A leaf of a plane tree is called an old leaf if it is the leftmost child of its parent, and it is called a young leaf otherwise. In this paper we enumerate plane trees with a given number of old leaves and young leaves. The formula is obtained combinatorially by presenting two bijections between plane trees and 2-Motzkin paths which map young leaves to red horizontal steps, and old leaves to up...

Plants of nutrient-poor, arid environments often have leaf traits that include small size, sclerophylly, long life span, low nutrient concentration, and low photosynthetic rate. Hence, the success of two large-leaved palmettos in peninsular Florida's seasonally xeric, nutrient-impoverished uplands seems anomalous, given that their leaves are orders of magnitude larger than the leaves of sympatr...

to evaluate the effect of environment on the general and specific combining ability of virginia tobacco genotypes, five varieties were intercrossed in combination in 2007 in a half – diallel design. in 2008, the ten f1 population and the five parental lines were sown in two different conditions (drought stress and non-stress) using a complete randomized block design with three replications and ...

The effects of Bt transgenic cottons (Bt-I expressing cry1Ac and Bt-II expressing cry1Ab and cry2Ab or cry1Ab and cry1Fa) and non-Bt cottons on feeding, oviposition and longevity of adults, and development and survival of Liriomyza trifolii larvae were studied under laboratory conditions; and infestation on four Bt and two non-Bt cotton traits were investigated under field conditions. Laborator...

The evolution of visual warning signals is well known in animals but has received scant attention in plants. The coevolutionary hypothesis is the most influential hypothesis on warning signals in plants proposing that red and yellow leaf colours in autumn signal defensive strength to herbivores. So far, evidence in support of the hypothesis, which assumes a coevolutionary origin of autumnal lea...

kochia is a halophyte plant and is a good source of forage for livestock under saline irrigation. in order to investigate the salinity effect on morphological and forage characteristics of kochia, an experiment was conducted. three saline waters (5.2, 10.5 and 23.1 ds m-1) and three kochia ecotypes (birjand, borujerd and sabzevar) were allocated as main and sub plots, respectively, in a split p...

Preplant soil applications of oxamyl to shade grown tobacco in Globodera tabacum-infested field soil increased green leaf yields over untreated plots by 10.7 and 21.0% for 2.2 and 6.7 kg a.i. oxamyl/ha, respectively. Green leaf yield was negatively correlated (r = -0.60, P = 0.04) with initial G. tabacum density, which ranged from 33 to 154 second-stage juveniles (J2)/cm(3) soil. Numbers of G. ...

This paper contributes to the solution of the Poincaré problem, which is to bound the degree of a (generalized algebraic) leaf of a (singular algebraic) foliation of the complex projective plane. The first theorem gives a new sort of bound, which involves the Castelnuovo–Mumford regularity of the singular locus of the leaf. The second theorem gives a bound in terms of two singularity numbers of...