|Authors: ||I. Grāvīte, E. Kaufmane|
|Keywords: ||Prunus domestica L., abiotic stress, chlorophyll content index, chlorophyll a fluorescence, performance index, RC/ABS index|
Climate change and the meteorological conditions during the winter have severely negative impact on the quality of the plum orchards.
It is necessary to increase the winter hardiness of plum trees and buds as influenced by abiotic and biotic factors.
Balanced composition of nutrients is important.
High fluctuations of temperatures occur in winter during recent years, resulting in bud damage and even tree losses.
Calcium (Ca) and boron (B) can have a significant impact on both plant vegetative growth and generative development.
The aim of the study was to determine influence of the foliar sprays of Ca and B on plant photochemical activity, reducing the stress caused by environmental factors.
In order to determine the changes caused by fertilizers, the following were determined: chlorophyll content index (CCI) and parameters of fluorescence: Fv/Fm (the ratio of variable fluorescence (Fv) to maximum fluorescence value (Fm)); plant performance index (PI) and density of active reaction centres as ratio RC/ABS which characterizes the number of active photochemical performance of photosystem II (PSII) reaction centres in respect to the quantity of light absorbed.
The investigation was done at the Latvia State Institute of Fruit Growing with the Latvian plum cultivars 'Sonora' and 'Lase', and as a control, 'Duke of Edinburgh' (syn. 'Prince of Wales') was used.
Boron and calcium foliar sprays were used in the period from 2011 to 2013. High variation was found for fluorescence parameters between foliar sprays.
There were statistically significant differences of mean values of Fv/Fm, RC/ABS and PI. Evaluation of the plant photosynthesis processes (chlorophyll a concentration index and fluorescence indices) showed that plants treated by boron foliar sprays had better regeneration after the stresses caused by agro-climatic factors, their intensity of vegetative growth was lower after the beginning of fruit production in comparison with other variants.
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