Tomato plants were induced to produce fruit with abnormally large blossom-end scars (catfaces) by exposing them to 16/10C (day/night) for 2 weeks, starting at the six-leaf stage. Fruit of the second and third, but not the first, cluster showed catface symptoms. To identify the initial period of susceptibility to catfacing, `Revolution' tomatoes were greenhouse-grown for 34,48, or 62 days and induced to catface by a gibberellic acid (GA) foliar spray (43 μM) when transplanted to the field. Catfacing was significantly increased by GA sprays (23% vs. 11% of all fruit in 1989, 22% vs. 8% in 1990). There was a highly significant interaction between plant age and catfacing, with high levels for young and medium-aged, but lower levels for old GA3-treated transplants. The early-maturing `Revolution' is susceptible to catfacing from ≈25 to 60 days after sowing. Marketable yields were highest for young and medium-aged plants in 1989 and 1990, respectively. Old plants were checked in growth after being transplanted and produced lowest yields. Avoiding catfacing by using old transplants has doubtful practical value.
A series of greenhouse experiments was conducted with `Shamrock' bell pepper (Capsicum annuum L.) to gain insight into the flower abscission mechanism and to investigate methods to reduce reproductive structure abscission due to low light intensity. Foliar sprays of STS reduced stress-induced abscission. Application of the synthetic auxin NAA to the ovary substituted for pollination to effect fruit set under nonstress conditions, but did not improve fruit set compared to pollinated controls under low-light stress. Ovary treatment with GA3 and BA either alone or combined with NAA had similar results to NAA treatment alone. Foliar sprays of NAA or CPA also did not improve fruit set under low-light stress conditions. Application of NAA in an aqueous paste to the abscission zone prevented abscission but inhibited fruit growth. Taken together, the results indicate that stress-induced abscission is not prevented by auxin application to the ovary or foliage. The interaction of ethylene and auxin in reproductive structure abscission under stress conditions requires further investigation. Chemical names used: 6-benzylaminopurine (BA), p-chlorophenoxy acetic acid (CPA), gibberellic acid (GA,), silver thiosulfate (STS).
The system of using a living sod intercropped with row crops is aimed at alleviating soil compaction, a major problem for commercial vegetable producers in the United States. Monoculture screening of 30 grasses and 52 legumes was conducted to select groundcovers suitable for use as living mulches with little or no crop suppression. Five turfgrasses and 3 dwarf white clover cultivars were selected from the trial and grown between rows of sweet corn (Zea mays L.) and cabbage (Brassica oleracea var. capitata L.) in the following year. Colonial bentgrass, creeping bentgrass, and a Kentucky bluegrass/white clover mixture significantly reduced sweet corn and cabbage yields. Red fescue adversely affected sweet corn, whereas 2 American white clover cultivars caused yield reductions in cabbage. Growth of Chewing’s fescue, Kentucky bluegrass, and the wild white clover cultivar ‘Kent’ had no effect on sweet corn or cabbage yields. Correlations of living mulch dry weight to vegetable yield parameters were negative and highly significant in both experiments.
Field and greenhouse experiments were conducted to encourage growth of basal branches of tomato (Lycopersicon esculentum Mill.) through apex removal and use of plastic mulch. In the greenhouse experiment, apex removal (topping) delayed anthesis of the first flowers by 6 days, but then the faster branch growth increased flower cluster numbers more rapidly on topped plants than on untopped plants. In the first field experiment, apex removal and clear plastic mulch stimulated basal branching and led to a 25% increase in yields of the first four harvests, with the combination of treatments having additive effects. Mulching increased leaf concentrations of P, K, Ca, and NO3-N and decreased Na concentrations, whereas topping increased Ca, Mg, and Na concentrations in leaves sampled 24 days after transplanting. In 1985, mulching resulted in a 54% increase in early yields, but topping depressed marketable early yields by 20% because of fasciation (“catfacing”). In 1985, early yield of an early processing line was stimulated more by mulch than were two later-flowering fresh-market cultivars.
Two experiments were conducted on a gravelly loam soil of low N status to determine the amounts and timing of N fertilizer needed for high early and total yields of fresh-market tomatoes grown with or without clear plastic mulch. In both years, the mulch slightly increased early flower number, hastened flower production, and increased early yield. Hastening of maturity of plants on mulch resulted in a 22% increase in ripe fruit in the short (118-day) season of 1984 and a decrease in percent green fruit at final harvest. A N rate of 84 kg·ha−1 increased total yields compared to 0 N, whereas 168 kg·ha−1 of N decreased early yield in 1984 but not 1985. Applying one-half of the N at planting and sidedressing the remaining half was just as effective in increasing yields as applying all the N at planting, even with mulched plants. Low tissue NO3-N concentration (< 0.2%) 3 weeks after transplanting reflected insufficient N application for optimum yield but also resulted from limited soil moisture when applied N was adequate. The mulch has increased P consistently and, to a lesser extent, the K concentration in young tomato plants, whereas the effects of mulch on mineral concentration of other elements have varied with year, soil type, and climatic factors.
Two field experiments were conducted with two cultivars of transplanted tomatoes (Lycopersicon esculentum Mill.) with and without plastic mulch, varying the initial rate of N fertilizer, but maintaining the total N rate at 168 kg·ha–1 by sidedressing. In 1982, 0 and 112 kg·ha–1 initial N rates, and bare ground, black mulch, and clear plastic mulch were compared on a gravelly loam soil. In 1983, initial N rates used were 34, 67, 101, or 134 kg·ha–1, with bare ground and clear mulch on a silt loam soil. Effects of the plastic mulch dominated both experiments. Mulching increased rate of basal branch appearance and led to early flowering on branches. Total plant growth, as measured by vine weights at final harvest, was increased by mulch in both years. Mulching increased early yield only in 1983, but increased total yields by 13% and 79% in 1982 and 1983, respectively. Initial N fertilizer rates did not influence total yields significantly in either experiment, although high initial N rate, combined with clear plastic mulch, led to a significant decrease in percent marketable fruit in 1982. In 1983, mulching increased shoot concentrations of N, NO3-N, P, K, Ca, Mg, Cu, and Β (P = < 0.01) in spite of the fact that mulched plants were larger than unmulched plants at sampling time, 24 days after transplanting. Nitrogen fertilizer increased only the N and P concentrations and to a lesser extent than did the mulch.
Dry beans (Phaseolus vulgaris cvs. Red Kidney and Great Northern) were grown in the cool season in the lowland tropics at Los Banos, Philippines. Manual removal of flowers for 11 days from first bloom resulted in increased wt of vegetative parts and no change in rate of total dry wt gain. New branches, roots, and leaves provided efficient alternate sinks for assimilates, so that leaf area was increased and maintained longer, and more branches formed. Although temporary flower removal increased pod set compared to control plants, pod and seed abortion prevented a significant yield increase. This resulted in lower ratios of seed wt to total dry wt, and decreased pod wt production per unit leaf area.
Tomato (Lycopersicon esculentum Mill.) plants grown on polyethylene (PE) mulch in New York State frequently have more branches and increased mineral nutrient uptake and yield than plants not mulched. In four field experiments conducted on a silt loam soil, clear PE mulch stimulated root extension shortly after transplanting. One week after transplanting, roots were significantly longer for mulched than for unmulched plants in all four experiments, whereas aboveground dry matter differences did not become significant until 14 days after transplanting in two of four trials. Mulching increased branching, hastened flowering on basal branches, and increased concentration of major nutrients in the aboveground parts. In the field, stimulation of aboveground growth due to mulch might be brought about by warming of the stem by air escaping from the planting hole in the mulch. However, an experiment with black, white, or clear mulch, in which the planting hole was either left uncovered or covered with soil, showed no effect of hole closure on branching even though air temperature near the stem was increased when holes were left uncovered. The results taken together imply that the increased aboveground growth observed with mulching is a consequence of enhanced root growth and nutrient uptake.
A series of field and greenhouse experiments was conducted with three cultivars of bell pepper (Capsicum annuum L.) to determine the hormonal basis for flower bud and flower abscission as induced by low light intensity (LLI). Imposition of 80% shade for 6 days increased abscission of reproductive structures by 38% and resulted in an increase in bud ethylene production. Concomitantly, bud reducing sugars and sucrose decreased and these were negatively correlated with ethylene levels and those of its precursor, ACC. Infusion of ACC into the pedicel resulted in flower bud abscission within 48 hr. The results indicate that ethylene is the primary causal agent of pepper flower bud abscission. Production of auxin by the bud plays a role in prevention of abscission. The abscission of disbudded pedicels was prevented by infusion of NAA. Although the three cultivars had similar responses to ACC, they differed in the amount of abscission under stress, bud sugar levels, and the time of onset of ACC and ethylene production. Chemical names used: 1-aminocyclopropane-1-carboxylic acid (ACC); α-napthaleneacetic acid (NAA); (2-chloro-ethyl)phosphonic acid (ethephon).
The distribution of l4C-assimilates was examined in pot-grown ‘Redkote’ and ‘Michelite-62’ bean plants in which a lower or upper leaf was dosed with 14CO2 at flowering, pod expansion, or pod maturation. Assimilates from the leaf at node 4 moved primarily to the roots at flowering, but were translocated to actively growing pods at later stages. Dosing of the terminal trifoliate of ‘Redkote’ resulted in radiocarbon transfer exclusively to the subtending pods during pod expansion and maturation. Distribution from leaves on branches of both varieties was restricted to pods on the branch. When the main-stem node-7 leaf of ‘Michelite-62’ was dosed, 51% of the activity was recovered from node-7 axillary pods, and less from pods at nearby nodes. Thus middle and lower main-stem leaves of beans generally supply assimilates to several centers of active growth, while distribution from upper mainstem and branch leaves is more restricted.