Abstract
Plants exist as integrations of their many parts and processes. Each part is conditioned by a distinct collection of genes that interact and integrate with the genes that condition other plant parts or processes (44). Root characteristics are conditioned by about 30% of the plant genome, and one-third of these (10% of the total) condition only root characteristics (39). This level of control for a single plant organ is in agreement with that of other plant organs (25) and implies that root characteristics are as amenable to genetic manipulation as the characteristics of any other plant organ or tissue. Root characteristics are not normally emphasized in plant breeding programs because of the difficulty in observing them in situ, rather than because of a reduced potential for improvement. The level of genetic control described (39) should allow the development of isogenic root mutants that have modified physiological and developmental controls to be used for precise experimentation. Data derived from experimentation with these isogenic root mutants would provide a sound basis for developing and testing hypotheses leading, ultimately, to genetic improvement of vegetable root systems.
Abstract
Mycorrhiza refers to a mutualistic, symbiotic relationship formed between fungi (Gr. mukes) and living roots (Gr. rhiza) of higher plants. These associations are prevalent among most plant species and have been observed in most vegetables except the Cruciferae and Chenopodiaceae. In fact, some vegetables do not appear to grow or develop normally without mycorrhizae. In addition to their wide distribution in the plant kingdom, these nonpathogenic relationships are geographically ubiquitous. Thus, the mycorrhizal condition is the rule, as both host plant and fungus specificity is minimal and usually not observed.
Abstract
If wastewater is to be recycled safely for agricultural production the problems associated with using it on vegetables need to be known. The objective of this review is to determine those problems. Several earlier reviews dealing with the use of wastewater in agriculture have been published (5, 7, 9, 19, 27, 30, 31, 42). Raw wastewater, or primary effluent, is not considered in this paper because secondary effluent is the type of wastewater generally used for irrigation in the United States (42). Primary treatment involves only settling tanks, from which anything in the raw sewage that can float or sink is removed. Sewage from primary treatment is subjected in secondary treatment to the action of living microorganisms: e.g., activated-sludge processes, trickling filters, treatment ponds (42). Also, this paper is limited in discussion to municipal waste-water and does not mention wastewater from industry, including wastewater from vegetable-processing plants. This review is divided into 3 areas: physical, chemical, and biological problems.
58 ORAL SESSION 18 (Abstr. 124-131) Vegetables: Stress
Abstract
There are, no doubt, hundreds of measurements that might reflect quality when all perspectives are considered (growers, shippers, processors, retailers, consumers). Many of the “things” measured will be affected to a greater or lesser extent by manipulating the nutrient environment and there are approximately fifteen essential elements alone to manipulate.
Polyculture mixtures of several species of cover crops may be the best way to optimize some of the benefits associated with cover crop use. In the first year of a three year study, 16 polyculture mixtures of cover crops (4 species/mixture) were screened at seven sites throughout the state. Five of the mixtures were seeded at two planting dates. Fall evaluation of the cover crop mixtures included ease of establishment, vigor, percent groundcover, plant height, and relative biomass. The two mixtures with the highest percent groundcover were (1): sudex, rye, mammoth red clover, and subterranean clover (62% and 80% groundcover, one and two months after planting respectively), and, (2), annual alfalfa, hairy vetch, ryegrass, and rye (56% and 84% groundcover one and two months after planting respectively). The six mixtures with the highest percent groundcover did consistently well, relative to other mixtures, at all locations. Mixture (1) above also had the highest relative biomass throughout the state. Yellow and white sweet clovers, hairy vetch, winter oats, subterranean clover, red clover, rye and barley established well and maintained high vigor ratings throughout the fall. Ladino clover, timothy, and big flower vetch consistently had poor vigor ratings.
Abstract
Humans have been struggling with the plant environment since they started sowing seeds and cultivating vegetation for food. Early attempts were primarily to keep the plants alive. As time passed, trial and error showed that certain conditions favored growth and production. With this knowledge came cultural practices for each species, which were often mixtures of folklore, superstition and fact. Many of these early growing methods have been passed down to recent times.
Abstract
Considerable concern for the quality of our environment and its effects on various species of plant and animal life, and of course humans, has been recently expressed. One specific aspect of this concern is the possibility that vegetable products may contain large amounts of nitrate. The implication made is that increased use of nitrogenous fertilizers must always result in an increased nitrate concn in the plant product (4). This is not necessarily the case, since a great number of factors govern nitrate accumulation in plants.
Three cropping sequences and three tillage systems were evaluated for increasing returns on small farms under reduced tillage. The sequences were spring 'Packman' broccoli followed by 'Sunny' tomatoes, spring broccoli/tomatoes/fall broccoli, and tomatoes/fall broccoli. Each sequence was grown conventionally tilled with no winter cover, conventionally tilled with a wheat winter cover and no-till transplanted directly into killed wheat. The study was conducted at Knoxville, TN (elev. 251m, Greeneville, TN (elev. 400m) and Crossville, TN (elev. 549m) during 1989 and 1990. Experiments were arranged in a strip plot design with sequences stripped across tillage treatments. No. 1 tomato yield was reduced in no-till at Greeneville (1989). Percentage of No. 1 tomatoes was not affected by tillage but the tomato-broccoli system produced a greater percentage at Greeneville (1990). Percentage of cull fruit was greater in Knoxville (1990) for conventional/no cover. A tomato-broccoli sequence produced more cull fruit at Knoxville (1990) and Greeneville (1989). Broccoli head size and subsequent yield and value was generally greater at most environments in conventionally tilled plots. Sequence generally had little affect on broccoli production.