Experiments are described in which the relative importance of head storage capacity and carbohydrate supply was examined in five sorghum varieties of different heights. The varieties were: Namatera (270 cm), Dobbs (180 cm), MUS 78 (100 cm), MUS 23 (85 cm) and MUS 70 (85 cm). Techniques used were (i) cutting off part of the head or part of the leaf at anthesis, (ii) shading during different periods of development, and (iii) thinning the plants at different physiological stages. Varietal differences ranged from a situation where the head was little more than half-filled by the available carbohydrate (MUS 78), through intermediate stages (Dobbs and Namatera), to a situation where the head capacity limited the amount of carbohydrate which could be stored (MUS 23 and MUS 70). Some differences could be attributed to pre-anthesis competition between head and stem, but in the dwarfs a more important factor appeared to be pre-anthesis competition between head and leaf. It is suggested that for maximum efficiency of grain-yield production, maximum carbohydrate should be utilized for pre-anthesis head and leaf growth and that partitioning between these plant parts should be such that the supply of carbohydrate for grain filling is in balance with head storage capacity.

Observations made on freezing tissue show that the appearance of extracellular freezing can occur in tissues which have been initially frozen intracellularly. Since the evidence for the assumption that intracellular freezing is of rare occurrence in the field is based on the microscopical observation of ‘naturally’ frozen tissue it can no longer be assumed that this process is unconnected with the survival of plants overwintering in the field.

Magnesium deficiencies have occurred on most crops grown on sandy soil of the Cottenham Series at Woburn (Bolton & Penny, 1968). This paper gives the results of an experiment on this soil comparing the relative effects of dolomite (MgCO3. CaCO3), Epsom salt (MgSO4. 7H2O) with and without limestone (CaCO8), and calcined magnesite (MgO) on the yields and composition of sugar beet, potatoes and spring wheat grown in successive years. Effects on soil composition are also given.

Honeybees were able to distinguish between the flowers of two different oultivars of kale grown to produce hybrid seed and most foraged only on one or other of them.