Search Results

You are looking at 1 - 7 of 7 items for

  • Author or Editor: H. Timm x
Clear All Modify Search
Authors: and

Abstract

A study was undertaken to determine a) if genotypic responses for fruit set and pollen viability in tomatoes (Lycopersicon esculentum Mill.) exposed to high temperatures are related, and b) if pollen viability at high temperature could be used to screen tomato plants for better performance in high-temperature environments. Fruit set, pollen germination, and pollen tube length varied among tomato sources exposed to 40C for 60 min, and both pollen germination (r = 0.988***) and pollen tube length (r = 0.815**) correlated positively with fruit set. Differentiation among tomato sources for increased pollen viability at high temperature was accelerated by increasing the temperature at which flowers were exposed from 40 to 48C. Pollen viability has a major role in determining the fruit set of tomatoes at high temperatures and can serve as a basis of screening for tomato plants that will potentially produce higher fruit yield in high-temperature environments.

Open Access

The influence of paclobutrazol, an inhibitor of GA synthesis, on kindertuber formation was studied using 13.5-month-old `Russet Burbank' potato (Solanum tuberosum) tubers. Suberized apical and distal tuber pieces of equal weight were sprayed daily with distilled water (control), 0.001 and 0.01 mg paclobutrazol/liter with or without 2.5 mg kinetin/liter, and 2.5 mg kinetin/liter alone. The tuber pieces were held in the dark (20C) and harvested 8, 16, and 22 days after the first treatment. Only sprouts developed from control apical piece eyes after 22 days. There was an average of 3.6 sprouts/eye, which, in total, weighed 735 mg. Sprouts (2.4/eye) from treated apical piece eyes averaged 46 mg. By 22 days, 0.001 mg paclobutrazol/liter plus kinetin applied to apical pieces resulted in the most kindertubers, 1.9/eye. The largest kindertubers (1.2 g) were produced from apical pieces treated with 0.001 mg paclobutrazol/liter. At each harvest and regardless of treatment, distal tuber pieces produced larger sprouts and more sprouts per eye than apical pieces. Kindertubers developed from distal piece eyes only with the paclobutrazol plus kinetin treatments. Distal eyes produced half as many kindertubers as apical eyes treated similarly. Apical pieces treated with kinetin alone produced fewer sprouts than control pieces, and fewer tubers than paclobutrazol-treated pieces. Sprout weight per eye of kinetin-treated apical pieces was one-third that produced by control pieces and 5.1-fold greater than that of paclobutrazol-treated pieces. A similar trend was observed with sprout weight from distal eyes. Results suggest lowered GA levels are involved in kindertuber formation on aged potato tubers, and GA content or metabolism of distal pieces is unlike that of apical pieces. Distal tuber pieces do not form kindertubers as readily as apical pieces.

Free access
Authors: and

Abstract

The effect of temperature, soil moisture, and diurnal variations in plant water content on pollen viability (PV) in bean (Phaseolus vulgaris L.) genotypes was investigated under field conditions in 1981 and 1982. Each year PV, relative water content (RWC), and leaf water potential (LWP) of each cultivar at mean soil moisture tensions (MSMT) of −0.05 and −0.10 MPa were reduced significantly between 0700 hr and 1400 hr. At a MSMT of −0.05 MPa, PV and RWC of both cultivars significantly increased between 1400 hr and 1900 hr. During the same period, the LWP of ‘California Light Red Kidney’ increased to the 0700-hr level, but remained at the 1400-hr level in ‘Gloria’. At a MSMT of −0.10 MPa, PV significantly increased in ‘Gloria’ but failed to increase in ‘California Light Red Kidney’ between 1400 hr and 1900 hr. RWC remained at the 1400-hr level in both cultivars. LWP of ‘California Light Red Kidney’ remained at the 1400-hr level, but continued to decline below the 1400-hr level in ‘Gloria’ during the same period. PV declined as both RWC and LWP decreased. A relative value for the simultaneous contribution of both high ambient temperature and the water status of bean plants to loss of PV was calculated.

Open Access

A nonenzymatic technique using dilute salt solutions effected rapid release of viable protoplasts from mature bean (Phaseolus vulgaris L.) pollen. Protoplasm release started within 30 sec and was completed within 5 min in solutions of 0.02 to 0.06 m NaCl, or KCl, pH 6 to 9. The degree of release could be altered by changing the concentrations and ratios of CaCl2 and H3BO3 and by adding sucrose to either solidified or aqueous salt media. The surface of nonenzymatically released protoplasts was partially digested by short-time exposure to a mixture of cell wall-degrading enzymes and then examined by scanning electron microscope.

Free access

Abstract

Viability of pollen grains of isogenic sibling bean (Phaseolus vulgaris L.) selections of known tolerance of sensitivity to high temperatures (HT), as previously determined by pod retention and seed yield, was compared to that of a common parent bean selection and a cowpea [Vigna unguiculata (L.) Walp.] cultivar. Exposure of newly opened flowers to temperatures of 35° or 41°C reduced the viability of pollen grains in all bean selections. Pollen of all sibling selections was less affected by HT than pollen of their common parent suggesting transgressive segregation of factors for HT tolerance. At 41°, most pollen grains were destroyed in the parent bean selection and the 2 HT-sensitive siblings, whereas 44% to 55% of the pollen grains appeared to be viable in the 2 HT-tolerant siblings. Pollen viability of the HT-tolerant cowpea cultivar was not reduced by temperatures to 41°. Pollen staining indicated an interrelationship between pollen viability and tolerance to HT stress among the bean selections. The technique described has the potential for rapid selection of HT-tolerant genotypes in hybrid populations.

Open Access

Abstract

Two bean cultivars and one breeding selection with different pod-retention characteristics were grown at mean soil moisture tension (MSMT) of 0.05 and 0.1 MPa in 2 separate plantings. In the 5 May planting, flower buds developed during the 1st 3½ weeks of flowering, were dated and counted, and those developing mature pods were identified. Sixty-five percent to 90% of all pods that reached full maturity were from floral buds that reached anthesis during the 1st 2 weeks of flowering. The percentage of pods reaching maturity varied among cultivars. About 40% of the floral buds that developed on the determinate bean selection were retained to full pod maturity. Only 20% to 25% of the floral buds developed on each of the indeterminate cultivars were retained to full pod maturity. An increase in the MSMT from 0.05 to 0.1 MPa in the 23 June planting reduced the number of pods and seeds/plant and total seed weight/plant by 20% to 40%, but the number of seeds/pod and weight/seed was not influenced by MSMT or by number of pods produced on either of the dry bean cultivars or the breeding selection.

Open Access

Abstract

Chemicals often associated with pollen function in vitro were applied under field conditions to foliage of determinate, semi-determinate, and indeterminate beans (Phaseolus vulgaris L.) to evaluate pod and seed yield response. Sprays of calcium nitrate, boric acid, ethylenediaminotetraacetic acid, detergent “Micro”, and different sugars altered pod retention and seed yield, but response varied with bean source.

Open Access