STD 12 - 1. sexual reproduction in flowering plants — NEET STD 11 Science — Question

Four chromatids and two centromeres which are homologous occurs in

To show how many organisms are present at each level of a food chain, ecologists use a model called

The tissue which participates in the secondary growth is

The pyramid of biomass in sea is generally inverted because...

The scutellum observed in a grain of wheat or maize is comparable to which part of the seed in other monocotyledons?

Ulothrix produces

Which one of the following statements are correct ?
(i) In monocotyledons, the leaf base expands into a sheath covering the stem partially or wholly
(ii) In some monocotyledons plants the leaf base may become swollen, which is called the pulvinus.
(iii) Veins provide rigidity to the leaf blade and act as channels of transport for water, minerals and food materials.
(iv) The arrangement of veins and veinlets in the lamina of leaf is termed as venation.
(v) Leaves of dicotyledonous plants generally possess reticulate venation, while parallel venation is the characteristic of all monocotyledons.
(vi) When the incision of the lamina reach up to the midrib breaking it into a number of leaflets, the leaf is called compound.
(vii) In palmately compound leaf a number of leaflets are present on a common axis, the rachis, which represent the midrib of leaf.
(viii) In pinnately compound leaves, the leaflets are attached at a common point, i.e., at the tip of petiole, as in silk cotton.
(ix) Phyllotaxy is the pattern of arrangement of leaves on the stem or branch.
(x) In cymose type of inflorescence the main axis terminates in a flower.
(xi) The flowers are borne in a Acropetal order in cymose inflorescence.
(xii) In lily, the calyx and corolla are not distinct and are termed as perianth.
(xiii) When a flower can be divided into two equal halves in any radial plane passing through the centre, it is said to be actinomorphic.
(xiv) Based on symmetry, flower of Cassia and mustard are zygomorphic.
(xv) In racemose inflorescence flowers are borne in an basipetal succession.
Choose the correct option given below :-

Choose incorrect sentence.

Which of the following are salient features of genetic code ?

Choose correct statement for cytokine and mark correct option :
(i) It is a simple gaseous PGR.
(ii) It synthesised in large amounts by tissues undergoing senescence and ripening fruits.
(iii) Influences of it on plants include horizontal growth of seedlings, swelling of the axis and apical hook formation in dicot seedlings.
(iv) It promotes senescence and abscission of plant organs especially of leaves and flowers.
(v) It synthesised in regions where rapid cell division occurs, for example, root apices, developing shoot buds, young fruits, etc.
(vi) It helps to produce new leaves, chloroplasts in leaves, lateral shoot growth and adventitious shoot formation.
(vii) It help overcome the apical dominance.
(viii) They promote nutrient mobilisation which helps in the delay of leaf senescence.