Impacts of root pruning intensity and direction on the phytoremediation of moderately Cd-polluted soil by Celosia argentea

Root pruning can impact the nutrient uptake capacity, photosynthetic efficiency, transpiration rate, root pressure, and biomass yield of various plants, which influence phytoremediation. A series of root pruning treatments with different combinations of direction (two-side pruning and four-side pruning) and intensity (10%, 25%, and 33% pruning) were performed on Celosia argentea. All two-side pruning treatments, regardless of intensity, decreased the dry biomass of the C. argentea roots at the end of the experiment relative to that of the control, and the lowest value occurred in the two-side-33% pruning treatment. However, the two-side-10% and two-side-25% pruning treatments stimulated the growth rate of the plant leaves significantly by 58.6% and 41.4%, respectively, relative to that of the control, and even offset the weight loss of the plant roots. Contrastingly, the two-side-33% pruning treatment reduced the biomass yield of leaves by 24.1%. For the four-side pruning treatments, low intensity increased the dry weight of both the plant roots and leaves, while both decreased under high intensity root pruning. The dry weight, Cd content, pigment level, and photosynthetic efficiency in the four-side-10% treatment were higher than those in the other treatments during the experiment, thereby corresponding to the best phytoremediation effect. Except for the two-side-33% pruning treatment, all the treatments increased the phytoremediation efficiency of C. argentea, thereby indicating that root pruning with a suitable combination of direction and intensity can positively influence the Cd removal ability of C. argentea.

Root pruning - a growth regulation practice in fruit crops.

Root pruning is a horticultural practice from ages ago that has potential benefits on tree crop growth regulation and production. It is followed in orchards as a growth control mechanism of vigorously growing fruit trees. The growth regulation in trees is brought about by many physiological mechanisms involving water stress and assimilates partitioning to maintain the root: shoot equilibrium. Root pruning of structural roots increases the function and efficiency of functional roots in trees. It is widely practiced in transplanting of saplings which ensures better establishment. Time and selection of the distance from the trunk by root pruning may play an important role not only on vigour control but also on vegetative response and flower induction, fruit set; hence, they should be addressed as well. However, it will require additional experience, horticultural insight and better understanding of the physiological basis of the technique. It favours the large-scale adoption of root pruning in perennial fruit crops under high-density planting system in order to regulate the canopy size and regular bearing.

Early Flare Root Development on Nursery Field-Grown Seedling Stock

Field production of seedlings used to create nursery stock liners involves transplanting and root pruning that can alter root system architecture. Seedlings of eight species of trees commonly used in urban landscapes were selected based on the configuration of their woody lateral roots; Preferred (maximum gap between roots ≤90 degrees), Acceptable (maximum gap 120–150 degrees), and Inferior (≥180 degree gap—no lateral roots on one side). The lateral root configuration (LRC) of the seedlings was compared to the LRC one year after replanting. The number of lateral or regenerated roots alone was generally adequate to form an acceptable root flare (≥3 roots) one year after seedlings were replanted. The maximum gap in lateral roots as a seedling was not consistent with the maximum gap one year after the seedlings were replanted in most species. It often became larger. Neither lateral roots nor regenerated roots alone could reliably produce a root structure with an acceptable maximum gap between roots. Lateral roots and roots regenerated from the pruned end of the main root, together produced enough flare roots one year after replanting with a small enough maximum gap in the radial distribution for good stability. This information may be an initial step in developing criteria for seedling grading systems that will improve root systems of nursery stock grown for planting in urban landscapes.

EFEITO DA PODA RADICULAR E DO HIDROGEL NO CRESCIMENTO DE MUDAS DE JATOBÁ

A produção de mudas de jatobá (Hymenaea courbaril L.) é essencial para a conservação e restituição ao seu habitat natural. Entretanto a produção de mudas de espécie nativa ainda é pouco estudada. Portanto, o objetivo deste estudo foi avaliar o efeito de diferentes níveis de poda e doses de hidrogel no crescimento inicial de jatobá sob sombreamento. Mudas de jatobá com 90 dias de idade foram usadas no experimento. O delineamento experimental foi o esquema fatorial composto de três níveis de poda radicial (0,0; 25,0 e 50,0%) e cinco doses de hidrogel (0,0; 2,0; 4,0; 6,0 e 8,0 g L-1 de substrato) totalizando 15 tratamentos. Aos 105 dias após o transplantio em casa de vegetação, foram avaliados os parâmetros morfométricos e índices de crescimento. As mudas submetidas à poda radicial de 25,0% apresentaram maior crescimento após transplantio para sacos plásticos. O hidrogel também mostrou efeito positivo nas variáveis morfométricas avaliadas. Efeitos combinados do nível de poda radicial a 25,0% e doses de hidrogel na faixa de 3,0 a 4,0 g L-1 exerceram efeitos positivos no crescimento das variáveis morfométricas. Essas técnicas isoladas ou combinadas podem ser aplicadas por viveiristas para prolongar o tempo de manutenção de mudas de jatobá.Palavras-chave: Polímero hidroabsorvente; déficit hídrico; sistema radicial; Hymenaea courbaril L. EFFECT OF ROOT PRUNING AND HYDROGEL ON GROWTH OF JATOBA SEEDLINGS ABSTRACT:The production of jatoba (Hymenaea courbaril L.) seedlings is essential for the conservation and restitution of their natural habitat. However, the production of seedlings of native species is still little studied. Therefore, the objective of this study was to evaluate the effect of different levels of pruning and hydrogel doses on the initial growth of jatoba under shading. We used jatoba seedlings with 90 days of age in a factorial scheme consisting of three levels of root pruning (0.0, 25.0, and 50.0%) and five hydrogel doses (0.0, 2.0, 4.0, 6.0 and 8.0 g L-1 substrate) totalizing 15 treatments. At 105 days after transplanting in the greenhouse, morphometric parameters and growth rates were evaluated. Seedlings submitted to root pruning of 25.0% showed greater growth after transplanting to plastic bags. The hydrogel also showed a positive effect on the morphometric variables evaluated. The combined effects of 25.0% of root pruning level and doses of hydrogel in the range of 3.0 to 4.0 g L-1 exerted positive effects on the growth of morphometric variables. These isolated or combined techniques can be employed in a nursery to prolong the maintenance time of jatoba seedlings.Keywords: Hydroabsorbent polymer; water deficit; root system; Hymenaea courbaril L.

Effects of growth control on yield and fruit quality of the apple cultivar ‘Rubin’

The effect of tree growth-control technologies on apple tree vegetative development, productivity and fruit quality was investigated with apple cultivar ‘Rubin’ on dwarf rootstock P 60 at the Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry in 2015–2018. Eight treatments were established combining tree trunk incision by chainsaw before flowering, application of prohexadione-calcium in different dose and time, summer pruning in August and root pruning before flowering. Root pruning from both sides of the tree significantly reduced tree trunk diameter, shoot length and pruning weights but at the same time reduced fruit weight. It increased tree productivity and enhanced fruit colouring. Two applications of prohexadione-calcium significantly reduced mean shoot length and increased average fruit weight. Summer pruning had a positive impact on fruit colouring. Trunk incisions enhanced leaf P, K and Fe content. Pro-Ca increased leaf Ca content. Trees root pruned from both sides had one of the lowest contents of all tested minerals. All tree growth-control technologies had a positive impact on tree productivity , fruit quality and bearing stability comparing with control treatment.