Upon germination, one or more rhizomes grew from the apical end of each yellow nutsedge(Cyperus esculentusL.) tuber. Each rhizome developed a basal bulb upon exposure to light. No significant differences in germination percentages existed between four lots of tubers which differed about fivefold in weight. The weight of plant material produced correlated significantly with the fresh weight of the tuber from which it emanated. When tubers germinated three successive times, over 60% of the tuber dry weight, carbohydrate, oil, starch, and protein were consumed during the first germination; but less than 10% of these constituents were uitlized during each of the next two germinations. Plants weighed significantly more after 43 and 91 days of growth with tubers attached throughout the period than when tubers were detached after emergence.

The effect of environmental conditions on horse purslane (Trianthema portulacastrum L. # TRTPO) emergence, growth, and reproduction was studied by sowing seeds on June 10, June 30, July 20, August 10, and August 30, 1984. The first three seeding dates resulted in significantly higher seedling emergence than the August 30 date. Leaf number, leaf area, dry matter, and number of branches per plant at the peak growth stages of this weed were significantly higher for the July 20 sowing than for the other sowing dates, followed closely by the June 30 sowing. Similarly, number of nodes per plant, seeds per plant, and seed weight per plant were also significantly higher for the July 20 sowing, followed closely by the June 30 sowing. Phenological behavior of the plants indicate that: a) maximum seedling emergence takes place during June and July, b) rapid and vigorous growth occurs during July and August (rainy season) when conditions for growth are optimum, and c) production of flowers and seeds starts 20 to 30 days after sowing.

Horse purslane (Trianthema portulacastrum L. # TRTPO) seeds germinated from 20 to 45 C. Maximum germination of 90% was observed at 35 C. Germination was highest between the 4th and 8th days of incubation. Horse purslane seeds did not exhibit dormancy. Freshly harvested seeds when incubated at 35 C germinated to the extent of 54 to 56%. Seed germination steadily increased up to 7 and 8 months when stored under laboratory and field conditions, respectively. Seeds stored in soil had significantly higher germination than those stored in the laboratory. Maximum seedling emergence resulted when seeds were planted at 1 cm and gradually declined with the increased seeding depth. Seeds lying on the surface gave very poor seedling emergence.

No abstract

We sprayed yellow nutsedge (Cyperus esculentus L.) with 0.56, 1.12, and 2.24 kg/ha of (2,4-dichlorophenoxy)acetic acid (2,4-D) at the two and four-leaf stages in both field and growth chamber studies. Compared to non-treated plants, these rates significantly reduced shoot weight, rhizome weight, and rhizome number 12 days after application. There were no significant differences in these growth responses among the rates tested, when applied one, two, and three times at consecutive 12-day intervals. We pretreated two and four-leaf plants with 0.56, 1.12, and 2.24 kg/ha of 2,4-D immediately before foliar application of 14C-2,4-D. The increase in pretreatment rates decreased the percentage of the applied radioactivity which was absorbed and translocated. Of the radioactivity absorbed, a rather constant percentage translocated from the treated area in the different treatments. The radioactivity translocated from the application site for at least 288 hr after treatment. Less than 19% of the 14C-2,4-D applied was absorbed into the leaves 24 hr after application. Ninety-eight to 100% of the methanol-soluble radioactivity that translocated to developing leaves, rhizomes, and roots chromatographed identically to 14C-2,4-D.