ROOT PRUNING EFFECTS ON GROWTH AND STAND ESTABLISHMENT RATE OF CUCUMBER GRAFTED SEEDLINGS

Abstract

A commercial cucumber (Cucumis sativum) variety was grafted onto a commercial rootstocks (Cucurbita maxima × C. moschata). Two different grafting methods; splice grafting (SG) and root pruned splice grafting (RPSG) were simultaneously applied. The relative growth rate during the nursery stage (RGR) and its components, net assimilation rate (NAR) and leaf area ratio (LAR) were computed for each experimental plot. Meantime, root-shoot allometry coefficients were calculated for each experimental unit. Additionally to that, equal amounts of fresh roots originating from both grafting methods were washed out carefully with tap water and immersed into equal quantities of methanol. Several diluted solutions were prepared out of it and rooting index of 20 day old cuttings of tepary bean (Phaseoulus acutifolius), was used to indicate the presence of growth hormones extracted from fresh rootstock roots. End of nursery period, over hardened seedlings (40 day after grafting) of both grafting methods, together with non grafted seedlings with similar age, were transplanted in a plastic greenhouse. Plant height was successful measured and the slope of respective growth curves, was calculated as an indication of plant stand establishment rate. Compared to root pruned splice grafted seedlings (RPSG), a higher plant dry matter and larger leaf area per plant was recorded for splice grafted seedlings (SG) at the end of nursery stage. Despite that, a significantly higher relative growth rate was found for root pruned splice grafted seedlings, mostly due to higher net assimilation rate. Most of plant assimilates were allocated to the growth of new root system. A higher concentration of plant growth hormones was indicated by a higher rooting index of Phaseoulus acutifolius, in case of root pruned grafted seedlings, and to that is attributed the significantly higher stand establishment rate of root pruned grafted seedlings, versus splice grafted seedlings after transplanting.