Net carbon dioxide exchange rates in Pisum sativum L as influenced by phosphorus and nitrogen nutrition

Two varieties of Pisum sativum, L, Jade and Olympic, were grown for a period of four weeks from seeding, under constant light intensity and diurnally fluctuating temperatures, while being subjected to varying-artificially induced-degrees of nutrient stress. Net carbon dioxide exchange rates were measured in order to determine the influence of excess or deficient nitrogen and phosphorus concentrations within the nutrient medium. Carbon dioxide assimilation rates, under various degrees of nutrient stress were highly variable, both within the same variety and between varieties tested. Microchemical determinations of chlorophylls a and b, and of inorganic phosphate, nitrate and nitrite were carried out in order to determine the relationship of some physiological aspects of mineral deficiency to carbon dioxide assimilation. Investigations as to changes in stomatal index (I) as a result of nutrient stress also showed a large amount of variation. Results obtained indicated that variety Jade was very sensitive to nitrogen deficiency within the rooting medium, as evidenced by a large increase in stomatal index values with nitrogen deficiency. Olympic showed a greater sensitivity to phosphorus deficiency than did Jade. Neither total chlorophyll content, nor chlorophyll a/b ratio appeared to exert any deciding influence upon net carbon dioxide assimilation. A relationship appeared to exist between CO₂ assimilation and quantities of nitrate and/or nitrite present within the photosynthetic tissues of plants tested. This experiment was unable to fully explain the reason(s) for the great degree of variability of net CO₂ exchange rates extant even between plant specimens growing in the same nutrient medium. Some technical improvements applicable to the present experiments as well as some alternative experimental procedures are discussed.Land and Food Systems, Faculty ofGraduat

Efficient Generation of Subsets with a Given Sum

Let C(n, p) denote the set of all subsets of {1, 2, ..., n} whose sum is p, and let C(n, k, p) denote the k element sets of C(n, p). We show that the elements of C(n, p) and C(n, k, p) can be generated efficiently by a simple recursive algorithms. The subsets are represented by characteristic bitstrings and by lists of elements. These representations can be generated in time that is proportional to the number of subsets generated

On Rotations and the Generation of Binary Trees

The rotation graph, G n , has vertex set consisting of all binary trees with n nodes. Two vertices are connected by an edge if a single rotation will transform one tree into the other. We provide a simpler proof of a result of Lucas [7] that G n contains a Hamilton path. Our proof deals directly with the pointer representation of the binary tree. This proof provides the basis of an algorithm for generating all binary trees that can be implemented to run on a pointer machine and to use only constant time between the output of successive trees. Ranking and unranking algorithms are developed for the ordering of binary trees implied by the generation algorithm. These algorithms have time complexity O(n 2 ) (arithmetic operations). We also show strong relationships amongst various representations of binary trees and amongst binary tree generation algorithms that have recently appeared in the literature. Current address: SUNY Brockport, Mathematics & Computer Science Dept., Brockport, ..

On Parallel Generation of t-ary Trees in an Associative Model

In this paper a new parallel algorithm is presented for generation of t--ary trees. Computations run in an associative processor model

Hamiltonian paths for involutions in the square of a Cayley graph

International audienc

A Parallel Dynamic Programming Algorithm for Unranking t-ary Trees

In this paper an O(n) parallel algorithm is presented for fast unranking t--ary trees with n internal nodes in Zaks' representation