growth tropical montane forest, Indonesia

“…On the other hand, there is substantial evidence that leaves expand more rapidly under high air humidities, and leaf conductance typically is higher under low saturation deficits which may enhance photosynthetic carbon gain (e.g. Gouvra and Grammatikopoulos, 2003;Hanba et al, 2004). Whether high levels of air humidity are significantly affecting tree growth in tropical montane forests and whether positive or negative effects on growth are prevailing, may largely depend on the duration of periods with saturation deficits close to zero.…”

Diurnal and seasonal trends of water relations in five co-occurring chasmophytic species

“…However, absolute values of transpiration rate differed between species as well as seasonally within species. The differences can be attributed to the seasonal change of evapotranspiration demand (which is strongly affected by air temperature and RH) (Gouvra and Grammatikopoulos, 2003) as well as to the differential use of water reserves by the species. High transpiration rates during spring and summer in H. albus, R. picroides and P. judaica suggest a rather ''water spending'' strategy, as adaptation to water shortage during this period.…”

“…In another study, the possible contribution of mycorrhizal hyphae to water uptake from fissures is discussed (EgertonWarburton et al, 2003). To our knowledge, water relations of wall-fissure plants have only once been studied in the past (Aschan and Lo¨sch, 1994), while recently foliar water uptake was reported (Gouvra and Grammatikopoulos, 2003). Aschan and Lo¨sch (1994) examined two species during fall and early winter, a period when foliage often experiences adverse conditions in northwestern Germany.…”

Living on the edge: Ecology of an incipient Betula-fungal community growing on brick walls

“…Very few studies have taken ecological or ecophysiological measurements of plants or substrate on walls. Those measurements were generally limited to water relations and foliar water uptake (Aschan and Lösch 1994; Gouvra and Grammatikopoulos 2003).…”