@article {51688, title = {Carbon balance of Panicum coloratum during drought and non-drought in the northern Chihuahuan desert}, journal = {Journal of Ecology}, volume = {77}, year = {1989}, month = {1989}, pages = {799-810}, abstract = {

(1) The daily C02 flux of above-ground and below-ground components of Panicum coloratum growing in the northern Chihuahuan desert was determined during a spring drought and following the autumn reproductive phase of growth. The objectives were (i) to determine the whole-plant carbon balance after a fifty-two day drought when photosynthetic capacity was severely repressed, and (ii) to determine the whole-plant carbon balance during favourable soil-water conditions prevalent after the autumn reproductive period. (2) Water stress severely repressed diurnal photosynthetic capacity during drought. The below-ground biomass, however, consisted of suberized roots with low respiratory activity. The net result was a positive whole-plant carbon gain of 2{\textperiodcentered}6 mg C g dry wt -1 day -1. \ (3) Precipitation, amounting to 1{\textperiodcentered}12 cm, ended the fifty-two-day drought, and increased the whole-plant carbon gain approximately six-fold. (4) The mean root/shoot quotient was 1{\textperiodcentered}9 during the spring drought and 0{\textperiodcentered}6 in the autumn. Reproductive tissue accounted for 13-34\% (mean= 22\%) of the above-ground biomass in the autumn. (5) Following reproductive growth, when soil-moisture conditions were favourable, the root system comprised suberized roots, non suberized nodal roots and other nonsuberized roots. Although the last two root types had high respiration rates, their presence in low quantities and low soil temperatures resulted in below-ground respiration approximately equal to that during drought. The whole-plant carbon gain during September was 17{\textperiodcentered}2 mg C g dry wt -1 day -1.

}, doi = {10.2307/2260986 }, url = {/files/bibliography/351.pdf}, author = {Sisson, W.B.} } @conference {51797, title = {Photosynthesis and water relations of mesquite and fourwing saltbush cohabiting sand dunes in the northern Chihuahuan Desert}, booktitle = {40th Annual Meeting, Society for Range Management}, year = {1987}, month = {1987}, pages = {150}, author = {Sisson, W.B. and Gibbens, Robert P.} } @booklet {51854, title = {Effects of UV-B Radiation on Photosynthesis}, volume = {NATO Advanced Science Institute Series, Ecological Science. Stratospheric Ozone Reduction, Solar Ultraviolet Radiation and Plant}, year = {1986}, month = {1986}, pages = {376 pp}, publisher = {Springer-Verlag}, address = {Berlin, Germany}, abstract = {

Several component reactions of photosynthesis, and net C02 assimilation rates have been shown to be detrimentally affected by UV-B radiation levels equal to or above those presently received at various locations on the earth{\textquoteright}s surface. Many of these studies, however, were completed under environmental conditions that deviated from ambient field conditions to such an extent that extrapolation of results for predictive purposes would probably overestimate the harmful effects of reduced atmospheric ozone levels and the concomitant increases in UV-B radiation. Nevertheless, the photosynthetic process has been shown to be sensitive to UV-B radiation and, therefore, warrants further study. The ability of plants to tolerate increased levels of UV-B radiation, relative to photosynthetic capacity, may be dictated by acclimation processes that would intensify UV-B attenuation prior to its absorbance by sensitive components or reactants of photosynthesis

}, url = {/files/bibliography/302.pdf}, author = {Sisson, W.B.}, editor = {Worrest, R.C. and Caldwell, M. M.} } @article {51855, title = {Seasonal nitrate reductase activity of three genotypes of Atriplex canescens in the northern Chihuahuan Desert}, journal = {Journal of Ecology}, volume = {74}, year = {1986}, month = {1986}, pages = {579-589}, abstract = {

(1) Seasonal nitrate reductase (NR) activity of the young, uppermost leaves of three genotypes (diploid, tetraploid and hexaploid) of Atriplex canescens growing in situ showed maximal activity during reproductive growth. Because rainfall coincided with reproductive growth, higher NR activity during this period may have been due to new leaf growth and increased soil-NO3) availability rather than an increased need for nitrogen due to developing seeds. The wing-like bracts of the immature fruits possessed NR and may have been a source of reduced nitrogen for seeds. (2) Seasonal leaf water content was significantly correlated with NR activity in all genotypes, and water potentials in the stem xylem were correlated with NR activity only in the tetraploid plants. (3) In a glasshouse the hexaploid plants had significantly higher NR activity and reduced-nitrogen concentrations than did either the diploid or tetraploid plants. (4) Although thermal adaptation of NR would be advantageous for plants inhabiting a desert environment where seasonal temperatures fluctuate widely, there was no evidence to suggest that acclimation of NR occurs in A. canescens growing in situ.

}, doi = {10.2307/2260275 }, url = {/files/bibliography/303.pdf}, author = {Sisson, W.B. and Throneberry, G.O.} } @proceedings {51896, title = {CO2 exchange of the above-ground and below-ground components of Kleingrass (Panicum coloratum L.) during drought in the northern Chihuahuan Desert}, year = {1985}, month = {1985}, pages = {336-338}, address = {Kyoto, Japan}, abstract = {

The effect a 52 day drought had on the die! whole-plant carbon balance of kleingrass (Panicum coloratum L.) growing in the northern Chihuahuan desert was determined. Whole-plant C02 inputs (photosynthesis) and outputs (belowground and aboveground respiration) were measured on day 52 of the drought (June 23, 1981) and 2 days following 1.12 cm of precipitation that occurred on June 24, 1981.

}, keywords = {carbon balance, desert, drought, photosynthesis, root respiration}, url = {/files/bibliography/282.pdf}, author = {Sisson, W.B.} } @proceedings {51925, title = {Seasonal leaf nitrate reductase activity, nitrogen and nitrate content, and water relations of Atriplex canescens (Pursh) Nutt. in the northern Chihuahuan Desert}, year = {1984}, month = {1984}, pages = {133-137}, publisher = {Intermountain Forest and Range Experiment Station, General Technical Report INT-172}, address = {Provo, UT}, abstract = {

Seasonal nitrate reductase (NR) activity of young, uppermost leaves of Atriplex canescens (Pursh)Nutt. (diploid genotype) growing in situ was maximal during reproductive growth. Because precipitation on the study site coincided with reproductive growth, higher NR activity during this periods may have been due to new leaf growth and increased soil NO3 availability rather that the nitrogen sink in developing seeds. Seasonal leaf water content (percent) was significantly ( P \< 0.10 ) correlated with NR activity. Stem xylem water potentials were not correlated with NR activity. Although thermal adaptation of NR would, in general, be advantageous for plants inhabiting a desert environment with widely fluctuation seasonal temperatures, there was no evidence to suggest that acclimation of NR occurs in A. canescens growing in situ.

}, url = {/files/bibliography/270.pdf}, author = {Sisson, W.B. and Throneberry, G.O. and Southward, G.M.}, editor = {Tiedemann, Arthur R. and McArthur, E. Durant and Stutz, Howard C. and Richard Stevens and Kendall L. Johnson} } @article {51971, title = {Carbon balance of Yucca elata Engelm. during a hot and cool period in situ}, journal = {Oecologia}, volume = {57}, year = {1983}, month = {1983}, pages = {352-360}, abstract = {

Respiratory activity of intact, attached roots was measured under field and controlled conditions. Root respiration of Yucca elata Engelm. was highly temperature dependent: Q10 values decreased from 2.1 (12-22{\textdegree} C) to 1.7 (26-36{\textdegree} C) as temperatures increased. Respiration ceased after 5 h at 42{\textdegree} C. In the field, in August, when net leaf photosynthesis was severely depressed, the die! fluctuation in the respiration rate of suberized and partially suberized roots was predominantly a function of temperature. A photoperiod-associated rise in respiration rates apart from temperature response occurred in February for nonsuberized, partially suberized, and suberized roots when active net photosynthesis occurred throughout the photoperiod. In whole-plant root systems, respiratory C02 was 3.2 and 4.3 mg C02. g Dw -1. d -1 in August and February, respectively, when adjusted for the proportion of suberized and nonsuberized lateral roots. On a whole-plant basis, 0.89 mg C {\textperiodcentered} g DW -1 {\textperiodcentered} d -1 was gained during February and 0.46 mg C {\textperiodcentered} g DW -1 {\textperiodcentered} d -1 was lost in August. The belowground: above ground ratio of whole-plants in situ was 0.42 on a shallow soil where vertical root growth was limited to a soil depth of 68 cm and ranged from 1.29 to 5.94 (.X= 3.31) in deep sands. No leaf dark fixation of C02 was observed in field plants during August and February, nor in well-watered plants or plants subjected to drought in laboratory studies. Although small die! fluctuations in leaf acidity occurred in both field and greenhouse-grown plants, results of this study suggest that Y. elata is a C3 plant.

}, url = {/files/bibliography/246.pdf}, author = {Sisson, W.B.} } @article {51970, title = {Effects of UV-B radiation on higher plant photosynthesis}, year = {1983}, month = {1983}, pages = {16 }, keywords = {effects, higher plant, photosynthesis, UV-B radiation}, author = {Sisson, W.B.} } @conference {52017, title = {Effect of defoliation and ambient temperature on photosynthesis and diurnal root respiration of Kleingrass (Panicum coloratum L.) in the field}, booktitle = {35th Annual Meeting, Society for Range Management}, year = {1982}, month = {1982}, author = {Sisson, W.B.} } @article {52055, title = {Absorption of SO2 by pecan (Carya illinoensis [Wang] K. Koch) and alfalfa (Medicago sativa L.) and its effect on net photosynthesis}, journal = {Journal of Experimental Botany}, volume = {32}, year = {1981}, month = {1981}, pages = {523-534}, url = {/files/bibliography/206.pdf}, author = {Sisson, W.B. and Booth, J.A. and Throneberry, G.O.} } @article {52057, title = {Photosynthesis, growth and ultraviolet irradiance absorbance of Cucurbita pepo L. leaves exposed to ultraviolet-B radiation (280-315 nm)}, journal = {Plant Physiology}, volume = {67}, year = {1981}, month = {1981}, pages = {120-124}, url = {/files/bibliography/204.pdf}, author = {Sisson, W.B.} } @conference {52056, title = {Responses of photosynthesis and root respiration to temperature, soil moisture and defoliation}, booktitle = {New Mexico State University, Agriculture Experimental Station Special Report 41}, year = {1981}, month = {1981}, pages = {37}, abstract = {Respiration processes associated with growth and maintenance of perennial plant root systems represent a significant investment of reserve nutrients since root:shoot ratios are often reater than 1. The replenisment of these reserves for aboveground and belowground plant growth through photosynthesis is often limited in semidesert rangelands by low soil moisture, high temperatures, and defoliation of photosynthetic tissue. Although photosynthesis has been quantified for a number of forage species, there is presently no information regarding reserve substrate costs (in the form of CO2 respired) for root systems of plants in a field situation. Thus, several ongoing studies were designed to define the substrate costs involved in producing and maintaining aboveground and belowground plant components and the concommitant replenishment of these reserves through photosynthesis. The important interactions of soil and air temperature, soil moisture, and defoliation are also being studied. Photosynthesis by soap tree yucca leaves provide substrates for growth of new roots and maintenance of old roots. Initial results using soap tree yucca indicate that root respiration is linearly increased by soil temperature and a doubling of rates occurs for every 10-{\textdegree}C-increase in temperature. This type of response occurs during dark periods or when photosynthesis is suppressed by either high temperature or water stress. During periods of minimal water stress and cooler air temperatures when high rates of photosynthesis occur, a photoperiod-associated rise in root respiration beyond a simple temperature response occurs. Field studies using Kleingrass show similar types of response to temperature and soil moisture. A reduction in root respiration rates following defoliation is probably associated with root growth cessation. Future research will be designed to determine physiological tolerances of important range forage species to defoliation. The approach involves, among other physiological parameters, a quantification of reserve substrates relative to environmental variables, defoliation, regrowth, and substrate gains (photosynthesis) and losses (aboveground and belowground respiration).}, keywords = {defoliation, photosynthesis, root respiration, soil moisture, temperature}, url = {/files/bibliography/205.pdf}, author = {Sisson, W.B.} } @conference {52103, title = {Absorption of SO2 by pecan (Carya illinoensis [Wang] K. Koch) leaflets and its effect on photosynthesis}, booktitle = {Plant Physiology}, volume = {65}, year = {1980}, month = {1980}, pages = {49}, author = {Sisson, W.B. and Throneberry, G.O. and Booth, J.A.} } @conference {52105, title = {Ambient temperature effects on photosynthesis and root respiration of intact Yucca elata Engelm}, booktitle = {Plant Physiology}, volume = {65}, year = {1980}, month = {1980}, pages = {Abstract 48}, author = {Sisson, W.B.} } @inbook {52104, title = {Carbon dioxide exchange of Yucca elata Engelm: Effect of temperature on photosynthesis and root respiration}, booktitle = {Yucca}, year = {1980}, month = {1980}, pages = {35-50}, publisher = {Centro de Investigacion en Quimica Aplicada}, organization = {Centro de Investigacion en Quimica Aplicada}, address = {Saltillo, Coahuaca, Mexico}, keywords = {carbon dioxide exchange, photosynthesis, root respiration, Yucca elata Engelm}, author = {Sisson, W.B.} } @proceedings {52133, title = {Carbon dioxide exchange of Yucca elata Engelm: effect of temperature on photosynthesis and root respiration}, year = {1979}, month = {1979}, address = {Saltillo, Coahuaca, Mexico}, keywords = {carbon dioxide exchange, photosynthesis, root respiration, Yucca elata Engelm}, author = {Sisson, W.B.} } @conference {52132, title = {Photosynthesis, growth, and UV irradiance absorbance of Cucurbita pepo leaves exposed to UV-B radiation (280-315 nm)}, booktitle = {Western Section of the American Society for Plant Physiology}, year = {1979}, month = {1979}, address = {Reno, NV}, author = {Sisson, W.B.} } @conference {52191, title = {Solar radiation as a detrimental factor to photosynthesis and growth in Rumex patientia L.}, booktitle = {30th Annual Meeting, Society for Range Management}, year = {1977}, month = {1977}, pages = {30}, keywords = {photosynthesis, Rumex patientia, solar radiation}, author = {Sisson, W.B.} } @conference {52190, title = {UV-B radiation effects on photosynthesis and plant growth}, booktitle = {Research Symposium, UV-B Radiation: Biological and Climatic Effects Workshop}, year = {1977}, month = {September 19-21,}, address = {University of Maryland}, author = {Sisson, W.B.} }