Inflorescence Characters Research Articles

Environmental and genetic effects upon reproductive growth in tall fescue (Festuca arundinaceaSchreb.)

SUMMARYThe environmental and genetic control of reproductive growth was studied in S. 170 a variety ofFestuca arundinaceaSchreb. The variety had induction requirements for short days and low temperatures before inflorescence production could occur, but some genotypes became induced with only short-day treatments. Low temperatures and short days in controlled environment rooms were less effective in bringing about induction than winter conditions in an unheated glasshouse. Only non-additive genetic effects could be shown to be significant in the control of induction requirements. Field studies showed that all inflorescence characters were subject to genetic and genetic x environmental control, and they also indicated that seed weight per inflorescence and seed fertility were most likely to show a response to selection. Diallel analysis under glasshouse conditions showed that the seed fertility and 1000 seed weight of the parental crosses were subject to maternal control, but these effects were not detectable in the next generation. Genetic control of seed fertility and 1000 seed weight in the diallel progeny was mainly additive.

TAXONOMIC AND MORPHOLOGICAL NOTES ON CLARISIA (MORAC.)

Studies in the Moraceae showed that Acanthinophyllum should be regarded as congeneric with Clarisia, and that Clarisia spruceana and Aliteria sagoti are conspecific with Clarisia ilicifolia. Some characters of the inflorescences and seeds and the position of Clarisia and its relationships with Trophis and Sorocea are discussed.

Intraplant Morphological Variations in Grasses

Clonal progenies were developed from individual nodal segments of bromegrass, cormlets of timothy, and secondary basal buds of sorghum. The parent plants were morphologically unstable or chimeral and occurred in either hybrid or inbred populations. Intraplant clonal progenies usually continued to be unstable through the second clonal generation. Marked deviating types occurred within clonal rows. Intraplant comparisons were made of inflorescence characters and seed-set following open-pollination of unstable plants from inbred lines of smooth bromegrass. Significant differences occurred between characters in panicles from different parts of the same plant.

INTRAPLANT MORPHOLOGICAL VARIATIONS IN GRASSES

Clonal progenies were developed from individual nodal segments of bromegrass, cormlets of timothy, and secondary basal buds of sorghum. The parent plants were morphologically unstable or chimeral and occurred in either hybrid or inbred populations. Intraplant clonal progenies usually continued to be unstable through the second clonal generation. Marked deviating types occurred within clonal rows. Intraplant comparisons were made of inflorescence characters and seed‐set following open‐pollination of unstable plants from inbred lines of smooth bromegrass. Significant differences occurred between characters in panicles from different parts of the same plant.

Some Additional Remarks on Inflorescence Characters in the Commelinaceae

In connection with L. L. Forman's article on A'theolirion Forman in Kew Bull. 16: 209-221 (1962) I had the opportunity to give some clarifying notes on Briickner's 'Doppelwickel' and Woodson's 'individual' and 'paired cymes' (Kew Bull. 17: 315-316 (1963)). I am grateful to Forman that, by his postscript and by a kind personal letter, he has drawn my attention to some still existing uncertainty as to my own position concerning inflorescence characters in the Commelinaceae. For the sake of brevity I have used the term '2-sided cincinni' relying on the reader to remember Woodson's own words in Ann. Miss. Bot. Gard. 29: 143 (1942): 'In ... the Tradescantieae . . . the ultimate branches or units of the inflorescence are paired sessile scorpioid cymes which appear as a 2-sided unit superficially... "parted in the middle" ...'

The North American Mesquites Prosopis Sect. Algarobia (Leguminosae)

Bentham (1875) included nearly all the plants of Prosopis Sect. Algarobia DC. emend. Burk. (Leguminosae) in one polymorphic species, P. juliflora (Sw.) DC., distributed from Chile and Argentina to the United States. His treatment has been followed by most North American authors, e.g. Sargent (1902). Most of these authors have recognized in the United States the varieties glandulosa (Torr.) Coekerell and velutina (Woot.) Sarg. The discovery of an older name, P. chilensis (Mol.) Stuntz, based on Chilean plants, was followed by nomenclatural transfers of these varieties. In the same section, Burkart (1940) can recognize a number of species, among others P. chilensis sens. str., P. jutliflora sens. str., P. articutlata S. Wats., P. glandulosa Torr. and P. velutina Woot. That members of this section have indistinct morphic boundaries is probably due, says Burkart, to hybridization. Burkart cited, and presumably saw, rather few North American collections. Benson (1941) agrees that P. chilensis is not conspecific with the North American mesquites, but can recognize only one species in the United States, P. juliflora, with three varieties, glandulosa, veluttina, and torreyana. The oftenremarked taxonomic difficultv of this section needs no further emphasis than to point out these divergences in treatment. Field and herbarium studies of mesquites have been undertaken to determine whether considerable discontinuities exist between populations of mesquites, and whether combinations of certain characters show geographic localization. Some recent work of this nature has been done by Graham (1960) in northeastern Mexico. Graham demonstrates the existence of a narrow contact zone or zone of morphic inter(gradation between the lonI-leaved P. glanidulosa and a kind of "short-leaf" mesquite (included in P. laevigata in this paper). The characters which Graham finds to be siQmifieant are quanititative foliage characters. Benson (1941) distincuished the mesquites of the United States mainly on the basis of quantitative foliage characters. Preliminary studies on all the members of this section likewise indicate that foliage characters are geographically segregated and are of prime taxonomic value. Characters of fully mature fruits are also geomraphically segregated, and well correlated with those of foliage, but such fruits are so infrequently present in the field or on herbarium specimens that their taxonomic value is secondary. Quantitative inflorescence characters, such as absolute length of raceme, or raceme-length relative to leaf-length, may prove to be distinctive, but their evaluation is difficult. Quantitative characters of the flowers are very difficult to evaluate because of the proterogynous development (Burkart 1940) ; measurements have to be taken at comparable stages of developmnent, since the genitalia differ so greatlv in relation. to each other at different stages. The geography of some of the quantitative foliage characters is presented on the nmap, Fig. 2. The data were taken from herbariuim sheets. They do not

Developmental morphology of the floral organs of Eucalyptus. I. The inflorescence

The nature and structure of the inflorescenoe of Eucalyptus is re-defined in the light of an analysis of the unit inflorescenoe, its development, mode of branching, bract systems, and the grouping of unit inflorescences into compound inflorescences. The structure of the unit inflorescence in 80 representative species is elucidated and a systematic notation for expressing the numbers and arrangement of the involucral bracts in dichasial inflorescences is proposed. The infloresoence bud of Eucalyptus is generally asymmetrical in side view and often also in face view. External asymmetry is largely a result of the asymmetry of the outermost pair of bracts, by which the developing inner bracts and flowers are at first tightly enclosed, and may be reflected in an asymmetrical pattern of branching within the inflorescence. The asymmetry and pattern of branching are reflections of morphological features peculiar to the shoot system of Eucalyptus. The outer bracts resemble the adult leaves in their asymmetry about the midrib. The leaf and bract primordia arise decussately at the shoot apex but in most species the leaves of each pair become separated by the development of a segment of axis (an "intranode") between them. In certain species the development of an intranode between the outer pair of bracts leads to the splitting apart or "disarticulation" of the unit inflorescence into two subclusters. The very complex inflorescence of E. camaldulensis arises by disarticulation of a simple inflorescence, followed by interpolation, in a centripetal manner, of additional bracts and flowers between those first formed. Flower numbers in clusters at successive nodes of the annual shoot may vary, rising with node number if the inflorescences are basitonically disposed, falling if acrotonically disposed. Flower number in successive clusters is correlated with other quantitative features of the annual shoot. The position and number of the inflorescenoe buds on the annual shoot and the interval between flower initiation and anthesis are characteristic of species and of groups of species. Phylogenetic trends in inflorescence characters are discussed. Inflorescences with few flowers and with free persistent bracts, the number of which is related to the flower number in the cluster, are held to be primitive. Inflorescences with many flowers, fused bracts constituting a caducous involucre in which the number of bracts is not related to the number of flowers, are held to be advanced. These and other charaoters of the infloresoence are shown to have taxonomic significance and their use is typified in an analysis of the infloresoence characters of the Renantheroideae in relation to those of the Renantherae.

Origin of Citrus fruits with reference to Himalaya region

If the occurrence of Citrus ichangensis (Ch'eng chou chih _??_) in Naga Hills, Assam, is to be justified, the East Himalayan foothill region should in-volve every representative of Citrus subgenera and sections except the monotypic Citrus madurensis (Chin chu _??_) of the section PSEUDOFORTUNELLA of possible garden origin. It's presumable that the origin of the genus Citrus is quite analog-ous to the creation of unifoliolate and solitary-flow-ered Citropsis Tanakae from other pinnate (or tri-foliolate) and paniculate (or racemose) members of the genus in the comparatively cooler region of Africa, and that of northernmost Severinia buxifolia (Kou chu _??_) of similar status from tropical mem-bers of the same genus having distinct inflores-cence. In such circumstances, some agency must have been existed in Eastern Asia several thousand years ago to drop the characters of compound leaf and inflorescence, leaving possible remainder represented by Poncirus trifoliata (Ju chou chih _??_) in the Yangtze valley of interior China. The origin of the subgenus METACITRUS, therefore, must have happened at the stage when paniculate subgenus ARCHICITRUS lost the inflorescence, as in the case of Citrus ichangensis from the section PAPEDA, like Citrus latipes, C. Combara of Eastern Himalaya. From the fact that the PAPEDA group and the section OSMOCITRUS occupy the broadest area of Citrus distribution, a considerable period must have elasped while the genus is represented only by these two sections of plants, undoubtedly giving rise to its start from Assam and its adjacent territory. Although sect. ACRUMEN approaches most to OSMOCITRUS and both territories of Assam and the Yangtze Valley have definite representatives like Citrus indica and Chu _??_ (still unnamed), its repeated sporadic occurrences throughout the Pacifi ter-ritories may prove its very late origin, somewhat earlier than that of the genus Fortunella, without the direct link to OSMOCITRUS. After PAPEDA had become perfectly adapted to the tropical climate, it must have found the way to transform into the Contribution No. 6, from Tanaka Institute of Cit-riculture and Horticultual Science, College of Agriculture. University or Osaka Prefecture lime (sect. LIMONELLUS) and the shaddock (sect. CEPHALOCITRUS) by either thinning or thicken-ing of pericarp and a considerable elongation of pulp vesicles with the change of contents (the loss of acrid oil). This evolution must have occurred during their southward move to the Pacific Ocean from Himalaya, as evidenced by the fact that the former still grows wild in Malay Peninsula and the latter penetrates deep into East Himalayan foothills and interior China, recorded by men at least 2500 years ago. In the next stage, the transformation of LIMONELLUS must have been directed toward the gain of strong citral aroma without the change of rind texture, intensified anthocyanin pigmentation and the fruit elongation, together with the complete loss of petiole wing. This brought out the small citron (Citrus limonimedica) and the lemon (C. Limon), representing sect. CITROPHORUM, and in taking mainly westward advancing route along the Himalaya range, it gave birth to the sweet lime (C. limettioides), Galgal (C. pseudolimon, n. sp.), Galgal Large (C. macrolimon, n. sp.), etc., but it left very important footprint in Assam in the form of closely related Citrus Limonia and C. Jambhiri. Undoubtedly both sour and sweet oranges (sect. AURANTIUM) are the direct descendants of the shaddock, having secure natural habitat in Assam, and posessing stabilized globose fruit with a great advancement of carotenoid pigmentation

INFLORESCENCE TYPES OF STRAWBERRY VARIETIES

In any attempt to increase production through breeding it is obviously important to recognize the characteristics that determine the differences in productiveness of the varieties of any crop. When recognized, these characteristics may be used as guides in breeding, in the selection of seedlings, and in a study of the effect of external conditions on the plant. Among the more important characteristics now recognized which affect the productiveness of strawberry varieties are season and conditions of fruit-bud formation, length of bearing season, frost resistance of flowers, disease resistance, hardiness of plants, sterility of the flowers, number of fruits per inflorescence, number of inflorescences per plant, and size of fruits. Sterility of the flowers of hermaphrodite varieties has recently received attention (I, 2). It has been shown that some varieties produce few sterile flowers whereas others produce flowers most of which are sterile. The percentage of fertile flowers produced by any one variety varies with soil and seasonal conditions. In the case of the Ettersburg 121 variety in Oregon, Schuster (8) has given striking proof of the relation of fertility to the soil type on which it is grown. On nearly all the heavy soils in that state it is one of the most productive sorts, but on lighter soils this variety is so sterile as to be unprofitable. On sandy soils in Maryland less than i percent of the flowers of this variety set. Valleau (g) has called attention to the definite relationship between flower position and sterility in the hermaphrodite varieties. Recently this has been emphasized and extensive records on the behavior of varieties in this respect have been published (i). It was found that the primary flower of an inflorescence is more likely to prove fertile than are later flowers, while the secondary, tertiary, quaternary, and quinary flowers, respectively, are less and less fertile. The present paper records the results of the study of certain other characteristics of inflorescences and their influence on the productiveness of varieties. [The journal for July (I6: 475-570) was issued Sept. 4, I929.]