The Regulation Of ABA,Ca～(2+) On Proline Accumulation In Eremochloa Ophiuroides Under Water Stress

Proline, as an osmolyte , plays a crucial role in plants during adaption to various types of environmental stresses. Eremochloa ophiuroides is a main warm-seasonal turf-forming turfgrass due to its strong drought resistance. The paper mainly studied the probably pathway of proline accumulation in five-leaf-stage seedlings of Eremochloa ophiuroides under water stress (20% PEG6000 treatment and natural water loss), explored the effect of exogenous ABA and CaCl2 on proline accumulation , aiming to lay a foundation to raise the drought tolerance of turgrass.Our results were showed as follows:1. After the treatment of 20% PEG6000 on the roots of Eremochloa ophiuroides seedlings , the level of proline in leaves was increased significantly to the highest in 16 hours ; Leaves ranked the first in the ability of proline accumulation , shoots second and the roots ranked 3.2. A 1-pryrroline-5-carboxylate synthestase (P5CS) and Ornithine- 8 -aminotransferase (OAT) are the key enzymes of proline biosynthesis. The activity of P5CS was decreased continuously under water stress for 24 hours, whereas the activity of OAT was increased constantly. It is suggested that the proline accumulation of Eremochloa ophiuroides is mainly regulated by OAT activity , given the close relationships between the proline content and OAT activity (The correlation coefficient is 0.96).3. The proline content was increased rapidly after spraying ABA(50mol/L) on theleaves of Eremochloa ophiuroides .Compared with the cotrol, the proline content was markedly higher, about 1.9 times higher than that of the latter after 7 days when ABA was sprayed. Meanwhile , the activity of P5CS was increased but the OAT activity was decreased. It is indicated that the mechanism of P5CS and OAT responsive to ABA might be different.4. Treated with ABA, the activity of SOD was slightly lower than that of the control for 3 days. Afterward , the activity of SOD was increased higher than that of the latter. Isoenzyme analysis showed that ABA inhibited SOD activity after spraying ABA (in 12h), the gray level of SOD spectrum band was lower than that of the control.5. After soaking the roots of Eremochloa ophiuroides in 2mmol/L CaCh solution, proline content was slightly increased; but the proline content in leaves sprayed with CaCh was markedly higher than that of the control. Both P5CS and OAT activity were increased, MDA content was decreased, SOD activity was increased in 5 days aftertreatment.