Long-term effects of drought on wild and cultivated plants in the Negev desert

✍ Scribed by E. -D. Schulze; O. L. Lange; M. Evenari; L. Kappen; U. Buschbom

• Publisher: Springer-Verlag
• Year: 1980
• Tongue: English
• Weight: 623 KB
• Volume: 45
• Category: Article
• ISSN: 0029-8549
• DOI: 10.1007/bf00346701

✦ Synopsis

The seasonal change in diurnal patterns of net photosynthesis and daily carbon gain is studied in relation to the plant water status of the irrigated and non-irrigated naturally growing desert species Hammada scoparia, Zygophyllum dumosum, Artemisia herba-alba and Reaumuria negevensis. Comparison is made to cultivated Prunus armeniaca. Under non-irrigated natural conditions Hammada scoparia, a C plant, showed one-peaked flat diurnal courses of CO uptake which changed into a pattern of a high morning peak of CO uptake or slightly two-speaked curves in the late dry season. In contrast, the C species Zygophyllum dumosum, Artemisia herba-alba and Prunus armeniaca changed from one-peaked to distinct two-peaked patterns. At the end of the dry season, non-irrigated plants showed respiration only. Reaumuria negevensis had one-peaked curves with a low level of CO uptake.There is no general relation between day-time CO gain and pre-dawn water potential for the investigated species. In order to characterize the effect of soil drought, the CO gain during day-time of non-irrigated plants is expressed as a percentage of the CO gain of the irrigated counterparts. After an initial period of minimal drought effect, the relative day-time CO gain decreases almost linearly with cumulative water stress as determined by the daily addition of pre-dawn water potentials for the non-irrigated plants since the last rainfall. The slope of decrease differs from species to species. The relation of daily CO gain to maximal net photosynthesis is discussed. Initially, at a good plant water status, the daily CO gain does not decrease in proportion to the maximal photosynthetic rates as a result of stomatal control at high photosynthetic activity. At increasing water stress the daily CO gain decreases more than proportionally to the decrease of the maximal rates.