Use of positron-emitting tracer imaging system for measuring the effect of salinity on temporal and spatial distribution of C tracer and coupling between source and sink organs

諏訪 竜一*; 藤巻 秀; 鈴井 伸郎; 河地 有木; 石井 里美; 阪本 浩一*; Nguyen, N. T.*; 実岡 寛文*; Mohapatra, P. K.*; Moghaieb, R. E.*; et al.

Plant Science, 175(3), p.210 - 216, 2008/09

https://doi.org/10.1016/j.plantsci.2008.03.022

Salinity stress affects photosynthate partitioning between sources and sinks of plants, but how it affects on these systems is less understood. Because sources and sinks are closely knitted, any adverse effect under sub-optimal condition on one part is often misinterpreted for the other. Knowledge on regulation of carbon partitioning is indispensable for stress resistance and good plant growth. In the present study, alteration of carbon partitioning in tomato plants (lycopersicon esculentum L. cv. Momotarou) under saline (NaCl) environment was studied by feeding radioactive C and stable C isotopes. Pulse chases were conducted for measuring spatial and temporal distributions of C. C was measured by standard conventional technique, but C distribution was monitored using by PETIS. Salt stress resulted in reduced carbon translocation towards roots. Majority of the photosynthate accumulated in the leaf. We have also observed that the reduction in translocation of carbon occurred well before salt stress symptoms of reduced photosynthesis and plant growth in salt exposed plants. The effect on sink activity also showed by decrease in stem diameter and reduced photosynthetic activity. In addition, PETIS analysis of C translocation indicates that carbon translocation to roots was inhibited under salt conditions without direct effect of leaf Na accumulation and osmotic stress These results suggest that NaCl has direct effects on plants inhibiting carbon partitioning within few hours of salt solution exposure without inhibition of source activity.