Guayule agronomics: establishment, irrigated production, and weed control

Salt effects on seed germination and seedling emergence of several crops are evaluated to understand poor plant stands occurring in furrow-irrigated fields in saline areas. The test crops were carrot (Daucus carota L. cv. Imperator 58), chile pepper (Capsicum annuum L. cv. New Mexico 6-4), tomato (Lycopersicon esculentum M. cv. Rutgers), and guayule (Parthenium argentatum G. cv. 593). Seed germination was measured in petri-dishes containing saline solutions (0.8 to 32 dSm−1 with a Na to Ca + Mg ratio of about 2 : 1); and seedling emergence in potted fine loamy sand subirrigated in a greenhouse with saline waters (0.8 to 7.6 dSm−1 with SAR < 16). Seedling emergence through a thin layer of salted-loamy sand (having ECeup to 46 dSm−1) placed on emerging seedlings was also evaluated. Germination of tomato and carrot seeds began to decline at solution salinities of 12 and 18 dSm−1, respectively, and was virtually zero at 23 dSm−1, Chile pepper and guayule germinated well at 23 dSm−1, Tomato had the highest emergence, and guayule the lowest, showing less than 20% when subirrigated at 2.2 dSm−1, Seedling emergence which increased in the order of guayule, carrot, chile pepper and tomatoes did not quantitatively correlate with seed germination. However, it did correlate with the emergence through the thin layer of the salted-sand placed over emerging seedlings except in tomato. Salinity of the saturation extract of the surface 5 mm soil increased to 21 and 31 dSm−1, in 7 days when subirrigated with water of 4.3 and 6.4 dSm−1, respectively. Poor seedling emergence of guayule, carrots and, to some extent, chile pepper appeared to be caused by hypocotyl mortality associated with the salts accumulated at the soil surface, but not by reduced seed germination. The control of surface accumulated salts should be the target of management for improved emergence of these crops.

Salt effects on germination and seedling emergence of several vegetable crops and guayule

Effect of light, gibberellic acid and abscisic acid on germination of guayule (Parthenium argentatum Gray) seed

Water quantity and quality requirements of guayule: Current assessment

Guayule (Parthenium argentatum Gray) is a rubber-producing plant native to the semi-arid region of north central Mexico and southwestern Texas. As a member of the family Asteraceae, the seed dispersal unit in guayule is comprised of an achene enclosed by two staminate florets and a bract. The seeds in this condition are dormant and need special treatment in order to germinate. Threshing, prolonged washing, and/or chemical treatments prove effective in improving the germination. Experiments showed that chaff influenced germination and seedling emergence. Bioassays of aqueous extracts of guayule chaff and the seed coat showed a significant inhibition of germination and radicle growth of guayule, lettuce, and tomato seeds. Highperformance liquid chromatography enabled the identification of at least seven phenolic acids from guayule chaff extract. These, in order of decreasing concentrations, included p-hydroxybenzoic, protocatechuic, p-coumaric, ferulic, benzoic, vanillic, and cinnamic acids. All of them are well-known germination and growth inhibitors, and seem to play an important role in the

https://www.jstor.org/stable/pdfplus/2442895.pdf

George P. Hanson

Papers

Recent Advances in Guayule Seed Germination Procedures