Correlation between the responses of leaf expansion and hypocotyl elongation to water deficit in sunflower (Heliantus annuus L.) genotypes

SATO N.; PEREYRA IRUJO, G.A; CREUS C; AGUIRREZÁBAL L.A.N

Mar del Plata

Conferencia; 18 th International Sunflower Confernece; 2012

ASAGIR - ISA

• Water stress is a major constraint to crop yields worldwide, and leaf growth is a key trait determining crop tolerance. Sunflower (Helianthus annuus L.) genotypes have been detected with contrasting response to water stress. The measurement of this response is, however, very time- and resource-consuming. The measurement of hypocotyl elongation rate is a simple method that could allow the evaluation of the response to water deficit without the need to grow adult plants. There is not any evidence, however, of a correlation between the responses at hypocotyl and leaf level. Therefore, the objective was to evaluate the relationship between the response to water deficit of leaf growth (measured in a previous work) and hypocotyl elongation in a group of nine genotypes of sunflower with contrasting leaf expansion response. • Twenty five seeds of each genotype were sown in sealed plastic boxes filled with 1 k of washed river sand and watered with 90 mL of distilled water (control) or 90 mL of 12% polyethylene glycol 6000 (PEG) (water deficit). Plants were grown in the dark at 25°C, in a controlled growth chamber, arranged in a complete randomized block design with 3 replicates in time. Hypocotyl length measurements were done using a millimeter ruler 3 days after sowing. The response of hypocotyl growth to water deficit was calculated as the ratio between hypocotyl lenght under water deficit and under control conditions, for each genotype. The response of leaf growth to water deficit was calculated (from previous data) as the ratio between final area of leaf 8 under water deficit and control conditions. Regression and correlation analyses were performed with both responses. • The response of hypocotyl growth to water deficit ranged between 31 and 58%, while that of leaf growth ranged between 50 and 63%. There was a significant positive correlation (p