Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: 9/1/2007
Publication Date: 11/8/2007
Citation: Wilson, C. 2007. Effect of Jasmonic Acid on Growth and Ion Relations of Oryza sativa L. Grown under Salinity Stress. American Society of Agronomy Meetings. Paper No. 63-14 Interpretive Summary: In the field, plants are challenged by multiple stresses. One of these stresses, salt stress, is a major factor in limiting crop reproductivity. To survive these unfavorable conditions, plants employ adaptive tolerance mechanisms. These mechanisms are often triggered by signaling mechanisms including plant hormones. Recent studies in our laboratory on gene expression in salt-tolerant barley revealed that salt stress regulates a plant hormone synthesis pathway, jasmonic acid (JA), and genes which respond to (JA). It is thought that JA is involved in the adaptation of barley to salt stress. In this work, we examined the hypothesis that JA also plays a role in salinity adaptation in salt sensitive crops, such as rice. Our results indicate that in contrast to salt-tolerant barley, JA treatment reduced growth as measured by shoot and root dry weight of shoot and root length. We further examined the effect of JA on mechanisms important for plant growth such as photosynthesis. Again, consistent with our finding on growth parameter, JA pretreatment, did not alleviated photosynthetic inhibition caused by salinity stress. It is thought that growth reduction due to salinity is related to uptake of salts, especially sodium. We examined JA treatment on salt uptake. Rather than reduce ion uptake as in barley, JA dramatically increased salt uptake. Further work is underway to investigate the differential response of salt-tolerant and salt-sensitive plants to JA.
Technical Abstract: Rice (Oryza sativa L.) is considered salt sensitive compared to other cereals. Recent transcriptome studies on salinity stress response in barley revealed indicates that exogenous application of jasmonic acid (JA) can ameliorate growth reductions brought about by salinity stress. It is hypothesized that JA plays a role in adaptation of some plants to salinity stress. In this study, we investigated whether or not application of exogenous JA to salt-sensitive rice (indica cultivar IR29) can also ameliorate salinity stress. All three treatment employed, salinity, JA pretreatment, and JA-pretreatment salinity-stress reduced growth as measured by shoot and root dry weight of shoot and root length. JA pretreatment prior to salinity stress did not appear to ameliorate growth reductions due to salinity stress. Gas-exchange responses were also compared after salinity stress, JA pretreatment, and JA pretreatment followed by salinity stress. Consistent with our finding on growth parameter, pretreatment with JA did not alleviated photosynthetic inhibition caused by salinity stress. Also, the JA-pretreated salt stressed plants accumulated dramatically higher levels of Na+ in the shoot tissue compared to untreated salt-stressed plants. Ions such as Ca2+ and Cl- also increased while other ion such as Mg2+ and K+ decreased. We detected no change in S levels. Analysis of selectivity constants for K:Na, Ca:Na, K:Mg, and Ca:Mg indicated that ion homeostasis was greatly affected by JA pretreatment. We concluded that JA pretreatment in rice does not ameliorate salinity stress, possible due to increased accumulation of toxic ions and changes in ion homeostasis.