The effects of mechanically-induced stress and plant growth regulators on the growth of lettuce,cauliflower and bean (Phaseolus vulgaris L.) plants

The plant growth regulators, gibberellic acid (GA₃), ethephon and chlormequat chloride (CCC) were sprayed on young lettuce, cauliflower and bean (Phaseolus vulgaris) plants, which had either been given or not been given a mechanically-induced stress (MIS) treatment. MIS was applied by brushing the plants with paper for 1.5 minutes each day. GA₃ increased extension growth of bean and leaf length of lettuce in unbrushed plants as much as in brushed ones. CCC and ethephon were less effective at reducing the height of brushed bean plants compared to unbrushed ones. The effects of CCC on the growth of cauliflower and lettuce plants was not influenced by brushing, whereas unbrushed plants responded more readily to ethephon than did brushed ones. The effects of CCC on growth were generally similar to those of MIS whereas the effects of ethephon were in many ways different to MIS.The results are discussed in relation to the use of PGR and MIS treatments for modifying plant growth.     

The preparation in vitro of chrysanthemum for transplantation to soil

Plantlets of Dendranthema grandiflora Pennine Reel were grown from nodal sections on Sorbarods saturated with liquid medium containing 0–3 mg 1^–1 of various growth retardants. After 4 weeks they were transferred to compost and maintained at a relative humidity of 42% at 27.5°C. Wilting was assessed over a period of 3 h. Plantlets treated with paclobutrazol, flurprimidol, triapenthenol, chlorphonium chloride, uniconazol and ancymidol showed dose-related reductions in wilting up to a concentration of 3 mg 1^–1. Responses to tetcyclacis and mepiquat chloride were weaker, and no responses to chlormequat chloride, BTS 44584 or diaminozide could be detected. These observations are compatible with an hypothesis that resistance to wilting derives from inhibited synthesis of gibberellins.     

Effect of nitrogen and chlormequat chloride on the seed yield and oil content of mustard (Brassica juncea L. Czern & Coss)

The growth of mustard was increased significantly when treated with up to 80 kg N ha^–1 (N₈₀). Spraying with (2-chloroethyl) trimethylammoniumchloride (chlormequat chloride) increased seed yield and seed protein content. Spraying nitrogen fertilized plots with chlormequat chloride, increased leaf area, leaf area ratio, leaf area duration, number of siliquae plant^–1, number of seeds siliqua^–1 and length of siliqua. Reducing, non-reducing and total sugars in the leaves at 80 days after sowing were also affected significantly. Chlorophyll a, b and total chlorophyll were little affected. The number of siliquae plant^–1 was highly correlated with seed yield in both the seasons of experimentation. The correlation coefficient value () was 0.586 in 1982/83 and 0.912 in 1983/84.The total accumulation of nutrients, i.e. nitrogen, phosphorus and potassium in seed and straw was significantly affected by N₈₀ × chlormequat chloride interaction.     

The effects of lodging and a paclobutrazol — chlormequat chloride mixture on the yield and quality of oilseed rape

The effects of lodging and a plant growth regulator mixture on oilseed rape cv. Ariana were studied in three field experiments. Natural and artificially induced lodging treatments varying in time of imposition and severity were compared to a supported control. A mixture of paclobutrazol and chlormequat chloride was applied either as a spray or as paclobutrazol granules followed immediately by a chlormequat chloride spray.
In 1987, severe lodging treatments reduced yield by up to 52%. Yield penalties varied with the time at which lodging was imposed. Yield was inversely correlated with the ground cover of volunteers growing from shed seed under lodged crops.
In 1988, two experiments showed increased incidence of disease and decreases in seed yield and quality in lodged crops. Yield reductions were related to the severity of lodging. Lodging decreased oil contents and increased glucosinolate levels. PGR treatments reduced lodging and maintained yield at a level not significantly different to a supported control treatment. Oil contents were also similar in seed from PGR treated and control plots. Glucosinolate levels in PGR treated seed were similar to control levels in one experiment and intermediate to those from control and artificially lodged plots in another experiment.
The results are discussed in relation to the use of PGRs to prevent lodging in 'double zero' varieties of oilseed rape, and the potential losses from using ground vehicles to apply pesticides after flowering.     

Modification of seedling growth of triticale and barley by seed-applied chlormequat

Seeds of triticale and barley were soaked in a range of dilutions of chlormequat. Germination was monitored and the growth of seedlings assessed for up to five weeks. Some concentrations of chlormequat produced seedlings with significantly more leaves on the main stem, more primary tillers, a greater leaf lamina area and a higher shoot dry weight. It is argued that these modifications could lead to an increased yield potential.     

Growth regulator effects on storage root development in carrot

The major carbohydrates stored in carrots are sucrose, glucose and fructose. The ratio of sucrose to reducing sugars varies between cultivars, with early forcing types generally having a higher level of reducing sugars while storage types have a greater proportion of sucrose.In an early forcing cultivar, Super Sprite, high acid invertase activity was correlated with low levels of stored sucrose. As acid invertase activity decreased, the levels of reducing and non-reducing sugars appeared to be related to a balance between alkaline invertase and sucrose synthetase activities.Foliar applications of gibberellic acid at 35 and 42 days after sowing reduced the root/shoot ratio while similar applications of chlormequat chloride marginally increased the ratio. Both growth regulators temporarily increased sucrose stograge, but only gibberellic acid consistently reduced hexose accumulation.Gibberellic acid reduced acid invertase activity following both applications while only reducing the activities of sucrose synthetase after the first application and alkaline invertase after the second application, respectively. Chloremequat chloride increased acid invertase activity after the first application but otherwise has no effect on the activities of the enzymes studied. The significance of changes in assimilate partitioning are discussed in relation to published schemes on carbohydrate storage in root vegetables.     

No effect of the plant growth regulator, chlormequat, on boar fertility

Chlormequat is a commonly used plant growth regulator in agriculture. Defined levels of chlormequat residue are allowed in food and an acceptable daily intake is defined for humans. However, there are results in the literature suggesting that a daily intake below the acceptable level for human is detrimental for mammalian reproduction. In the present experiment we investigated the effect of chlormequat at levels up to that acceptable for humans on reproduction in male pigs. Chlormequat (also known as chlorocholine chloride (CCC)) was mixed into the diet and given to the experimental animals at three levels (three treatment groups), i.e. 0 mg CCC/kg BW per day (Control), 0.025 mg CCC/kg BW per day and 0.05 mg CCC/kg BW per day. Eight mother sows per treatment group were used in the experiment. From the day of insemination, the mother sows received the experimental diets. The piglets were weaned at 4 weeks of age and two boar littermates continued on the same treatment as the dam until maturity and delivery of semen for in vitro fertilization (IVF) and in vivo fertilization. Semen volume, sperm concentration and fraction of live sperms were not (P 0.46) detrimentally affected by chlormequat intake. The fraction of oocytes developing to more than the one-cell stage at day 5 after IVF was not (P = 0.88) detrimentally affected by chlormequat intake. Chlormequat intake did not detrimentally affect the fraction of gilts being pregnant after one insemination (P = 0.65) or the number of embryos in the pregnant gilts (P = 0.36). Serum chlormequat concentration was 0.9 μg/kg in the 0.025 mg CCC/kg BW per day group and 1.8 μg/kg in the 0.05 mg CCC/kg BW per day group, but was below the detection limit in control animals. In conclusion, the plant growth regulator chlormequat could not be proven to be detrimental to the selected reproduction traits in male pigs. This is in contrast to existing results from the male mouse.     

Effect of tetcyclacis and chlormequat applied to seed on seedling growth of triticale cv. Lasko

The growth of triticale seedlings from seeds treated with three concentrations of the plant growth regulators (PGRs), tetcyclacis and chlormequat, with or without drying after soaking was studied. Both tetcyclacis and chlormequat inhibited shoot growth. They reduced shoot:root ratios, first by restricting shoot growth (one week after treatment) and later by boosting root growth (eight weeks after transplanting). At the concentrations used tetcyclacis was a more active PGR than chlormequat and promoted tiller production. Drying, after soaking, promoted root growth, retarded the elongation growth of seedlings and enhanced some of the effects of the PGRs. Analyses of regressions between those growth characteristics significantly influenced by PGRs and the concentration revealed a quadratic relationship.     

Effect of growth retardants on growth and essential oil content in Japanese mint

In field experiments with Japanese mint using different growth retardants, chlormequat chloride (2-chloroethyltrimethylammonium chloride) increased the oil content significantly and inhibited growth to some extent only, whilst ethephon (2-chloroethyl phosphonic acid) at 0.06% concentration significantly decreased growth but had no significant effect on oil content. Among the two oil components studied, menthone content only was significantly increased by 0.06% ethephon whereas the other growth retardants were ineffective. Correlation studies indicated a strong negative relationship of leaf/stem ratio with plant height and herb yield while a strong positive relationship was obtained between the latter two characters. The oil content of the plant was negatively correlated with herb yield and plant height but it was related positively with leaf/stem ratio.CIMAP Communication No. 688.     

The effects of a paclobutrazol-based growth regulator on the yield, quality and ease of management of oilseed rape

A mixture of paclobutrazol and chlormequat chloride plant growth regulators (JF10405, Parlay C) was tested on field crops of two ‘double zero’ oilseed rape cultivars in two seasons. Application rate and timing of JF10405 were varied. Very large plots enabled the use of commercial farm equipment to treat and harvest the experiments. Untreated plots showed considerable lodging at harvest in all experiments. Treatment with JF10405 had only small effects on the height of mature plants but, generally, reduced lodging substantially even at the lowest rate tested. All JF10405 treatments increased seed yields, several significantly so, particularly a 2.50 litre/ha rate, although the optimum timing varied between experiments. Seed oil contents were little affected, but levels of glucosinolates were significantly decreased in some instances. Treatments giving good control of lodging also took less time to harvest, especially when cutting against the direction of the lodging. The results-are discussed in relation to the means by which these improvements in seed yield and quality were achieved, and crop management facilitated.