Effects of Drought on Water Relations, Mineral Uptake, Water-soluble Carbohydrate Accumulation and Survival of Two Contrasting Populations of Cocksfoot (Dactylis glomerata L.)

The role physiological responses in survival of prolonged soilmoisture deficit was investigated in vegetative plants of twoDactylis glomerata populations: KM2 (drought-resistant) andLutetia (susceptible). The plants were grown in 1 m-deep soilcolumns in a controlled environment. After 56 d of full irrigation,water was withheld for 80 d, by which time all soil moisturehad been consumed; the plants were then rewatered for a further19 d. As drought progressed, leaf extension decreased to zero,water status declined, and water-soluble carbohydrates (WSC)at first increased and then decreased. The most pronounced differencesbetween the two populations was that all KM2 tillers survivedthe drought, but 34% of Lutetia tillers died. In comparisonwith Lutetia, KM2 was characterized by (a) slower shoot growthrate, (b) greater root density at depth, (c) maintenance ofhigher lamina relative water content, (d) greater osmotic adjustmentin leaf bases, (e) higher concentration of WSC in tiller bases,(f) greater ability to export WSC out of dying leaves, (g) lowercontent of metal ions but improved maintenance of P status,and (h) lower proline:amino acid ratio. The contribution ofthese responses to tiller survival under severe drought in controlledenvironments is contrasted with performance and persistenceof swards in the field in the harsher Mediterranean environment.Copyright1995, 1999 Academic Press Dactylis glomerata L., cocksfoot, water-stress, osmotic asjustment, drought survival, root-growth, water-soluble carbohydrates, phosphate, proline, variety comparison