Visiting Scientists

Claudineia Pelacani Cruz

Associated Labex Scientist Alfredo Augusto C. Alves

Physiological symptoms of aging and priming of seeds of Physalis (Solanaceae)

Research team: Claudineia Pelacani Cruz – State University of Feira de Santana-UEFS, BA; and Christina Walters – NCGRP/ARS, Fort Collins CO.

Objective: This project aims to answer the following questions: (1) The deterioration of seeds under high and low humidity may cause physiological changes similar to seeds? (2) Priming reduces seed longevity? (3) Priming in the presence of antioxidants increases the longevity of seeds? (4) The germination of seeds in the presence of antioxidants, is indicative of restoration of viability?

Approach: Seeds of 14 accessions of 7 Physalis species from Bahia (Brazil) and different US regions. Assessment to determine the best conditions for germination: 25 or 50 seeds subjected to conditions of darkness at constant temperatures of 10, 15, 20, 25, 30, 35 and 40 oC and alternate temperatures of 15-25 and 20-30 oC. Evaluations were performed daily for 25 days after sowing. The characterization of the conditions for the germination of Physalis was evaluated in relation to the critical water potential. This test was developed in two stages: first stage were used osmotic solutions of PEG 8000 prepared at concentrations of 0, 0.5, 1.0, 1.3, 1.6 and 2.0 -MPa, the second trial involved osmotic solutions of PEG 8000: 0, 0.25, 0.5, 0.75 and 1.0 -MPa. In both trials were used seeds of 13 accessions of Physalis.

Results: The results could guide the type of germination response of different accessions (native to South America and commercial lots in North America), providing some evidence of vigor, germination rate, late accessions and accessions that require more specific conditions to germinate, especially temperature. The germination of some species of Physalis is limited between 10 and 40oC, but others may germinate more slowly in these extreme temperatures. Germination between 15 and 40 oC temperatures may be used for testing thermal stress. For all accessions tested, osmotic potentials greater than -1.0 MPa prevented the germination of seeds and can be considered critical and used in future tests of stress conditions. The priming has no effect on high seed vigor, often proving to be harmful to the seeds when exposed to stresses more severe (as in osmotic solution of -1.0 and -1.2 MPa). The priming of seeds did not favor germination under sub-optimal temperature (15/25 oC), showing that although germination can occur in high variations of temperature (10-40 oC), high vigor seeds primed may show negative effects and often accelerate the death of the seeds in the initial imbibition phase. These results are still being analyzed in terms of kinetics of germination, seeking to meet a critical limit at which the speed of the process is significantly affected between different seed lots evaluated.