Gamal Fahmy

Abstract: Cistanche phelypaea (L.) Cout. (Orobancaceae) was found parasitising the roots of the succulent shrublets Arthrocnemum
macrostachyum (Moric.) K.Koch (Chenopodiaceae) in a coastal salt marsh in Qatar. Measurements were conducted to identify soil
properties, host, and noninfected plants by soil excavations to expose the haustoria of the parasite attached to the host roots. The water
potential, osmotic potential, pressure potential, and chemical analyses were determined in parasite, host, and noninfected plants. Crown
diameter and dry mass of the host plants were smaller than in the noninfected plants. A gradient of water potential existed between the
host root and the underground tuberous body of the parasite. Potassium was the major cation found in the parasite, while sodium was
dominant in the host and noninfected plants. The nitrogen, soluble sugars, total amino acids, and starch contents of the parasite were
higher than those of the host and noninfected plants. The high ratio of K+ to Ca2+ in the parasite indicates that it is phloem-feeding. The
high nutrient element contents and metabolic products in the parasite are possibly related to the creation of osmotic and water potential
gradients between the host and C. phelypaea.