BIOCHEMICAL AND PHYSIOLOGICAL ASPECTS OF LEAF DEVELOPMENT IN COCOA (THEOBROMA CACAO)

The dormant phase of the flush cycle of leaf growth in cocoa is known to be correlated with high abscisic acid (ABA) levels in the mature leaves of the new flush (NF) and previous flush (PF) leaves. Defoliation of either the NF leaves or PF leaves of cocoa seedlings reduced the length of the dormant phase of the flush cycle, thus showing that the mature leaves were a source of growth inhibitors which could affect shoot apical activity. The application of ABA to the NF and PF leaves led to an extension of the dormant phase, whereas application of zeatin or gibberellic acid decreased it. The distribution of [¹⁴C]ABA following its application to NF and PF leaves at different stages throughout the growth cycle showed that [¹⁴C] ABA was accumulated by the bud in relatively larger amounts during the final stages of bud dormancy (I-1 and I-2) than in the earlier stage (F-2). The results suggest that internal competition for nutrients may be responsible for the inhibition of growth at the F-2 stage but that ABA translocated from the mature leaves causes the buds to remain dormant during the subsequent stages of I-1 and I-2.     

THE SHOOT-GROWTH RHYTHM OF A TROPICAL TREE,THEOBROMA CACAO

The shoot-growth rhythm of tropical trees is a little understood phenomenon. Correlations of tree growth with environment, determined from field studies in the tropics, have been largely inconclusive, and few studies have been done under controlled environmental conditions. As an initial part of a project to study shoot-growth rhythms in tropical trees this paper describes the rhythm in Theobroma cacao L. An individual shoot passes through alternate periods of growth and dormancy. The growth period is characterized by the expansion of leaves and elongation of the shoot. During dormancy the length of the shoot remains constant, and no new leaves expand. Shoot-growth rhythm was divided into phases. Dissection of shoot tips from the various phases shows that the total number of leaves and leaf primordia in the shoot apex remains constant during the dormant period and does not increase until the onset of the growth period. This indicates that activity of the apical meristem as well as leaf expansion and shoot elongation are rhythmic. We found that the rhythm of shoot growth persists under controlled environmental conditions and that growth under these conditions is asynchronous, as it appears to be in the field. Our data strongly suggest endogeneity.     

STUDIES ON THE HOST RANGES OF VIRUSES FROM THEOBROMA CACAO L.

Only plants in the natural order Tiliales were susceptible to experimental infection by viruses found infecting cacao. Of sixty-three species in the Tiliales colonized with infective mealybugs, twenty-eight became infected with the New Juaben virus. The ease with which different species contracted infection and the severity of symptoms varied considerably. The host ranges of seven other viruses were all contained in that of the New Juaben virus. The viruses could be divided into three groups according to their host ranges, and it is suggested that host ranges may prove helpful in attempts to classify cacao viruses. Four species of Corchorus were all rapidly killed by any of the eight viruses.     

中国对虾雄性生殖系统的结构及发育

本文较详细地叙述中国对虾雄性生殖系统的结构,与以前作者描述的有异。其精巢为分叶状;输糟管中段和分泌管道共处于同一圆管之内;生殖管道上皮多有分泌功能。在一次发育期中精子的发生大约持续两个月,产生的精子量大;雄虾具有多次交配的能力。     

STRUCTURE AND DEVELOPMENT OF THE SHOOT IN DOLICOTHELE

Boke , Norman H. (U. Oklahoma, Norman.) Structure and development of the shoot in Dolicothele. Amer. Jour. Bot. 48(4): 316–321. Illus. 1961.—A study of 2 species of Dolicothele reveals that although they have dimorphic areoles and a pattern of spine development similar to those of certain mammillarias, they share a significant number of ectomorphic and endomorphic characters with coryphanthas of the “vivipara group.” These include a tendency toward a cespitose habit; relatively large flowers; green fruits; pitted seeds; medullary vascular systems; forking of the main tubercle traces in the bases of the tubercles; lack of mucilage cells; thin-walled epidermis and hypodermis, both devoid of crystals; and large, druse-like crystalline aggregates in older parts of the pith and cortex. The evidence suggests that Coryphantha vivipara and closely allied species are the nearest extant relatives of Dolicothele. It would, therefore, seem inconsistent to return Dolicothele to Mammillaria unless an author's viewpoint were so conservative that he was willing also to return most, if not all, coryphanthas and escobarias to that genus.     

SUBMICROSCOPIC STRUCTURE AND DEVELOPMENT OF THE CHLOROPLASTS OF PSILOTUM TRIQUETRUM

Sun , C. N. (Washington U., St. Louis, Mo.) Submicroscopic structure and development of the chloroplasts of Psilotum triquetrum. Amer. Jour. Bot. 48(4): 311–315. Illus. 1961.—Aerial stems and stem tips of Psilotum triquetrum were used for the study of the fine structure and development of chloroplasts. The chloroplasts of Psilotum are ellipsoidal, with a principal axis of approximately 13 μ and a short axis of approximately 3.6 μ. They are bounded by a well-defined outer membrane which consists of 2 layers. Within the laminar system of the stroma, the lamellated grana appear as sharply defined regions. The grana are about 1–1.6 μ in diameter. They are distributed more or less uniformly throughout the entire chloroplast with the exception of a very narrow peripheral zone. Relatively large, osmiophilic globules occur in groups in the stroma. The development of the Psilotum chloroplast may be summarized as follows: (1) in the undifferentiated proplastid, vesicles occur; (2) lamellated layers are formed by the fusion of vesicles; (3) the lamellae multiply by a process of thickening and splitting; (4) the grana are differentiated within a certain area by heterogeneous deposition of material and by further cleavage of the lamellae. Osmiophilic globules are present throughout the developmental stages, and increase in number and size with increase in age of the chloroplast.