Search NASA⌕ Search

SEARCH · Search NASA

Results for “Plant Leaves/physiology”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

5 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Incorporation of measured photosynthetic rate in a mathematical model for calculation of non-structural saccharide concentration

A simple mathematical model for calculating the concentration of mobile carbon skeletons in the shoot of soya bean plants [Glycine max (L.) Merrill cv. Ransom] was built to examine the suitability of measured net photosynthetic rates (PN) for calculation of saccharide flux into the plant. The results suggest that either measurement of instantaneous PN overestimated saccharide influx or respiration rates utilized in the model were underestimated. If neither of these is the case, end-product inhibition of photosynthesis or waste respiration through the alternative pathway should be included in modelling of CH2O influx or efflux; and even if either of these is the case, the model output at a low coefficient of leaf activity indicates that PN still may be controlled by either end-product inhibition or alternative respiration.

NASA Program CELSS↗
NASA NTRS2001

Machine vision guided sensor positioning system for leaf temperature assessment

A sensor positioning system was developed for monitoring plants' well-being using a non-contact sensor. Image processing algorithms were developed to identify a target region on a plant leaf. A novel algorithm to recover view depth was developed by using a camera equipped with a computer-controlled zoom lens. The methodology has improved depth recovery resolution over a conventional monocular imaging technique. An algorithm was also developed to find a maximum enclosed circle on a leaf surface so the conical field-of-view of an infrared temperature sensor could be filled by the target without peripheral noise. The center of the enclosed circle and the estimated depth were used to define the sensor 3-D location for accurate plant temperature measurement.

NASA Discipline Life Support Systems↗
NASA NTRS1996

Quantifying energy and mass transfer in crop canopies: sensors for measurement of temperature and air velocity

Here we report on the in situ performance of inexpensive, miniature sensors that have increased our ability to measure mass and energy fluxes from plant canopies in controlled environments: 1. Surface temperature. Canopy temperature measurements indicate changes in stomatal aperture and thus latent and sensible heat fluxes. Infrared transducers from two manufacturers (Exergen Corporation, Newton, MA; and Everest Interscience, Tucson, AZ, USA) have recently become available. Transducer accuracy matched that of a more expensive hand-held infrared thermometer. 2. Air velocity varies above and within plant canopies and is an important component in mass and energy transfer models. We tested commercially-available needle, heat-transfer anemometers (1 x 50 mm cylinder) that consist of a fine-wire thermocouple and a heater inside a hypodermic needle. The needle is heated and wind speed determined from the temperature rise above ambient. These sensors are particularly useful in measuring the low wind speeds found within plant canopies. 3. Accurate measurements of air temperature adjacent to plant leaves facilitates transport phenomena modeling. We quantified the effect of radiation and air velocity on temperature rise in thermocouples from 10 to 500 micrometers. At high radiation loads and low wind speeds, temperature errors were as large as 7 degrees C above air temperature.

NASA Program CELSS↗
NASA NTRS1993

Supraoptimal carbon dioxide effects on growth of soybean [Glycine max (L.) Merr.]

In tightly closed environments used for human life support in space, carbon dioxide (CO2) partial pressures can reach 500 to 1000 Pa, which may be supraoptimal or toxic to plants used for life support. To study this, soybeans [Glycine max (L.) Merr. cvs. McCall and Pixie] were grown for 90 days at 50, 100, 200, and 500 Pa partial pressure CO2 (500, 1000, 2000, and 5000 ppm). Plants were grown using recirculating nutrient film technique with a 12-h photoperiod, a 26 degrees C/20 degrees C thermoperiod, and approximately 300 micromoles m-2 s-1 photosynthetic photon flux (PPF). Seed yield and total biomass were greatest at 100 Pa for cv. McCall, suggesting that higher CO2 levels were supraoptimal. Seed yield and total biomass for cv. Pixie showed little difference between CO2 treatments. Average stomatal conductance of upper canopy leaves at 50 Pa CO2 approximately 500 Pa > 200 Pa > 100 Pa. Total water use over 90 d for both cultivars (combined on one recirculating system) equalled 822 kg water for 100 Pa CO2, 845 kg for 50 Pa, 879 kg for 200 Pa, and 1194 kg for 500 Pa. Water use efficiences for both cultivars combined equalled 3.03 (g biomass kg-1 water) for 100 Pa CO2, 2.54 g kg-1 for 200 Pa, 2.42 g kg-1 for 50 Pa, and 1.91 g kg-1 for 500 Pa. The increased stomatal conductance and stand water use at the highest CO2 level (500 Pa) were unexpected and pose interesting considerations for managing plants in a tightly closed system where CO2 concentrations may reach high levels.

NASA Discipline Life Support Systems↗
NASA NTRS2005

Effects of artificial defoliation of pines on the structure and physiology of the soil fungal community of a mixed pine-spruce forest

Loss of photosynthetic area can affect soil microbial communities by altering the availability of fixed carbon. We used denaturing gradient gel electrophoresis (DGGE) and Biolog filamentous-fungus plates to determine the effects of artificial defoliation of pines in a mixed pine-spruce forest on the composition of the fungal community in a forest soil. As measured by DGGE, two fungal species were affected significantly by the defoliation of pines (P < 0.001); the frequency of members of the ectomycorrhizal fungus genus Cenococcum decreased significantly, while the frequency of organisms of an unidentified soil fungus increased. The decrease in the amount of Cenococcum organisms may have occurred because of the formation of extensive hyphal networks by species of this genus, which require more of the carbon fixed by their host, or because this fungus is dependent upon quantitative differences in spruce root exudates. The defoliation of pines did not affect the overall composition of the soil fungal community or fungal-species richness (number of species per core). Biolog filamentous-fungus plate assays indicated a significant increase (P < 0.001) in the number of carbon substrates utilized by the soil fungi and the rate at which these substrates were used, which could indicate an increase in fungal-species richness. Thus, either small changes in the soil fungal community give rise to significant increases in physiological capabilities or PCR bias limits the reliability of the DGGE results. These data indicate that combined genetic and physiological assessments of the soil fungal community are needed to accurately assess the effect of disturbance on indigenous microbial systems.

Pinus/growth & development/physiology↗