Abscisic Acid Enhances the Ability of the Desiccation-Tolerant Fern Polypodium virginianum to Withstand Drying

Detached fronds of Polypodium virginianum L. survived loss of65–70% of their fresh weight over 10 d of slow-drying.Drying over silica gel resulted in a faster rate of water loss,to a lower fresh weight, which the fronds did not survive. Whenfronds were incubated in abscisic acid for 24 h prior to silica-drying,the amount of water lost was reduced, resulting in survivalof the fronds upon subsequent rehydration. Incubation in abscisicacid for at least 18 h was necessary for survival. Fronds inwhich the final fresh weight after drying was below a criticalamount (i.e. to less than 25% original fresh weight) did notsurvive. A reasonable correlation could be drawn between electrolyteleakage upon rehydration and survival of somedesiccation treatments,although this was not always clear-cut, especially in frondsincubated in abscisic acid for an insufficient time to ensuresurvival. Several polypeptides were synthesized during slow-and silica-drying, and in response to abscisic acid. No novelpolypeptides were identified that were unique to the desiccationregimes which resulted in survival. Nor did ABA induce specificproteins in fronds desiccated after preincubation in this regulatorfor 24 h. Key words: Desiccation-tolerance, abscisic acid, protein synthesis, fern, Polypodium virginianum     

Estimating sib percentages from small samples of F1 hybrid populations

Plant breeders raising F_x hybrid populations cannot usually grow more than about 300 plants from one seed lot. If not more than k sibs are observed in a random sample of size N, they then need to estimate the probability that the proportion of sibs in the population is at most p. For sample sizes of not more than 300 this note describes the required statistical procedure which, though not new, may be unfamiliar to plant breeders.     

The Role of Maturation Drying in the Transition from Seed Development to Germination: I. ACQUISITION OF DESICCATION-TOLERANCE AND GERMINABILITY DURING DEVELOPMENT OF Ricinus communis L. SEEDS

Kermode, A. R. and Bewley, J. D. 1985. The role of maturationdrying in the transition from seed development to germination.1. Acquisition of desiccation–tolerance and germinabilityduring development of Ricinus communis L. seeds.—J. exp.Bot. 36: 1906–1915. Seeds of Ricinus communis L. cv. Hale(castor bean) undergo a transition from desiccation–intoleranceto desiccation–tolerance approximately midway throughtheir development. Tolerance of slow desiccation is gained overonly a few days of development (between 20 and 25 d) and isachieved well before the completion of major developmental events,such as reserve deposition and the onset of normal maturationdrying. A tolerance of very rapid water loss brought about bydrying over silica gel is not acquired by this seed until nearmaturity. Coincident with the acquisition of tolerance to slowdesiccation the seeds gain the capacity to germinate upon subsequentrehydration. Germinability and capacity for normal post–germinativegrowth during the tolerant phase are not fully expressed unlessthe seed is dried at an optimal rate, which is dependent uponthe developmental stage of the seed. Drying presumably actsto terminate developmental processes and to initiate those metabolicprocesses necessary to prepare the seed for germination andgrowth. Key words: Desiccation-tolerance, germinability, seed development, castor bean     

Growth models and the expected distribution of fluctuating asymmetry

Multiplicative error accounts for much of the size-scaling and leptokurtosis in fluctuating asymmetry. It arises when growth involves the addition of tissue to that which is already present. Such errors are lognormally distributed. The distribution of the difference between two lognormal variates is leptokurtic. If those two variates are correlated, then the asymmetry variance will scale with size. Inert tissues typically exhibit additive error and have a gamma distribution. Although their asymmetry variance does not exhibit size-scaling, the distribution of the difference between two gamma variates is nevertheless leptokurtic. Measurement error is also additive, but has a normal distribution. Thus, the measurement of fluctuating asymmetry may involve the mixing of additive and multiplicative error. When errors are multiplicative, we recommend computing log  E ( l ) − log  E ( r ), the difference between the logarithms of the expected values of left and right sides, even when size-scaling is not obvious. If l and r are lognormally distributed, and measurement error is nil, the resulting distribution will be normal, and multiplicative error will not confound size-related changes in asymmetry. When errors are additive, such a transformation to remove size-scaling is unnecessary. Nevertheless, the distribution of l  −  r may still be leptokurtic.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80, 57–65.