ISHS Acta Horticulturae 455: V International Mango Symposium
PHOTOINHIBITION OF PHOTOSYNTHESIS IN MANGO LEAVES: EFFECT OF CHILLY NIGHTS |
| Authors: | G. Nir, K. Ratner, Eugene E. Gussakovsky, Y. Shahak |
| Keywords: | chlorophyll fluorescence, stomatal resistance, Mangifera indica, peach, papaya |
| Abstract:
Photoinhibition of photosynthesis (PI, light stress) is a process by which excessive light radiation which is absorbed by the leaves, results in the inactivation and/or impairment of the chlorophyll-containing reaction centers of the chloroplasts, thus inhibiting photosynthesis. The susceptibility of leaves to photoinhibition is known to be enhanced by additional stress factors which coincide with the light. Here we describe the effect of chilling temperatures which are imposed on the tree prior to light exposure. We have found that chilly nights markedly enhance photodamage which develops in sun-exposed mango leaves on the following day. Photoinhibition was monitored by the decrease in photosystem II quantum efficiency, as detected by the chlorophyll fluorescence parameter Fv/Fm, as well as by gas exchange. Characterization of the chilly-night-sunny-day phenomenon revealed the following properties: (i) The effect of the chilly night is expressed in sun-exposed, but not in shaded leaves; (ii) The daily PI which develops after warm nights is fully reversible, while after chilly nights it is mostly irreversible; (iii) The photoinhibitory damage gradually accumulates during repetitive cycles of chilly nights - sunny days; (iv) Chilly nights also cause the reduction of CO2 uptake capacity and stomatal conductance. (v) The chilly night effect on PI occurs in subtropical/tropical trees such as mango and papaya, to a lesser extent in citrus, while not at all in peach leaves. | |
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