Eco-physiological studies on desert plants

Summary The O₂ uptake and RQ of germinating negatively photoblastic Zygophyllum coccineum seeds were studied during the first fourty hours after soaking in water under dark or light conditions. Five phases could be distinguished in the course of O₂ uptake in water in dark. The respiration course in light did not differ from that in dark till the 12th hour after soaking, then it deviated showing a low level, The RQ values in dark and light are nearly identical; both had sharp decline between the 8th and the 16th hour after soaking. Light, by blocking germination, affected the O₂ uptake.Moisture stress simulated by mannitol solutions caused a decrease in the O₂ uptake of seeds and seedlings. Na₂SO₄ caused a reduction and a lag in the time of maximum O₂ uptake. NaCl showed a particular effect on respiration of germinating seeds causing earlier rise and decrease in O₂ uptake than in water. NaCl was effective in rising the O₂ uptake of seedlings specially those supplied with glucose. Its effect was not pronounced on starved seedlings. O₂ uptake of seedlings germinated in NaCl was considerably high when compared with that of seeds germinating in the same medium 40 hours after soaking.The decreasing effect of moisture stress caused by mannitol on O₂ uptake was reversed by diluting the medium or replacing it with water. Values of O₂ uptake on number of seedlings basis are different from those calculated on fresh weight basis due to the difference in water content of seedlings germinated under various conditions.