Enzyme structure and mechanism (2nd edn): by Alan Fersht, W. H. Freeman & Co., 1985. £14.95 pbk, £28.95 hbk (xxi + 475 pages) ISBN 0 7167 1615 1

Abstract

Research was carried out on butternut squash cultivar “Waltham F1”, following the organic agriculture practice, in order to evaluate the effects of two production systems (open field and greenhouse) and four transplanting times (16 April, 30 April, 14 May, 28 May in the open field; 2 April, 16 April, 30 April, 14 May in the greenhouse) on growth, productivity and fruit quality indicators at harvest and during an eight months storage of fruits. Yield, number and mean weight of fruits showed a better performance in greenhouse than in open field crops. The highest yields were recorded with the second and the third transplanting time. Greenhouse crops produced fruits with higher values of dry weight, sucrose, total proteins and ascorbate, whereas the open field cultivation produced fruits with better values of glucose, fructose, total acidity, ash, colour and carotenoids content. Most quality indicators increased from the first to the fourth transplanting; starch, total proteins and ascorbate did not vary. The open field crops produced fruits with higher content of calcium, potassium, copper and iron, but lower nitrates compared with the greenhouse cultivation. The fruit mineral content decreased from the earliest to the latest transplanting time, with the only exception of calcium, which increased. During the eight months storage a complex evolution pattern was recorded: dry matter and starch content in the fruits decreased; glucose and fructose increased; soluble solids, sucrose, acidity, total proteins, ash and colour showed an initial increase followed by a later decrease; the mineral composition did not change with time.The greenhouse system proved to be more effective than the open field management in terms of yield and, to a certain extent, of fruit quality. The intermediate transplanting performed in the second half of April in greenhouse, and in the first half of May in the open field, gave the nearest match in yield and fruit quality.