General Agriculture & Statistics

Phytochrome (discovered by Borthwick and Hendricks at USDA Beltsville) is a soluble chromoprotein photoreceptor that perceives daylength (photoperiod) and mediates floral induction, seed germination, and shade avoidance.
It exists in two interconvertible conformational states:

The active $P_{fr}$ form interacts with transcription factors (such as CONSTANS and Flowering Locus T / florigen) in leaf leaves to trigger flowering.

The institutional process for commercializing a new crop variety under the AICRP/ICAR system follows a defined sequential pathway:

• Development of an improved stable strain/genotype by the plant breeder through selection or hybridization (B).
• Multi-location evaluation across agro-climatic zones under AICRP testing (Initial Varietal Trial - IVT, followed by Advanced Varietal Trials - AVT-I and AVT-II) for 3 years (C).
• Identification of the candidate variety based on superior yield, disease resistance, and quality data during the Annual All India Crop Workshop by the Varietal Identification Committee (VIC) (A).
• Formal Release and Notification under Section 5 of the Seeds Act (1966) by the Central Sub-Committee on Crop Standards, Notification and Release of Varieties (CSCSNRV) for commercial seed production and sale (D).

The biological sequence from pollination to fruit maturation is:

• Pollination & Tube Growth (B): Pollen grain lands on receptive stigma, hydrates, germinates, and sends the pollen tube down through the style toward the ovary micropyle.
• Syngamy / Fertilization (D): Generative male gamete nucleus descends the tube and fuses with the egg cell nucleus to accomplish fertilization.
• Seed Maturation (A): The fertilized, diploid ovule differentiates into the mature seed containing embryo and endosperm.
• Fruit Ripening (C): Stimulated by auxin and gibberellins from the developing seeds, the surrounding ovary wall (pericarp) expands, ripens, and transforms into the fruit.