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  • Author or Editor: F. H. Takatori x
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Abstract

The performance of head lettuce plants (Lactuca sativa L.) from normal seedlings and from those exhibiting slight and severe expressions of physiological necrosis (red cotyledon) were evaluated throughout growth to vegetative maturity. Plants from necrotic seedlings were delayed 1 to 2 weeks in formation of new leaves, accumulation of leaf area, and in vegetative maturity compared to plants from normal seedlings. At natural vegetative maturity, however, leaf number and area were comparable among plants of all treatments. Normal seedlings produced solid heads at maturity. Heads formed from slightly necrotic seedlings ranged from solid heads, to a loose folding of leaves over the growing terminal, to an open rosette of leaves classed as nonheading. Severely necrotic seedlings consistently produced heads of the latter 2 types, neither of which was considered of commercial quality. A reduction in or absence of the tap root appeared to strongly restrict vegetative head development. There was a direct relationship between condition of the root classes as tap root prominent, short or absent, and the quality of the head, characterized as solid, loose or open (nonheading), respectively.

Open Access

Abstract

The effects of soil moisture deficit on yield and quality of head lettuce seed (Lactuca sativa L.) were studied. Three moisture levels (−0.3, −0.8 and −5.0 bars) were imposed upon lettuce plants continuously or in various combinations during vegetative and reproductive growth. Highest seed yields were obtained from treatments of intermediate water deficit during vegetative growth. Severe stress significantly reduced seed yields when introduced during either vegetative or reproductive growth. These treatments resulted in the lowest average number of seeds/seed head and seed heads/plant. Average seed weights were highest from plants exposed to severe stress for extended periods. Lowest average seed weights were produced on plants grown in adequate moisture treatments. Seed length, width, thickness and volume correlated with seed weight in response to soil moisture deficits. Germination was high in all treatments (97-100%). The lowest percentage abnormal seedlings observed during germination were obtained from seed developed on plants in severe and intermediate water deficit treatments. Seeds from these same treatments also produced the most vigorous seedlings, based on radicle length. Moisture levels conducive to highest seed yield generally produced lower quality seeds. Intermediate water deficits during vegetative and reproductive growth of lettuce plants appear to produce highest seed yields together with adequate seed quality.

Open Access

Abstract

In propagating Asparagus officinalis L. through the method of shoot apex culture, apices of terminal buds of spears produced in vitro were found to be equally satisfactory as explants as those of lateral buds of spears obtained from the field. A maximum number of plants was obtained when the cultures were illuminated 4-20 hr daily with white fluorescent or Gro-Lux lamps at an intensity of 1000 lux. A constant 27°C temp was also optimum for plant formation in vitro. Histological examination revealed that roots arose adventitiously from callus which formed at the base of the explant, whereas spears originated from axillary buds.

Successful transfer of plants from laboratory to soil required a prior reculture in a medium lacking NAA and with the light intensity increased to 3000 or 10,000 lux. Examination of the chromosome numbers of plants propagated through shoot apex culture showed that the original diploid status had been retained in every plant.

Open Access

Abstract

A nutrient medium which enabled rapid formation of new spears and roots in shoot apices excised from buds as well as lateral branches of Asparagus officinalis L. spears was developed. This medium was composed of the following, in mg/1 : Murashige and Skoog’s inorganic salts; NAA, 0.3; kinetin, 0.1; thiamin·HC1, 1.0; pyridoxin·HCl, 5.0; nicotinic acid, 5.0; myo-inositol, 100; adenine sulfate·dihydrate, 40; sucrose, 25,000; Difco Bacto malt extract, 500; NaH2PO4·H2O, 170; and Difco Bacto agar, 6000. The shoot apices were cultured under 1000 lux Gro Lux or Plant Gro light and at constant 27°C. The explants were 0.15 mm in height and composed of the apical meristem plus a few visible subjacent primordial leaves. Within 6 weeks an avg of 80-90% of the cultures developed into miniature plants with several spears and roots. These plants, however, could not be transferred to soil with much success. The transfer necessitated further culture under another set of conditions, details of which are currently under investigation. The nutrient medium was inapplicable to shoot apex cultures of A. densiflora (Kunth) Jessop cv. Meyers, A. densiflora (Kunth) Jessop cv. Sprengeri, and, A. sarmentosus (Hort.).

Open Access