The possibility of using microscopic characteristics of the leaf epidermis as aids to the identification of some British agricultural grasses in the vegetative condition has been investigated.The occurrence of the following types of differentiated cells on the leaf-sheath was markedly affected by the stage of growth of the tiller: silica cells, silico-suberose couples, cork cells, asperities and incipient asperities. These cells were frequently absent or confined to the base of the sheath in vegetative tillers, but they occurred over most of the sheath in culm leaves. Silica cells tended to preponderate in young tillers and silico-suberose couples and cork cells in the reproductive stage. The inter-nerve epidermis of the leaf-blade was generally the least affected by growth stage; although less differentiated than the sheath, it was found to be the most useful location for identification purposes. Species separable on the basis of the above-mentioned characters of the leafblade were:-(a) Tall fescue (Festtica artmdinacea) from meadow fescue (F. praiensis) (b) Heath-grass (Sieglingia licciinibens) from smooth-stalked meadow grass {Poa pratensis) (c) Sheep's fescue {F. ovina), from mat-grass {Nardux stricta) wavy hair-grass {Deschampsia flexuosa) and bristle-leaved bent {Agrostis setacea). Timothy {PMeum pratense), meadow foxtail {Ahpecurtis pratensis) and bent {Agrostis spp.)were separable on the following characteristics, which were not affected by growth stage: the occurrence of crystal clusters precipitated by hot water in timothy and occasionally in meadow foxtail, but not in Agrostis species, the peculiar shape of undifferentiated cells of the nerve epidermis in Agrostis species, and the dense cover of asperities on the ligules of Agrostis spp. and Ahpevurus pratensis.
SummaryTwo cocksfoot varieties, Be 6394 and Be 6392, selected for high in vitro digestibility (IVD) were compared with S. 37 under sward conditions. The pattern of extension growth in reproductive tillers, the associated changes in N and water-soluble carbohydrates content (WSC), and IVD of individual plant organs were studied.Ten days after the mean date of head emergence, the most digestible plant organs were the leaf blades and the inflorescences; the lower internodes had the lowest IVD. At the mature hay stage the ranking was leaf blades > upper sheaths > inflorescence > lower internodes > upper internodes. At each stage N content was highest in the upper portions of the reproductive tiller, whilst the highest WSC content was found in the basal internodes.After completion of extension growth in the lower three of the five or six internodes which showed appreciable extension at flowering, there were markedly greater increments in weight per unit length in Be 6394 and Be 6392 than in S. 37. The WSC content of the stem was higher in Be 6394 and Be 6392 than in S. 37. The IVD of the lower internodes declined more rapidly in S. 37 than in Be 6394 and Be 6392.Results are discussed in relation to formulating a model for improved nutritive quality in conservation crops, and in relation to the height of harvesting such crops.
SUMMARYEarly stages in the development of reproductive tillers of S. 24 and S. 23 perennial ryegrass are described. The pattern of development of the stem apex and of the unemerged leaves present at the time of floral initiation is traced up to the time when internode extension results in the elevation of the stem apices above the level of defoliation. If tillers with stems about 10 cm long, or more, escape damage to the stem apex during defoliation, the regrowth may be expected to deteriorate rapidly in leafiness, since at this stage there are few or no unemerged leaves. Tillers with 3–4 cm stems generally bear 1–2 unemerged leaves, and hence the regrowth is more leafy.For a given stem length apical development was slightly more advanced in S. 24 than in S. 23. Consideration is given to selection methods to be used in breeding for leafy regrowths in springtime.
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