Cropping intensity and rainfall effects on upland rice yields in northern Laos |
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| Authors: | K Saito B Linquist B Keobualapha K Phanthaboon T Shiraiwa T Horie |
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| Institution: | (1) Centre for Research in Plant Science, University of the West of England, Coldharbour Lane, BS16 1QY Bristol, UK;(2) Dipartimento di Gestione dei Sistemi Agricoli e Forestali, Facoltà di Agraria, Università degli Studi “Mediterranea” di Reggio Calabria, località Feo di Vito, 89060 Reggio Calabria, Italy;(3) Dipartimento di Biotecnologie Agrarie, Agripolis, Università di Padova, Viale dell’Università 16, I-35020 Legnaro Padova, Italy;(4) Present address: School of Biological Sciences, University of East Anglia, NR4 7TJ Norwich, UK |
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| Abstract: | Two fractions of earthworm humic substances, differing in nominal molecular weight, containing a very low amount of free IAA,
and exhibiting auxin-like properties, were prepared and characterised by infrared and 1H-NMR spectroscopy. In this study we investigate their effects on stomatal opening, as influenced by phospholipase A2, in leaf of the Argenteum mutant of pea (Pisum sativum L.) Both of the humic fractions caused stomatal opening in the epidermal peels. The response showed a broad biphasic dose
dependence and the effective concentrations were similar for the two fractions. The maximal stomatal apertures in response
to both humic substances were similar to that caused by IAA and somewhat less than the response to white light or fusicoccin.
Two inhibitors of phospholipase A2 selectively blocked the response of stomata to both IAA and humic substances, without affecting the response to light or
fusicoccin. We conclude that stomatal opening in response to auxin and humic substances involves activation of a phospholipase
A2 that is not involved in signalling the response to light or fusicoccin. |
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| Keywords: | auxin fusicoccin humic substances light phospholipase A2 stomata |
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