Endosperm cell number in barley
Grain weight is one of the major components of grain yield and it has been suggested that in wheat, final grain weight may be a function of endosperm cell number1. If grain weight is to be increased by increasing the rate and/or duration of endosperm cell division, it is important to establish the stage of development at which maximum endosperm cell number is attained. Evers2 reported that no cell division occurred in the endosperm of wheat later than 16 days after anthesis and other workers3,4 have come to a similar conclusion using cell counts. However, biochemical analyses5 have shown that the maximum DNA content of wheat endosperm is not reached until 25 days after anthesis and both Donovan6 and Radley7 have suggested that endosperm cell division may continue until about 30 days after anthesis. We have estimated the number of endosperm nuclei in developing caryopses of barley and have examined transverse sections of endosperms of different ages. We report here that cell division in barley endosperm continues until 28–30 days after anthesis.
Alteration of Leaf Anatomy of Mangosteen (Garcinia mangostana L.) Regenerants In Vitro by Gamma Irradiation
The mangosteen plant has a low rate of photosynthesis which is known indirectly through its leaf anatomy. We conducted a study on the effect of gamma irradiation on the alteration of leaf anatomy of 21 mutant regenerants obtained from irradiated nodular calli and compared it with a non-irradiated regenerant. Whole mount leaf stained with 1% saffranin showed an increased stomatal width, density, and index as well as epidermal cells density in most mutant regenerants compared with the controls. Transverse sections (10 μm) of leaf of mutant regenerants obtained by staining with 1% safranin and 0.5% fastgreen and sliced with microtome also revealed a generally thinner upper and lower cuticle than the controls. Transverse section of mutant lines R-10/4, R-15/1, R-15/2, R-15/3 had thicker palisade, spongy parenchyma and leaf lamina than the control regenerant. Also, the number of vascular bundles was higher than control. A thinner upper cuticle coupled with high stomatal density and index may enhance penetration of incident light as well as easy diffusion of carbon dioxide into the leaf. Similarly, much thicker palisade and spongy parenchyma may increase the number of chloroplasts in the mutants and therefore indirectly increase photosynthetic efficiency.
Studies on the Ripening of Wheat Grain : 2. Development of the Endosperm Tissue. : 3. Development of the Starch Grain and Reserve Protein Particle in the Endosperm.
Based on the anatomical studies of the wheat grains which were sampled everyday beginning from the day of anthesis to the maturity, the stages of development of the endosperm were classified under 13 heads as follows (parenthesized figures show the days after anthesis under natural condition): Stage I, division of endosperm mother cell (∼1). Stage II, multiplication of endosperm nuclei (1-3). Stage III, cell membrane formation (4). Stage IV, the peripheral cell layer formation (5). Stage V, filling up of the embryo sac cavity (6). Stage VI, deposition of the "first type" starch grains (7). Stage VII, stop of cell division at the inner part of endosperm (11). Stage VIII, deposition of the "second type" starch grams (17). Stage IX, end of cell division in an entine endosperm (18). Stage X, enlarging of the endosperm cells (20). Stage XI, beginning of maturation from inner part of endosperm (30). Stage XII, completion of cell growth (37). Stage XIII, constriction of tissue (40). During the early stages (V-VII) of development, the cell divisions proceed not, only at outer zone of endosperm tissue but also at inner zone. The cell division of the most exterior cell layer ceases lastly and matures as the aleuron layer by about 20 days after anthesis. From the stage X onwards, the cells elongate into cylindrical form at the bridge, while they enlarge into spherical polygons at the flank. Starch grains reserved in every cell are of two types. The "first type" grams are deposited during early stages (VI∼) and all the grains becolne large and uniform in size, and lenticular in appearance. The "second type" grains appear in the same cells about 10 days later than the first type grains, and continue to increase in number extending over a long period. However, they grow only a little in size and become spherical in shape. Reserve protein particles (gluten) are deposited in the cytoplasma by 10∼13 days after anthesis, and thereafter they grow in form which are indeterminate by increasing their volume. These protein particles are more abundantly found in the hard variety than in the soft one.