Number Of Strobili Research Articles

Reproductive short‐shoots of Ginkgo biloba: A quantitative analysis of the disposition of axillary structures

Ginkgo biloba, the only living representative in an otherwise extinct clade, is of pivotal importance to understanding seed plant phylogeny. Although G. biloba and its fossil relatives have been studied for over two centuries, there are both gaps and contradictions in the information available. We present data documenting the distributions of strobili and consider what an understanding of the disposition of strobili along short-shoots in Ginkgo adds to knowledge of the evolution of reproductive structures in seed plants in general. The megasporangiate strobili are found at and around the boundary between bracts and foliage leaves, while the expanse of microsporangiate strobili centers on the fifth bract back from that boundary. Quantitative analysis of the locations of the strobili along the short-shoot finds that increases in numbers of strobili are the result of recruitment of adjacent axils into morphogenetic activity. Gaps in the series of strobili are exceedingly rare. Further, while increased numbers of megasporangiate strobili arise from the symmetrical addition of axils into the fertile zone, increased numbers of microsporangiate strobili arise from a distinctly asymmetrical, basipetally biased, addition of axillary positions. This accurate morphological framework should orient molecular genetic studies that probe gymnosperm development itself or that consider gymnosperms as the proximate sources of gene expression redeployed in the origin of the angiosperm flower.

Female fertility variation in mature Pinus sylvestris clonal seed orchards

Female fertility is the basis for the output of seeds from clonal orchards and its variation is of major interest for the economics and biology of seed orchards, especially for the efficiency and diversity of seed orchard crops. Assessments of female fertility variation in 10 mature (>15 years old) seed orchards of Scots pine (Pinus sylvestris L.) were evaluated and compared. Depending on the individual orchard, fertility variation for each clone was assessed in slightly different ways, e.g. number of strobili, cones, seeds or litre of cones per ramet. Assessments in five of the orchards were made over consecutive years. The main result was that the clonal variation in mean female fertility per surviving ramet was lower than expected from the literature; the Kang–Lindgren sibling coefficient (Ψ) within individual years averaged 1.35. The variation between ramets within clones and years was of similar magnitude as that between clones. Clone by year interactions were noticeable, but were slightly lower than the variation between as well as that within clones in individual years. There was considerable variation in the variance components between years. The limited variation in female fertility indicated that it should not be a selection criterion when selecting clones for a seed orchard. Furthermore, it will not result in large differences between clones in seed set or large reductions in gene diversity in productive Scots pine seed orchards.

Growth characters and number of strobili in clonal seed orchards of Pinus sylvestris

Observations were made on six grafts for each of 25 clones in three Scots pine (Pinus sylvestris) seed orchards in Turkey. The characters studied were number of female and male strobili, height below and above the longest branch, total height; diameter at base and breast height, crown diameter, and number of branches. Variation, broad-sense heritability (H2) and correlations between characters were estimated.

Fertility variation in six populations of Brutian pine (Pinus brutia Ten.) over altitudinal ranges

Fertility (number of strobili) was investigated in six natural populations over three ranges of altitudes (215–960 m) in Brutian pine (Pinus brutia Ten.) for two consecutive years. The fertility and fertility variation varied among populations and years. The average of strobilus production varied between 173 and 269 in female, and between 533 and 1,060 in male, respectively. The fertility variation did not seem closely related to the altitude, and it was not consistently dependent on the richness of strobilus production. Positive significant correlations were found between female and male strobilus production for all populations and years. Coefficient of variation in strobilus production among individual trees varied between 0.638 and 0.838 for female; and between 0.603 and 0.809 for male when flowering assessments were combined. The clone fertility variations among trees were slightly different among all six stands (sibling coefficient ranged from 1.354 to 1.525) and it is unlikely that trees in typical stands vary extremely in reproductive success.

Pollen productivity variations. Pollen-ovule ratio and sexual selection in Pinus roxburghii

Total pollen production, pollen-ovule ratio and the production of male-female strobili were recorded in Pinus roxburghii at two different altitudes during two successive years. The values of total pollen production per tree and per hectare varied between 1953.56 to 2727.16 2 10 9 and 2.91 to 4.26 2 10 14 (in 1999) at the lower altitude and 1247.5 to 1673.5 2 10 9 and 2.24 2 10 14 (in 1998) and 1599.89 to 2038.96 2 10 9 and 3.18 2 10 14 (in 1999) at the higher altitude. The pollen-ovule ratio in P. roxburghii has indicated the xenogamous type of breeding system The production of male and female cones per tree and per hectare ranged from 21.7 - 0.34 to 33.6 - 0.71 2 10 3 and 55.16 - 24.08 to 220.85 - 87.75 per tree and 32.55 to 70.56 2 10 5 and 2.76 to 26.50 2 10 3 per hectare respectively. However the production of female cones per 100 male cones oscillated between 0.25 to 0.66, which suggested the intense male competition among trees to pollinate their neighbours. A linear correlation was recorded between diameter and extent of the tree crown to the total production of strobili groups/strobili clusters, strobili, microsporophylls and pollen grains per individual tree. The ratio between the number of strobili per strobili group and the number of strobili groups per tree showed an inverse relationship; thus, the individuals with most strobili groups have the strobili groups with the least strobili and vice-versa. This ratio was also shown between the number of pollen grains per strobilus and the number of strobili per tree, as well as the number of pollen grains per strobili group and the number of strobili groups per tree.

The effects of photoperiod and temperature on gibberellin A4/7 induced strobilus production of western hemlock

Combinations of photoperiod and temperature were tested in two experiments to determine their effect during and after gibberellin A4/7 promotion of flowering in seedlings or cuttings of western hemlock (Tsugaheterophylla (Raf.) Sarg.) In the first experiment, longer photoperiods (18 h) applied during induction favoured male strobili, while hosrter photoperiods (13 h) favoured females. More strobili of both sexes were produced at 30 °C than at 20 °C. In the second experiment, treatments applied in October and November following spring induction also affected subsequent numbers of strobili produced. Darkness at 11.1 °C severely reduced strobilus production, whereas increasing photoperiods, up to the 8-h maximum tested, and lower temperature (5.6 °C), favoured expression of reproductive potential. Results indicate that temperature and photoperiod manipulations can be critical to the production of strobili in controlled environment seed orchards. Furthermore, they suggest that environmental conditions between induction and spring flush may be as important as conditions during induction for the realization of reproductive potential of western hemlock.