The experiment was under a controlled environment. Tissue harvested for analysis for each species and each environmental treatment was of comparable development stage based on the attainment of full expansion of particular leaves. When plants were adequately watered, large differences in daytime atmospheric humidity had only small and inconsistent effects on dry matter digestibility and cell wall content. High temperature reduced the dry r.iatter digestibility and increased the cell wall content of recently expanded leaves of both tropical and temperate grasses. As individual leaves aged, the detrimental effect of high temperature on digestibility increased, but cell wall content was not affected. Circumstantial evidence suggests that high temperature decreased the digestibility of existing cell wall material, particularly as leaves aged. These changes may reflect an acceleration of the normal processes of tissue maturation. Leaves of comparable physiological maturity which are formed at progressively later stages of plant regrowth contain increased proportions of cell wall.
The warm-season yield of a number of subtropical Cr-pathway grasses was measured ever two seasons in small-plot trials near Kaitaia. Forage yields under dryland conditions ranged from approximately 4500 to 17 000 kgjha DM for the various grasses over the 5-month (mid November-mid April) harvest period during the trial. Setaria splendida produced high yields similar to maize or green-feed sorghum crops in the area and should be further evaluated as a specialist perennial crop. Cynodon dactylon seemed to be one of the more drought hardy grasses because it was the highest yielding during the driest period of summer. Stoloniferous Digitaria spp. and Hemarthria altissima yielded poorly during periods (January-February) when rainfall was lowest. Production of most of the grasses was lowest in late summer, with a substantial recovery during autumn, although species of Eragrostis had almost no autumn production. Chloris gayana overwintered poorly on this coastal site, but the other grasses persisted well. Irrigation increased the early summer production of all grasses, but depressed the early autumn production of some species, particularly the high-yielding grasses (S. splendida, Panicum maximum), and this is ascribed to problems of mineral-nutrient availability. The cool-season (mid April-mid November) production of these grasses and a further group of C4 and C3 species was measured during 1975. The temperate C3 species produced over 10 000 kg DMjha during the cool period, but production of the subtropical C4 species varied from 2000 to 9000 kgjha. Cool-season production of subtropical grasses was highest during spring.
Controlled-environment rooms. were used to study environmental effects on flower initiation in a range of annual forage legumes of Mediterranean origin (Trifolium, Medicago, Vicia, Lotus, Orn ithop us, and Astragalus spp.). Four treatments, one strongly inductive because of high temperatures (22/l6°c, day/night), long days (16 h), and vernalisation and each of the others lacking one of these favourable conditions, were used to test the importance of each factor in delaying floral initiation. Short photoperiods (8 h) delayed flowering by an average of greater than 35 days, but there was considerable variation among species in their level of response. Cool growth temperatures (16/l0°c day/night) had less though more consistent delaying effect, with an average of 24 days extension of flowering time. Lack of vernalisation delayed flowering least and some species showed little or no vernalisation response. Species with a weak or negligible vernalisation requirement and a short natural period of vegetative growth could flower prematurely if planted in late summer after small-grain cereal crops.
Aspergillus fumigatus, Mucor rouxii, and Sporormia minima have been isolated from the rumen contents of sheep grazing permanent pasture at Nappan, Nova Scotia. To determine the ability of these fungi to survive and grow at the low oxygen partial pressure present in the rumen, a method of determination of oxygen, nitrogen, and carbon dioxide has been developed. The lowest partial pressures of oxygen [Formula: see text] and nitrogen that could be detected were 0.0005 cm Hg and the precision of the determination was ±0.001 cm Hg. Carbon dioxide was determined with slightly less precision than achieved for oxygen and nitrogen. Using this method, respiration was detected in cultures of all the fungi named at [Formula: see text] Hg and growth was observed at [Formula: see text] Hg in the case of M. rouxii. It is concluded that all these fungi are capable of survival in the ovine rumen.
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