Calcium (Ca) in plants has essential roles related to tissue mechanical strength and plant tolerance to stress, and understanding what affects its translocation and partition is of high value. Ca was shown to accumulate in transpiring organs and is considered to be coupled to water transport. However, being translocated mostly in the xylem, a conduit under tension, en-route sampling cause cessation of flow yielding fragmented understanding. To enable in-vivo, real time exploration of the coupling hypothesis, we developed and used a noninvasive sensing system to track translocation of gamma emitting Sr, an accepted Ca tracer, together with transpiration measurements. Tomato seedlings were grown in a continuously aerated hydroponic solution under controlled climatic conditions. Having three fruit bearing trusses, plants were moved to a growth room and arranged in pairs were one plant was continuously weighted and the other installed with high sensitivity gamma radiation detectors at various locations. A mixture of 85Sr and 88Sr was added to the solution of the 2nd plant around noon and has been followed for several days. Root applied Sr showed a fast sequential arrival to the main stem detectors along the expected water flow path. During the first few days, early morning transpiration and Sr translocation seemed to be coupled while later in the day a complex pattern emerged probably due to absorption-desorption dynamics as well as loading-unloading activity. As days passed, upstream radiation levels declined while downstream terminal organs levels increased, showing long-term accumulation pattern there. Fruit radiation pattern showed day inflow, which contradicts with the accepted fruit night-fill of xylem-borne ions. Fruit maturity is suggested as a possible explanation. Our custom made system, having both spatial and temporal capabilities, enabled following translocation patterns of radio-Sr within the plant. Together with indicative transpiration measurements, interesting insights were gained in reference to Ca-water coupling.

The independent effects of irrigation solution N, P and K concentrations on flowering and fruit set in olive trees (Olea europaea L. cv. Barnea) were studied over two successive seasons in a container experiment. Treatments included eight levels of N ranging from 5 to 202 ppm, seven levels of P from 0.2 to 20 ppm and seven levels of K from 10 to 208 ppm. At low concentrations of each of the minerals, additions led to large increases in their contents in leaves and, as the concentrations became high, relative increases in leaf accumulation were reduced. Availability of both N and P was found to influence flowering intensity in the olive trees while K had only a minor affect. Fruit set was affected by both N and P but not K levels. Total fruit load of olives was a function of combined flowering and fruit set levels. Fruit load increased to a maximum as leaf N increased from 0.8% to 1.77-1.56% and then decreased as leaf N increased to 2.1%-1.8% (2007 and 2008 respectively). The number of olives per tree increased appreciably as leaf P increased from minimum levels and relative increases in fruit load tapered at the highest measured leaf contents. Maximum fruit load was found corresponding to approximately 0.2% P. Fruit load was not influenced by leaf K concentration. The findings indicate that N and P play fundamental roles in processes affecting olive-tree productivity.