Growth rates of tomato seedlings and seasonal radiation.

Over 3 years 34 sowings of tomato cv. Moneymaker were made at regular intervals and the plant fresh weight was determined once or twice a week until flowering. The daily growth percentages and the number of days required for plants to develop from 0.1 to 10 g fresh weight/plant were then related to the total radiation and average daily radiation for each of the growing periods and also to data from other trials. The length of the growing period up to attainment of 10 g fresh weight/plant was determined by the amount of irradiation in winter only; from the beginning of March until after mid-September the length of the growing period remained constant. The light efficiency and also the maximum growth rate of the plants in these trials were higher than those obtained in trials by other workers. Some batches of plants grew less rapidly than others despite adequate light, but the reasons for this are not known. (Abstract retrieved from CAB Abstracts by CABI’s permission

Night temperature and number of nodes and flowering of the main stem of glasshouse cucumber (Cucumis sativus L.).

Plants of the cucumber cv. Farbio (all-female) were planted on 13 or 27 December, 10 or 24 January and grown at 3 minimum night temperatures, 12, 16 or 20 deg C from planting until 1 April. Node number/stem increased as the night temperature fell. Internodes were longer with later planting and on plants on inner rather than outer rows; these responses could not be related to light intensity alone. The number of flowers/stem was determined by the number of nodes bearing flowers and the number of flowers/node. More flowers/node occurred towards the top of the plant and late planting increased flowering at all nodes; the night temperature had little effect on numbers but these were highest at 16 deg . Earliness to flower of the first flowers/axil and the intensity of flowering both rose with temperature. Flowering was delayed only slightly by later planting. (Abstract retrieved from CAB Abstracts by CABI’s permission

Night temperature and fruiting of glasshouse cucumber (Cucumis sativus L.).

Cucumber seedlings, cv. Farbio, planted in the greenhouse on 13 or 27 December or 10 or 24 January, were grown at 21-27 deg C day temperature and 12, 16 or 20 deg night temperatures until 1 April. Later planting produced more fruit than early planting. Night temperature had only a slight effect on fruit numbers/stem, but there was an optimum near 16 deg . The rate of fruit production between 12 and 20 deg was similar, but increased slightly with later planting. Production started earlier with higher night temperature and later planting. Fruit growth was not affected markedly by night temperature and fruit weight at harvest increased with season but was not dependent on the treatments. Fruit length was also independent of night temperature or planting date. (Abstract retrieved from CAB Abstracts by CABI’s permission

Night temperature and flower abortion of glasshouse cucumber (Cucumis sativus L.).

Plants of the gynaecious cucumber cv. Farbio were planted under glass, about 30 days after sowing, on 13 and 27 December and on 10 and 24 January. Night temperatures of 12, 16 and 20 deg C were compared until 1 April, the day temperature being 21-27 deg . Only 835 of 3600 flowers aborted shortly after opening. The later planted crops showed less abortion than earlier planted ones and the lower the night temperature the higher was the level of abortion. Abortion of the second and third flowers in an axil accounted for 60% of the total, regardless of night temperature. Fruits were picked every 5 days; those with the longest hanging time (i.e. slowest growth) were found primarily in axils just below axils in which all flowers had aborted. Such fruits are known to have a reduced shelf life [see HcA 50, 7105] and quality could thus be controlled to some extent by selective thinning of fruit in these axils. (Abstract retrieved from CAB Abstracts by CABI’s permission

An attempt to analysis of the effect of light on stem elongation and flowering in Hyoscyamus niger L.

The shooting of Hyoscyamus niger was studied as a reaction to radiation with coloured or white light in various combinations of intensity and duration. Research into the reaction to very short photoperiods became possible by continuing treatments with weak light not longer than 6 or 10 days, and then to keep the plants in LD of white light until shooting.The data presented were interpreted as follows. Hyoscyamus would grow vegetatively if floral induction (an accumulative and autonomous process comprising flower bud initiation and a shooting impulse) were inhibited, also if stem elongation underlay formative inhibition (suppression of etiolation). Thus, vegetative growth may be due either to unsuitable photoperiod, primarily inhibiting floral induction, or to unsuitable light quality, primarily causing formative inhibition of stem elongation.The formative inhibition was due to the production of an inhibitor precursor, which became active principally in darkness, after a light period. In the dark, the precursor would be gradually converted into an inhibitor which itself had no measurable persistence but took immediate effect as an inhibition. In longer maintained darkness the plant was no longer inhibited, no more than during light. The inhibition by short photoperiods increased with time of radiation as in a formative light action. Near-infrared may be assumed to antagonize inhibition by inactivating the precursor