Main Transport Pathways Research Articles

Characterization of Potassium Uptake and Translocation in Soybeans

AbstractNutrients taken up by plant roots are translocated and distributed to plant parts in order for the plant to carry on its normal functions. To understand these functions better, we developed a five compartment mathematical model which describes K translocation within soybean [Glycine max (L.) Merrill] plant parts during vegetative and reproductive growth. The instantaneous rate of change of K contents in the five‐compartment soil‐soybean system was described using mass balance equations. The seasonal dry matter accumulation, nutrient concentrations, and nutrient contents of the stems, branches, leaves, and pods were used as inputs into the model to determine the effect of growth stage on uptake and translocation parameters. Among the various plant parts, the maximum K fluxes were in the pods (0.257 g m−2 d−1) followed by the branches (0.191 g m−2 d−1), the stems (0.118 g m−2 d−1), and the leaves (0.108 g m−2 d−1). The maximum fluxes of K for the stems, branches, and leaves were reached at the same time during vegetative growth. In general, K uptake was higher during vegetative than during reproductive growth. The magnitudes of the transport coefficients were variable during the growing season. During vegetative growth the highest K transport coefficient (15.18 g m−2 d−1) was from the stem to the branches indicating that the main transport pathway of K was from the stem to the branch. During reproductive growth the highest transport coefficient (23.26 g m−2 d−1) was from the stem to the pods which means that the major movement of K between plant parts during this time was from the stem to the pod. Transport coefficients of K between the branches and pods were low. These results show that the net fluxes of K in soybeans varies with transport pathway within the plant and with plant age.

A long range seismic-recording buoy

The transport of Pacific-origin water across the eastern Chukchi Sea during summer is studied using shipboard hydrographic and Acoustic Doppler Current Profiler data from multiple surveys. The study identifies two major transport pathways in this region. The well-known Alaskan Coastal Current (ACC) flows poleward along the Alaska coast, while a more recently discovered and slower current flows northward through the Central Channel between Herald and Hanna Shoals. The two currents separate past Point Hope and appear to merge again in Barrow Canyon via previously unresolved pathways flowing west to east across the Chukchi Sea. The collective flow that transports Pacific water from Bering Strait to Barrow Canyon is termed the Bering to Barrow Current System (BBCS). The coastal branch of the BBCS, which encompasses the ACC, is a weakly baroclinic flow with a maximum speed in excess of 80 cm/s inside Barrow Canyon. The Central Channel branch of the BBCS is considerably weaker, with a maximum flow speed under 20 cm/s. A portion of the Pacific water that flows towards Herald Canyon to the west may also contribute to the BBCS, the amount, but the amount is within the margin of error of our data. The difference in the advective time scales of the various branches allows water masses of different seasonal characteristics to be transported simultaneously by the BBCS. Summer water masses occupy most of the southern and central Chukchi Sea while winter water masses occupy Hanna Shoal and shelfbreak regions in the northern Chukchi Sea during summer. The total BBCS volume transport in summer is measured at four different locations in the eastern Chukchi Sea and found to be generally consistent. The overall mean transport is 0.86 Sv, compared to the summer Bering Strait transport of 1.08 Sv. This study suggests that the BBCS is the main transport pathway delivering Pacific water masses into the western Arctic Basin.