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Distributional pattern of water relations and net photosynthesis of Hammada scoparia (Pomel) Iljin in a desert environment.

Abstract：

:In the Central Negev, the arido-active Hammada scoparia (Chenopodiaceae) is mainly distributed in runnels and loessial plains of the wadis and exists with fewer and smaller individuals on slopes and tops of the neighboring hills. At the end of the dry season, water relations and chloride content of plants from these habitats and of artificially irrigated plants were determined and compared with plant shape and photosynthetic activity. The osmotic potentials and total water potentials of the plants differ characteristically with certain groups of stands. The simultaneously determined range of noon water potentials of the plants within a transect is as high as the annual amplitude of one plant individuum in the wadi (about 45 bars). Plants in the runnel of the wadi show, like the irrigated plants, the highest values of water potentials and their components but markedly lower chloride content than the irrigated ones. Total water and osmotic potentials of plants of the loessial wadi plains are extremely low. Their chloride content is not very high in contrast to that of plants of the hillslope and hilltop. Hill plants, although poorly developed and scarcely branched, have higher water and osmotic potentials than those of the plains.Net photosynthesis of a plant on a natural stand of the wadi plain is, in September, markedly depressed at noon but maximal at noon in an artificially irrigated plant. In contrast to irrigated and nonirrigated wadi plants, a plant of the hillslope shows, already in July, a midday depression of photosynthesis. Whether the relatively low water potentials of the big plants of the loessial plains are the results of a rapid biomass production in the rainy season which might have caused a very strong exhaustion of the soil water reserves for the late summer is discussed. Hill plants do not grow so well and obviously decrease their water exchange even in summer.

journal_name

Oecologia

journal_title

Oecologia

authors

Kappen L,Lange OL,Schulze ED,Evenari M,Buschbom U

doi

10.1007/BF00345961

subject

Has Abstract

pub_date

1976-12-01 00:00:00

pages

323-334

issue

eissn

0029-8549

issn

1432-1939

pii

10.1007/BF00345961

journal_volume

pub_type

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Distributional pattern of water relations and net photosynthesis of Hammada scoparia (Pomel) Iljin in a desert environment.