Adubação, níveis crescentes de irradiância nas plantas matrizes e uso do aib nas estacas para o enraizamento de cultivares de guaranazeiro (paullinia cupana, var. sorbilis, (mart.) ducke)

Abstract

Although guarana (Paullinia cupana var. Sorbilis (Mart.) Ducke) is a culture of great interest to the Amazon region, its productivity is still low. The availability of plant material that is genetically uniform, precocious and productive is the key for expanding and improving the culture in the region. To achieve this, it is recommended to do vegetative propagation, although some cultivars have rooting problems. This study aimed to evaluate the rooting of guarana from fertilized and unfertilized plants submitted to increasing levels of irradiance, with and without application of IBA. It also aimed to correlate the reserves of the branches and cuttings with rooting characteristics. The design was completely randomized in factorial arrangement of 6x4x2x2. The factors studied were the following: (i) five cultivars and one genotype of guarana, (ii) four levels of irradiance, (iii) with and without fertilization and (iv) application of IBA or not. The experimental unit contained 10 cuttings with four repetitions. The mother plants received or did not received fertilizer in the field for ten years and were subjected to increasing levels of irradiance for 60 days. The cuttings were taken from these plants and remained in the nursery for 120 days for rooting. After this period we evaluated the number of rooted cuttings with calluses and dead, root number, volume, length and dry weight of roots. The carbohydrate content was determined from the branches and rooted cuttings at the time of the dismantling of the research. The rooting of cuttings was higher for the fertilization treatment for BRS-Maues, CMU-CG 381 and BRS 882. The reduction of irradiance on the mother plant favored rooting. The highest percentage of rooting and lower mortality were obtained from cuttings without IBA treatment, independently of cultivar. The cv. BRS-Maués showed the highest rooting potential, while BRS-CG882 had the lowest rooting. BRS-Maués was more efficient in accumulating starch than the BRS- 882 CG and the rooting potential of both cultivars was positively correlated with the starch accumulated in each one. Regarding the total soluble sugars in the branches, there was no correlation for BRS-882 CG. For BRS-Maués the correlation was negative in relation to rooting of these twocultivars.