During the past decade virtually all undergraduate programs in the agricultural sciences in the U.S. have been revised. The revisions were caused by many factors, including large increases in student numbers, changes in the background of students (e.g., rural vs. urban), environmental concerns and changing agricultural technology. The purpose of this article is to suggest the need for further revision to broaden the curriculum and its students in order to meet the challenges they will face in the years ahead.
Static solution culture systems are widely used in plant research and for teaching demonstrations of plant nutrient deficiency symptoms. Numerous systems have been described (1,2) including one (3) constructed of readily available materials. Reported here is another design for a static solution culture system built of readily available components. This system is characterized by a) low cost, b) simplicity, c) easy assembly, d) potential for variable spacing of culture vessels, e) identical aeration rate for each vessel without individual air flow valves, and f) aeration from the top of the culture vessel rather than the bottom, eliminating drainage through aeration lines should the air supply fail.
Geranium seedlings (Pelargonium × hortorum L.H. Bailey ‘Mustang’) were greenhouse-grown at a plant density (PD) of 85, 170, 255, or 340 plants/m2 for two time periods (21 to 34 days and 35 to 62 days from sowing). There was a positive linear regression between PD and crop productivity (CP), expressed as g dry matter/day per m2; between PD and crop productivity efficiency (CPE), expressed as percent of energy in the photosynthetic photon flux (PPF) incident on the crop that is stored in crop dry matter as energy of combustion; and between PD and leaf area index (LAI) for both time periods. Plant top dry weight, leaf area, length of longest petiole, and main stem length and height were not affected by PD at 35 days from sowing. However, at 63 days from sowing there was a negative linear regression between PD and both plant top dry weight and main stem length, and a positive linear regression between PD and both plant height and length of the longest petiole.
Calcium deficiency symptoms of heartleaf philodendron (Philodendron scandens ssp. oxycardium) were reported to occur first on the vine's basal leaves, with the tip or uppermost leaves the last to develop symptoms (1). This pattern of symptom development was interpreted to indicate that philodendron was an exception to the generalization that Ca is immobile in plants, i.e., in philodendron, Ca was translocated from basal to upper leaves (5). Since Ca deficiency symptoms occur in meristematic areas (such as shoot and root tips), Ca is considered immobile in plants (2). Thus, the report of Ca deficiency symptoms on basal leaves of philodendron (1) was indeed exceptional. Unfortunately, there was no report of the recovery of the deficient plants when fertilized with Ca, nor any Ca analysis of philodendron tissue, to confirm that Ca deficiency was the cause of the observed symptoms (1) and to support the conclusion that Ca was mobile (5). The purpose of this study was to produce Ca deficiency symptoms in heartleaf philodendron to determine if Ca deficiency symptoms occur on basal leaves, as originally reported (1).