Published in Scientific Papers. Series B, Horticulture, Volume LIX
Written by Márk STEINER, Máté VÉRTESY, Magdolna SÜTÖRI-DIÓSZEGI, Károly HROTKÓ

The rate CO2-fixation of the plant depends significantly on the absorption of available photosinthetically active radiation (PAR). The PAR absorption ability is determined by the size and shape of canopy and by the position of leaves. In this context, there may be notable differences between species and moreover varieties. The aim of our work was to compare the PAR absorption ability of different Tilia varieties. Our measurements were done in Soroksár, Budapest with AccuPAR LP-80 linear ceptometer in an experimental linden alley. Beside leaf area index (LAI) the instrument is able to calculate the ratio of photosinthetically active radiation (PAR) above and below the canopy, which is the PAR transmission ability of foliage (τ). With this information the PAR absorption ability of the canopy can be easily calculated. Measurements were done monthly in 2013 (March-September) and 2014 (March-October). In the sprouting period of 2014 – to ensure better traceability – measurements were done every two weeks. From among the 13 varieties which are in the experimental alley the results of 6 varieties (Tilia americana ’Redmond’, T. cordata ’Greenspire’, T. c. ’Savaria’, T. platyphyllos ’Favorit’, T. tomentosa ’Szeleste’, T. t. ’Zentai Ezüst’) will be presented in this paper. In 2013, the PAR absorption of investigated varieties reached their maximum in the early July (68-84 %). T. americana ’Redmond’ was exception, because its maximum was in the middle of June (85 %). Then the light absorption ability of canopies decreased gradually. In 2014, after initial growing of values in the case of every varieties slight decreasing was found in early June, which reason lies in the end of blooming. Then, till the middle of June increasing values were measured again. The foliage development was monitored till the end of July, and the declining of PAR absorption was sensible in September caused by reduction of leaf area.

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