Eficiência de uso de potássio e de água em genótipos de cana-de-açúcar

Abstract

Sugarcane has marked genotypic variation related to nutrient use efficiency, which in turn the approach of this subject in scientific research prioritizes studies related to nitrogen (N) and phosphorus (P), but due to the essentiality of potassium (K) as a nutrient, and its importance in the Brazilian economy, researches related to K use efficiency can help the development of efficient genotypes, which, because the K water relation functions in plants may have a direct relation in the water use efficiency. In the first experiment were evaluate the changes in morphological and physiological sugarcane genotypes (SP90-3414 and SP83-2847) promotes by the reduction of K concentration, the parameters were quantifying the leaf area; root system morphology (total length and total surface area of roots); biomass of roots and shoots; K concentration and accumulation in plant tissues; total soluble and reduced sugars percentage; activity of the enzyme nitrate reductase; leaf water potential and gas exchange parameters. The K concentrations used in the nutrient solution were 1 and 6 mmol L-1 , distributed as experimental design of randomized complete block design, using a factorial 2 x 2 (two K rates x two sugarcane genotypes), with five replications. The rates caused differences in the K uptake efficiency by cultivars, triggering positive changes in their accumulation in plant tissues and the morphological and physiological parameters. The second experiment were to evaluated the influence of water deficit on morphological and physiological parameters of the plants and to study the behavior of these parameters according to the increase of the available K concentration. The analysis aimed to evaluate the water relations in plants and the water status interference in the gas exchange process, as well as relating the parameters of the K use efficiency with the efficiency of water use. The experiment was conducted in pots containing 8 dm 3 of soil, the experiment was also conducted in a randomized block design, using a factorial 2 x 2 x 2 (two K rates x two water regimes x two sugarcane cultivars), and the K rates used was 1 and 6 mmol c dm-3 of soil, water regimes was 70% and 20% of field capacity and the genotypes were the same as the first experiment. The results shows improvements in water and gas exchange parameters of cultivars developed in high-level K and subjected to water deficit, showing a positive relationship between potassium fertilization and sugarcane plant resistance to adverse water condition. On average, the highest water use efficiency (WUE) of SP83-2847 tolerant genotype may result from potassium use ufficiency (KUtE).

Respostas fisiológicas da cana-de-açúcar com suplementação potássica em dois regimes hídricos

“…**, * e †: significativo ao nível de significância de 1; 5 e 10% respectivamente.Fonte: Autores. Na Figura 7, percebe-se que o ambiente irrigado foi superior ao sequeiro, considerando a disponibilidade hídrica da área em estudo, visto que para elevadas doses de K2O foram onde obteve-se a maior significância, o mesmo comportamento observado por (Zanchim, 2015). Resultados similares também foram encontrados por outros pesquisadores, os quais constataram a redução da condutância estomática em cana-de-açúcar sob deficiência hídrica (Pincelli & Silva, 2012;Brunelli, 2014;Geronimo, 2014), bem como a redução da condutância estomática ao longo do tempo.…”