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Movement of Water and Solutes in Sieve Tubes of Willow in Response to Puncture by Aphid Stylets. Evidence against a mass flow of solution (1969)

Peel, A. J. ; Field, R. J. ; Coulson, C. L. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

Physiologia plantarum 22 (1969), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Experiments are described in which bark strips of willow were sealed to polythene tubes having two compartments. This allowed investigations to be made of the transport along the sieve tubes of tritiated water, 14C-labelled sugars, and 32P-phosphates from one compartment, towards a stylet situated in the bark over the other compartment.Although activity from both 14C and 32p was detected in the stylet exudate usually within 1 hour from isotope application, tritium activity was never detected even after a period of 8 hours in most experiments, though in certain cases, very low activities were detected after 4 hours. Subsequent experiments in which stylets were sited over both compartments showed that tritium activity moved laterally into the punctured sieve element more rapidly than either 14C or 32P. Experiments using both live and dead bark in which stylets were not employed, showed that within 4 hours tritium activity had moved by diffusion along the whole length of a bark strip, therefore after this time tritium activity could have moved into the stylet exudate by a diffusional process.The lack of rapid longitudinal movement of tritiated water along the sieve tubes, indicates that the transport process is unlikely to be a mass flow of solution.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1399-3054.1969.tb07435.x

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Simply Obtained Global Radiation, Soil Temperature and SoilMoisture in an Alley Cropping System in Semi-Arid Kenya (2000)

Mungai, D. N. ; Stigter, C. J. ; Coulson, C. L. ; [et al.]

Springer

Theoretical and applied climatology 65 (2000), S. 63-78

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ISSN: 1434-4483

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences , Physics

Notes: Summary Global radiation, soil temperature and soil moisture data were obtained from a 4–6 year old Cassia siamea/maize (CM) alley cropping (or hedgerow intercropping) system, at a semi-arid site at Machakos, Kenya, in the late eighties. With the growing need to explore and manage variations in agro-ecosystems these results deserve new attention. They quantify, in a simple but detailed manner, the influence of hedgerows on the microclimate of their intercrop and for comparison provide a sole maize (SM) control. Due to inhomogeneity of Cassia and maize, as well as limited budgets, the sampling methodology and the choice of appropriate equipment, including the sensors, demanded special attention. The diurnal patterns of soil temperatures at 7.5 cm depth represented well the shading patterns of the hedgerows. This can be developed into an operational auxiliary methodology of integrated shade quantification. With proper precautions, the developed sampling methodologies showed appropriately the time integrated values of the three microclimatic parameters with enough detail to understand yield differences between treatments and between rows. This approach may therefore be recommended for on-farm quantification of even greater spatial variability of parameters. The limitations of the selected methods are highlighted. Experiences with some alternative methods are also discussed.