PHYSICAL AND PHYSIOLOGICAL ATTRIBUTES OF SEEDS OF GRASS SPECIES NATIVE TO ARID MEXICO

Abstract

Establishing grass prairies in arid conditions is mainly based on propagules with low quality in specific density and low physical purity, resulting in low success. Physical and physiological traits were evaluated under laboratory conditions in propagules of Bouteloua curtipendula, Leptochloa dubia, Digitaria californica, Setaria macrostachya and Pennisetum ciliare (naturalized exotic) as control. Physical traits such as size and shape of caryopsis, physical purity of caryopsis, test weight, one-thousand seeds weight and physiological quality traits such as vigor, viability and germination were determined in two types of propagule (caryopsis and traditionally marketed propagules) at two harvest dates. Compliance with the assumptions of the analysis of variance were verified. Non-normal variables were transformed and analyzed using non-parametric Kruskall-Wallis and chi-square statistics. Data were analyzed using a conmpletely randomized design model and Tukey test (P < 0.05) for means separation. Differences (P ≤ 0.001) were found between species, harvesting dates and types of propagule for radicle and plumule length. Total viability was different between species (P = 0.046) and species × harvesting date for caryopsis and traditional propagules (P < 0.0001). No differences were found between species and harvesting dates for abnormal seedlings in caryopsis (P > 0.05). Caryopsis dimensions were different (P ≤ 0.0001) between species. At four days of testing, germination of caryopsis was 80 % in B. curtipendula. Regarding commercial propagule, L. dubia and P. ciliare reached 70 and 60% at the eighth day. Species from arid and semiarid areas have great potential for improvement of physical and physiological attributes of propagules by physical conditioning and total or partial elimination of accessory bracts, which is an important factor to improve prairies establishment in semiarid rainfed conditions by enabling mechanized planting and other benefits of quality seed.