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The pollen size variations seen among the cultivars of Ananas comosus (Bromeliaceae) and the differences seen in wall reticulations of A. comosus and A. bracteatus are recorded. Among the different cultivars the pollen viability was between 24-92% according to the peroxidase and acetocarmine tests. With selfing, the pollen tubes grew to a maximum of about 13% of the stylar length in about eight hours after pollination. Results obtained, in two different media, regarding in vitro percentage germination and tube length are compared. The additions of various hormones and vitamins improved pollen tube growth but not germination. The reciprocal cross between cultivars resulted in seed formation, and the highest number of seeds was obtained with MasmerahxMauritius crosses. The results of the present study are compared with relevant literature

We study the application of the geographic nearest neighbor approach to two problems. The first problem is the construction of an approximately minimum length rectilinear Steiner tree for a set ofn points in the plane. For this problem, we introduce a variation of a subgraph of sizeO(n) used by YaO [31] for constructing minimum spanning trees. Using this subgraph, we improve the running times of the heuristics discussed by Bern [6] fromO(n2logn) toO(n log2n). The second problem is the construction of a rectilinear minimum spanning tree for a set ofn noncrossing line segments in the plane. We present an optimalO(n logn) algorithm for this problem. The rectilinear minimum spanning tree for a set of points can thus be computed optimally without using the Voronoi diagram. This algorithm can also be extended to obtain a rectilinear minimum spanning tree for a set of nonintersecting simple polygons.

The concentrations of nine heavy metals, cadmium, cobalt, copper, iron, manganese, nickel, lead, zinc and mercury in 42 Chinese herbal medicinal plants were determined. Generally, all the samples studied had, relative to the other trace metals, higher concentrations of iron, manganese, and zinc. The concentration range of the metals determined was comparable to that in many of the East Asian vegetables and fruits. A few samples were found to contain relatively higher concentrations of the toxic metals such as cadmium, lead, and mercury. This was probably caused by contamination during air-drying and preservation.

The vegetative apex of the Masmerah cultivar of pineapple, Ananas comosus(L.) Merr., is dome‐shaped and has the typical tunica‐corpus organization. Treating the plant with acetylene, NAA or ethephon transforms the vegetative apex to a reproductive one. As early as two days after treatment the apical height and width increase, attaining maximum dimensions in 8–14 days, after which they progressively decrease. During 4–6 weeks, when the full complement of florets has been initiated, the dimensions of the apex are again increased and leaves that form the fruit crown are initiated. A cambium‐like zone at the base of the corpus is noticed 2–4 days after the application of acetylene and ethephon. Acetylene and NAA result in a more pointed apex initially, while ethephon results in a more broadened apex. The largest increase in apical height and width is seen when NAA is used. The development of the inflorescence from the time the full complement of florets is formed to fruit maturity is described. Cell multiplication is the main cause of peduncle elongation and inflorescence head enlargement, although towards the later stages of growth, cell enlargement contributes more to the increase in size of the organs.

The single-facility location model with Euclidean distances and its multifacility and ℓp distance generalizations are considered. With present algorithms a user is unable to decide how close to optimal any given feasible solution is. This article describes two procedures for calculating a lower bound on the optimal objective function when a proposed solution is given.

Second generation aposporous gametophytes were obtained from sporophytes derived from first generation aposporous gametophytes, which in turn came from the mature fronds grown from spores in the laboratory. Murashige and Skoog modified medium in 1% agar supplemented with sugar alcohols (sorbitol, mannitol), auxins (NAA, 2,4-D) and cytokinin (BA) promoted a higher percentage of aposporous development from mature fronds ofPyrrosia piloselloides derived from aseptically cultured spores as compared with those obtained from plants in the field. A method using 4'6-diamidino-2-phenyl indole and fluorescence microscopy correlated the deoxyribonucleic acid contents of the aposporous gametophytes and sporophytes derived from them with their ploidy level.

Abstract: Pyrrosia piloselloides (L.) Price is a constitutive CAM plant in the sporophytic phase of its life-cycle. Newly developed sporophytes, still attached to the gametophytes, showed signs of CAM expression in terms of diurnal changes in titratable acidity of the tissues. The gametophytes did not exhibit CAM.

Abstract: Murashige and Skoog's modified medium in 1% Difco Bacto-agar supplemented with sugar alcohols (sorbsitol, mannitol), growth regulators (1-naphthalenacetic acid, 2,4-dichlorophenoxyacetic acid, benzyladenine, kinetin) and sugars (fructose, glucose, sucrose) induced aposporous gametophytes from pinnae of Pteris vittata cultured in vitro at lower concentrations of all the mentioned components. Aposporous gametophytes and vegetative calli were produced at higher concentrations. The calli regenerated sporophytes when cultured on MS medium without growth regulators. The gametophytes grew vegetatively on MS medium but produced sporophytes when transferred into 0.1 strength MS medium. This is the first report of simultaneous production of calli and gametophytes from fern explants.

Strips of Drymoglossum piloselloides fronds in a modified Murashige and Skoog medium in 1% agar produced aposporous gametophytes in about 2 months. Young fronds showed a greater ability to develop aposporous gametophytes than older fronds. The addition of kinetin to the medium improved the ability of older fronds while the presence of 1-naphthaleneacetic acid enhanced the effect of kinetin.