Studies onxHaynaldoticum sardoum Meletti et Onnis metabolism during seed life-span: α-amylase and glutamate decarboxylase activity

Abstract

Summary. Embryo GAD activity and a-amylase in the endosperm of 2 different physiological lines (CP; CV) of xHaynaldotiCum sardoum Meletti et Onnis were evaluated and different stages of seed ripening and progressively older seeds were examined. Results concerning GAD activity during ripening show differences between CP and CV seeds, the former being more active. In the ageing seeds, the GAD remains constant (CP is twice as much as CV) up to 4th year and greatly decreases at the 5th. The a-amylase activity is fairly constant during ripening in CV endosperm and increases in CP: at the fully-ripe stage, both show similar values. During seed ageing, the activity decreases progressively in CV endosperm while, in CP, values are greater but fairly constant. The results are discussed in connection with dormancy and the different physiological ageing of seeds.xHaynaldoticum sardoum Meletti et Onnis is a spontaneous hexaploid wheat to be found in the Mediterranean area and its female and male parents are Tritieum durum and Haynaldia villosa, respectively 3. Studies conducted by Meletti 4,s have isolated 2 natural populations characterized by a solid (CP) or a hollow stern (CV) (CP and CV, in accord to Onnis4). Besides morphological and structural differences 6'7, caryopses from CP and CV populations also have the following physiological differences: CP is a winter-like wheat, with deep dormancy and a long dry afterripening; CV is a spring-like wheat, with light dormancy and a short dry after-ripening. Our previous experiments on Tritieum durum led us to study certain of the metabolic characteristics of CV and CP populations of xHaynaldoticum sardoum with the aim of correlating their different physiological behaviour with the activity of 2 enzymes, glutamic acid decarboxylase (GAD; E C 4.1.1.15) and a-amylase (E C 3.2.1.1.), involved in the energetic and degradative metabolism of germinating seed ~1~ In this way the pattern and the activity of the GAD and a-amylase during seed ripening and in the period after ripening up to the loss of germination capacity, were studied in the present paper. Materials and methods. Caryopses (seeds) from CP and CV xHaynaldotieum sardoum Meletti et Onnis at different stages (milky, mealy, doughy, waxy, fully ripe n ) were collected during the late spring and early summer of 1979. Calibrated seeds from crops from 1978, 1977, 1976, 1975, 1974 stored at laboratory conditions (18 ~ _+ 2 ~ in sealed glass containers, were also utilized. Germination assays of unripe, ripe and overly ripe seeds were carried out on water-moistened filter paper in Petri dishes, at 23 ~ in darkness. The water content (relative humidity, %) of the seeds was evaluated by means of an Ultrax hygrometric balance. All the seeds were sterilized for 5 min with 1% Relative humidity, respiratory activity and germination capacity of CP and CV ripening seeds. Seedling growth, at the 10th day, of fully ripe seeds NaC10 solution and their embryos or endosperms were isolated by means of a sharp gauge and utilized as an enzymatic so...