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Abstract

In the article “Germination and Priming of Tomato, Carrot, Onion, and Sorghum Seeds in a Range of Osmotica”, by Anthony M. Haigh and E.W.R. Barlow (J. Amer. Soc. Hort. Sci. 112:202–208, March 1987), the term “ionic strength” has been inadvertently used throughout the paper where “ionic concentration” was meant.

Open Access

Abstract

Germination responses of tomato, carrot, onion, and sorghum seeds to solutions of K2HPO4, K2HPO4 + KNO3, KNO3, K3PO4, K3PO4 + KNO3, and polyethylene glycol (PEG) 6000 at osmotic potentials between −0.25 and −1.75 MPa at 15°C were studied. Seeds that did not germinate in solutions subsequently were germinated in H2O to evaluate the efficacy of priming. Germination was more closely related to ionic strength than to osmotic potential of the imbibitional solution. Carrot seeds germinated in all salt solutions up to an ionic strength of 0.8 mol ions/liter, while onion and sorghum seeds had a threshold of about 1.0 mol ions/liter in salt solutions, except in K3PO4, which had a reduced threshold for both species. Tomato seeds, however, showed a wide range of thresholds between osmotica. The species also differed in their responses to individual osmotica. Differences in effect of osmotica for one germination parameter were not consistent for all germination parameters. Salt solution priming of tomato and carrot seeds was more beneficial to subsequent germination than PEG priming. Salt solution priming of onion seeds was less beneficial than PEG priming, while salt solutions were toxic to sorghum seeds. Tomato and carrot seeds primed in solutions that contained KNO3 had much shorter time spreads of germination than those primed in solutions without KNO3. The use of priming solutions of osmotic potential lower than that needed to inhibit germination resulted in underpriming of the seeds, which could cause a time spread of germination longer than that of untreated seeds. The presence of KNO3 in the priming solution was shown to alleviate some of the disadvantages of underpriming.

Open Access

Abstract

Conditions for priming tomato (Lycopersicon esculentum Mill.), carrot (Daucus carota L.), and onion (Allium cepa L.) seeds in solutions of K3PO4 + KNO3 and K2HPO4 + KNO3 were optimized in a series of laboratory and field experiments. When primed in K3PO4 + KNO3 (−1.6 MPa) for 7, 14, or 21 days at 15°, 20°, or 25°C, the percentage of emergence was unchanged in tomato, increased in carrot, and decreased in onion. Although there were some species differences, all priming treatments reduced time-spread and increased median rate of emergence. For this solution, priming at 15° for 14 days was optimal for all 3 species. Detailed experiments using optimized priming solutions in an aerated column for tomato (K2HPO4 + KNO3, −1.0 MPa) and for carrots (K3PO4 + KNO3, −1.5 MPa) demonstrated that 18 days was necessary to prime tomato seeds maximally by reducing the time-spread of germination from 73 to 12 hr. With carrots, the maximal response was obtained after 16 days of priming. For both species, continued gains in germination could be obtained from prolonged priming, although only at the expense of a reduced percentage of germination. Air-drying and storing of tomato and carrot seeds for up to 28 days had no effect on subsequent emergence in the field. Conversely, air-drying of onion seeds reduced the percentage of emergence and increased time-spread and rate of emergence. In contrast, salt-primed tomato seeds exhibited an increase in percentage and rate of emergence, and a decrease in time-spread of field emergence. Primed carrot seeds exhibited a faster rate of field emergence than those not primed.

Open Access

Legume ground covers were evaluated in pecan orchards to reduce nitrogen inputs and increase beneficial insects. Treatments were established at two sites in Oklahoma, each with 5 ha of a `Dixie' crimson clover/hairy vetch mixture and 5 ha of grass sod. Nitrogen was applied at 0-200 kg·ha-1 to the sod plots, but legume plots were not fertilized. Aphids and selected arthropods were monitored on ground covers and in the pecan canopies. Data indicated that a mixture of crimson clover/hairy vetch supplied up to 186 kg·ha-1 N to the trees. Beneficial arthropods monitored were Coccinellidae, Chrysopidae, Nabid, Syrphid, and spiders. Lady beetles, primarily Hippodamia and Coleomegilla, were the most important aphid predator in the spring, and green lacewing was the most important fall predator. There were fewer aphids infesting pecans using a crimson clover/hairy vetch ground cover than a grass sod.

Free access

Annual legume ground covers were evaluated in pecan (Carya illinoinensis) orchards to supply nitrogen and increase beneficial arthropods. Treatments were established at two sites, each with 5 ha of a `Dixie' crimson clover (Trifolium incarnatum) /hairy, vetch (Vicia villosa) mixture and 5 ha of grass sod. Data indicated that the legume mixture supplied over 100 kg·ha-1 N to the pecan trees. Beneficial arthropods were greater in orchards with legume ground covers than in orchards with a grass groundcover. Lady beetles and green lacewings were the most important spring predators, and green lacewings were the most important fall predator. The Species distribution on the ground covers differed from that in the canopy. Coleomegilla maculata lengi, Hippodamia convergens and Coccinella septempunctata were the most abundant lady beetle species in the legume ground covers, and Olla v-nigrum, Cycloneda munda, and Hippodamia convergens were the most abundant species in the pecan canopies. Beneficial arthropods appeared to suppress injurious pecan aphids.

Free access