Mathematical simulations of nitrous

No abstract

A large lecture introductory course at Iowa State University has used a forecasting activity since 1993 to actively engage students in doing science. This automatically scored Web-based activity requires students to evaluate selected weather parameters and to also select appropriate physical reasons for their values. Participants can select from more than 1000 cities in the United States for their forecast city. This activity engages students in doing what practicing meteorologists do. Further, forecast scores demonstrate increased understanding throughout the course. Design considerations were based on constructivist learning theory in order to address goals articulated by national panels; to promote problem solving, collaboration, and communication skills by being involved in scientific inquiry.

Leaf structure and water content constitute major factors affecting the interaction of radiant energy with leaves in the wavelength region from 800 to 2,600 mµ. Reflectivity, Rλ, and transmissivity, T», were measured in this wavelength region for leaves from three crop species (corn, Zea mays; soybean, Glycine max; sorghum, Sorghum bicolor). Absorptivity, Aλ, was calculated from measurements of Rλ and Tλ. The spectral responses (R», Tλ, or Aλ ) at six wavelengths (maxima and minima of the reflectivity curve) regressed on relative leaf water content (RWC) and specific leaf densities (mg/cm3) were highly correlated. A highly significant relationship between leaf RWC and the spectral response (RΔλ) over lour wide‐wavelength intervals is also reported.

Remote sensing techniques have been suggested as a possible tool to the agricultural research worker. In addition, plant leaf temperatures (a quantity capable of being measured by remote sensors) give an indication of the plant's response to the environment. For these reasons, an experiment was conducted in the field to investigate the relations between plant leaf temperatures and soil moisture stress and various environmental parameters. Leaf temperatures (TL) of two soybean [Glycine max (L.) Merr.] varieties grown under controlled irrigation were measured with an infrared thermometer during a 9‐day experiment. On a given day relative leaf water content (RWC) and TL were highly correlated. When TL's were examined over different days, vapor pressure deficit (VPD) and air temperature (TA) were found to affect TL· TL increased with decreasing values of both RWC and VPD. Interactions involving both VPD and TA with RWC were observed. TL increased with increasing TA; however, the amount of increase of TL seemed related to the leaf's level of RWC. This was related to increased transpirational cooling (stomatal conductivity) at higher levels of TA. The two varieties in this experiment were significantly different with respect to TL, but the degree of significance was related to VPD.