Why will be the ph of succulent leaves acidic during night?
Answers
Using determinations of overnight changes in tissue titratable acidity and of tissue stable carbon isotope ratios, 10 species of terrestrial succulents were investigated in situ in southeastern Jamaica for the presence of Crassulacean acid metabolism (CAM). Eight of the 10 species exhibited CAM (sensu lato), confirming past reports of CAM in Clusia flava (Clusiaceae), Bryophyllum pinnatum (Crassulaceae), Euphorbia tirucalli (Euphorbiaceae), and Pedilanthus tithymaloides (Euphorbiaceae) and extending the number of species with CAM in two genera previously known to contain CAM species (Agave sobolifera [Agavaceae] and Sansevieria metallica [Liliaceae]). Stems of both E. tirucalli and P. tithymaloides exhibited CAM while the leaves of both species were intermediate with regard to photosynthetic pathway. The lack of CAM acid fluctuations in Talinum paniculatum (Portulacaceae) was surprising given past findings with all other species investigated in this genus. Shoots of Pilea microphylla (Urticaceae) were C₃ yet were remarkable in their extremely high pH. Both species require further investigation. Nocturnal acid accumulations indicative of CAM were found in Tripogandra multiflora and Callisia fragrans, both members of the Commelinaceae. This represents the first report of CAM (probably "CAM-cycling") in this family.
Explanation:
Crassulacean acid metabolism (CAM) was investigated in leaves and stems of the succulent C4 dicot Portulaca oleracea L. Diurnal acid fluctuations, CO2 gas exchange, and leaf resistance were monitored under various photoperiod and watering regimes. No CAM activity was seen in well watered plants grown under 16-hour days. Under 8-hour days, however, well watered plants showed a CAM-like pattern of acid fluctuation with amplitudes of 102 and 90 microequivalents per gram fresh weight for leaves and stems, respectively. Similar patterns were also observed