DEVELOPMENT OF THE DIMORPHIC CHLOROPLASTS OF SUGAR CANE

The vascular bundle sheath cells of sugar cane contain starch-storing chloroplasts lacking grana, whereas the adjacent mesophyll cells contain chloroplasts which store very little starch and possess abundant grana. This study was undertaken to determine the ontogeny of these dimorphic chloroplasts. Proplastids in the two cell types in the meristematic region of light-grown leaves cannot be distinguished morphologically. Bundle sheath cell chloroplasts in tissue with 50% of its future chlorophyll possess grana consisting of 2-8 thylakoids/granum. Mesophyll cell chloroplasts of the same age have better developed grana and large, well structured prolamellar bodies. A few grana are still present in bundle sheath cell chloroplasts when the leaf tissue has 75% of its eventual chlorophyll, and prolamellar bodies are also found in mesophyll cell chloroplasts at this stage. The two cell layers in mature dark-grown leaves contain morphologically distinct etio-plasts. The response of these two plastids to light treatment also differs. Plastids in tissue treated with light for short periods exhibit protrusions resembling mitochondria. Plastids in bundle sheath cells of dark-grown leaves do not go through a grana-forming stage. It is concluded that the structure of the specialized chloroplasts in bundle sheath cells of sugar cane is a result of reduction, and that the development of chloroplast dimorphism is related in some way to leaf cell differentiation.     

甘蔗雌雄蕊的解剖学研究

甘蔗雄蕊花药的壁由四层细胞构成,药室内壁在花药成熟时才发育。花粉母细胞减数分裂属连续型,四分体正常发育为小孢子,但当开花时,只有少数进一步发育为成熟的花粉粒。甘蔗雌蕊柱头是分枝的,每一柱头毛是由数个细胞质浓密的细胞,呈不规则的纵列而组成。倒生胚珠一个,着生于子房室的内侧;内、外珠被均由两层细胞构成,外珠被上侧未能生长到珠孔,内珠被的内层细胞在胚珠发育中不断增大体积。石蜡制片是以樟油为透明剂的。     

不溶性着色蔗渣木聚糖检测木聚糖酶活性*

蔗渣木聚糖经1.4-丁二醇二环氧甘油醚与染料气巴蓝3GA交联形成不溶性着色固体。这种着色蔗渣木聚糖在pH4-8范围内表现稳定,用于评价木聚糖酶活性及在平板上检测产酶微生物具有简捷而灵敏的效果。     

FROM SUGAR CANE TO 'SWORDS': HOPE AND THE EXTENSIBILITY OF THE GIFT IN FIJI

Hope has recently emerged as an important subject of inquiry in anthropology and social theory. This article examines the hope entailed in efforts to extend aspects of gift-giving to various other social and theoretical projects. I identify and contrast two different kinds of hope found in these efforts, which I will call 'hope in an end' and 'hope in the means'. The discussion focuses on two extensions of indigenous Fijian gift-giving: John D. Kelly and Martha Kaplan's recent analysis of Indo-Fijian sugar cane farmers'gift' of cane to an indigenous Fijian high chief in 1944; and the Fiji government Ministry of Tourism's efforts in the mid-1990s to train indigenous Fijian souvenir traders in a properly 'Fijian' manner of engagement with tourists. With this contrast, I argue that 'hope in an end' occludes 'hope in the means'.     

INORGANIC NITROGEN NUTRITION OF THE SEEDLINGS OF THE ORCHID,CATTLEYA

When grown in vitro in a medium containing NH₄NO₃ as the sole source of nitrogen, seeds ro the orchid, Cattleya (C. labiata ‘Wonder’ X C. labiata ‘Treasure'), germinated readily and proceeded to form small plantlets. Development of the embryos was accompanied by an increase in their total nitrogen and a decline in the percent dry weight. Growth responses of the seedlings in other ammonium salts like (NH₄)₂SO₄, (NH₄)₂HPO₄, NH₄Cl, ammonium acetate and ammonium oxalate were similar to that in NH₄NO₃. However, when grown in a medium containing NaNO₃, development of the seedlings was drastically inhibited; KNO₃, Ca(NO₃)₂, KNO₂ and NaNO₂ also were poor nitrogen sources. Attempts to grow the seedlings in NaNO₃ by changing the pH or by addition of kinetin, molybdenum or ascorbic acid as supplements were completely unsuccessful. When seedlings growing in NH₄NO₃ for varying periods were transferred to NaNO₃, it was found that those plants allowed to grow for 60 or more days in NH₄NO₃ could resume normal growth thereafter in NaNO₃. Determination of the nitrate reductase activity in seedlings of different ages grown in NaNO₃, after NH₄NO₃, showed that the ability of the seedlings to assimilate inorganic nitrogen was paralleled by the appearance of the enzyme.